Monday, August 16, 2010

Chevy P30 Chassis manual & link to my 83 Pace Arrow refurbishing blog

Follow this link for the chassis manual: The manual is 294 pages, too long to post each page on this site, and being it is a PDF file you can print it directly form this site if you want to. I have attached the 294 pages below , but you would still benefit from going to the listed website to get it in the original format, which will include photos and diagrams, being it is too long for me to attempt to edit:


http://bdub.net/manuals/P30/P30.pdf

Also I have provided another link to my restoration  / refurbishing blog on my 83 Pace Arrow for your review, see below:

http://1983pacearrowmotorhomerestoration.blogspot.com/


MOTOR HOME
GUI
FOREWORD
This manual has been developed to provide the owner and operator with service information for the Chevrolet motor home chassis. Major components and systems are described and maintenance and inspection procedures are given . In addition to providing information for proper maintenance of the motor home chassis, some inspection and diagnosis procedures are included to help detect and identify common .problem conditions which may occur.
In a section at the end of this manual are appendixes containing additional information helpful in maintaining the motor home. This includes information on drive belts, storage of the motor home, identification for nuts and bolts, and formulas for converting to metric measurements.
The organization of the Chevrolet Motor Home Chassis Service Guide is similar to that of the Chevrolet Light-Duty Truck 10-30 Series Shop Manual . While the information contained in this Service Guide is intended to establish proper maintenance and inspection procedures, there may be times when more detailed diagnostic and repair procedures contained in the Shop Manual may be required. The similarity in organization can make reference to the Shop Manual easier.
Specific references to Chevrolet Service Bulletins have been included within the text and appendixes of various sections of this manual . Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer." They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions,and know-how to do a job properly and safely. If a condition is described,DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will
have that condition . See your Chevrolet dealer for information on whether your vehicle may benefit from that information .
SUGGESTIONS FOR IMPROVED SERVICE
Motor homes can only service the needs of their owners when they are in dependable operating condition and able to perform properly. Costly breakdowns, service calls and downtime expense can be minimized through properly performed regular maintenance.
Therefore, you should become familiar with Chevrolet's maintenance recommendations which have been developed in the interest of maximum vehicle
performance and economical operation by those best qualified . These recommendations are outlined in the General Motors Maintenance Schedule for Light-Duty Trucks which was furnished with your Chevrolet chassis .
WHEN TRAVELING, CHEVROLET RECOMMENDS THE FOLLOWING TO OBTAIN SERVICE :
1 . Wherever you are traveling, look in the yellow pages to see if there is a local Chevrolet dealership. Call the local dealership and ask to talk to the service manager. Tell him, as specifically as possible, the nature of your problem(s) . Often, even a small dealership with limited facilities will be able to perform some of the simpler tasks of a lube or oil filter change, or other minor repairs. If the local dealer is not able to assist you, he may know of reputable towing companies, neighboring Chevrolet dealerships and independent repair facilities who may be able to help. Often the Chevrolet dealer may assist a warranty situation via a
sublet through a local repair shop if the local Chevrolet dealer's shop cannot handle the necessary repairs .
2. If information is provided, motor home owners might call the RV manufacturer's service department. Based on prior positive experiences, the service department may be able to provide suggestions on where to take the vehicle, in that local area, for good repair work ; i.e., the RV manufacturer's nearest local coach dealer, Chevrolet dealers, or even independent repair facilities with a history of proper and competent repair experience on the motor home.
3. Or the motor home owner may need to contact the Chevrolet Customer
Assistance Center 1-800 FOR CHEV or (1-800-222-1020). When calling, be as
specific as possible regarding the nature of the problem. Ask for the name and telephone number of the nearest dealer who has a demonstrated interest and the facilities for repairing motor coaches. Remember to ask for the name of that dealership's service manager so that you may call him directly to determine if he is able and available to handle your particular motor home service needs.
4. 24 hour road side assistance Call 1-800 CHEV USA Canada 1-800 268 6800 roadside 1-800 263 3777 customer assistance
Heating System . . . . . . . . . . . . . . . . . . . . . . 2-1
General Description . . . . . . . . . . . . . . . . . 2-1
Troubleshooting the System . . . . . . . . . . 2-1
Air Conditioning System . . . . . . . . . . . . . . . 2-2
General Description '. . . . . . . . . . . . . . . . . 2-2 .
Receiver-Dehydrator . . . . . . . . . . . . . . . 2-2
Accumulator . . . . . . . . . . . . . . . . . . . . . 2-2
G-Series System . . . . . . . . . . . . . . . . . . . . 2-2-
P-Series System . . . . . . . . . . . . . . . . . . . . 2-4
Maintenance and Inspection . . . . . . . . . . 2-4
Refrigeration Section . . . . . . . . . . . . . . 2-4
Inspection . . . . . . . . . . . . . . . . . . . . . . . 2-4
Operational Quick Checks . . . . . . . . . . 2-4
Air Distribution Section . . . . . . . . . . . . . . . . 2-5
Electrical Circuit Diagnosis . . . . . . . . . . . 2-5
Vacuum System Diagnosis
(G-Series) . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Appendix 2-1 - Optional Air Conditioning
System . . . . . . . . . . . . . . . . 2-6
SECTION 3 - STEERING, SUSPENSION,
WHEELS AND TIRES . . . . . . . . 3-1
Front Alignment . . .. . . . . . . . . . . . . . . . . . . . 3-1
General Description . . . . . . . . . . . . . . . . . 3-1
Caster . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Camber . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Toe-In . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Maintenance and Inspection . . . . . . . . . . 3-2
Alignment Check . . . . . . . . .. . . . . . . . . 3-2
Frame Angle Measurement . . . . . . . . . 3-3
Lower Ball Joint Inspection . . . . . . . . . 3-3
Steering System . . . . . . . . . . . . . . . . . . . . . . 3-4
Steering Linkage . . . . . . . . . .. . . . . . . . . . . 3-4
General Description . . . . . . . . . . . . . . . 3-4
Maintenance and Inspection . . . . . . . . 3-4
Lubrication of Steering Linkage . . . . 3-4
Steering Linkage Support Assemblies
(P-Series) . . . . . . . . . . . . . . . . . . . . . . 3-4
Steering Damper Check . . . . . . . . . . 3-4
TABLE OF CONTENTS
Table - 1
Spring/Air Bag Replacement . . . . . . 3-9
Shock Absorber Diagnosis . . . . . . . 3-10
Rear Suspension . . . . . . . . . . . . . . . . . . 3-12
General Description . . . . . . . . . . . . . . 3-12
Maintenance and Inspection . . . . . . . 3-12
Wheels and Tires . . . . . . . . . . . . . . . . . . . . 3-13
General Description . . . . . . . . . . . . . . . . 3-13
Maintenance and Inspection . . . . . . . . . 3-13
Tire Inspection and Rotation . . . . . . . 3-13
Inflation Pressure . . . . . . . . . . . . . . . . 3-13
Determining Wheel/Tire Loads . . . . . 3-13
Wheel and Tire Balancing . . . . . . . . . 3-14
Tire Replacement . . . . . . . . . . . . . . . . 3-13
Wheel/Stud Bolt Replacement . . . . . . 3-16
Typical Wheel and
Stud Bolt Failures . . . . . . . . . . . . . . . . 3-16
WornlBroken Stud Bolts . . . . . . . . . 3-16
Worn/Cracked Wheels . . . . . . . . . . 3-16
Bent Rim Check/Tire to
Rim Matching . . . . . . . . . . . . . . . . . . . 3-17
TIRE Wear -Tire Rotation . . . . . . . 3-18
Effect of Inflation . . . . . . . . . . . . . . 3-18
Effect of Overloading . . . . . . . . . . . 3-18
Effect of Overheating . . . . . . . . . . . 3-18
Appendix 3-1 - Steering Relay and Tie
Rod Parts Identification . 3-20
Appendix 3-2 - Typical Load Height
Curves . . . . . . . . . . . . . . . 3-21
SECTION 4 - PROPELLER SHAFTS AND
UNIVERSAL JOINTS . . . . . . . . 4-1
General Description . . . . . . . . . . . . . . . . . . . 4-1
Propeller Shafts . . . . . . . . . . . . . . . . . . . . 4-1
Universal Joints . . . . . . . . . . . . . . . . . . . . 4-1
Maintenance and Inspection . . . . . . . . . . . . 4-2
Typical Failures . . . . . . . . . . . . . . . . . . . . 4-2
Driveline Noise and/or Vibration Checks . 4-3
Driveline Balance Procedure . . . . . . . . . . 4-3
SECTION 1 - INTRODUCTION . . . . . . . . . . . . 1-1 Power Steering System . . . . . . . . . . . . . . 3-5
General Information . . . . . . . . . . . . . . . . . . . 1-1 General Description . . . . . . . . . . . . . . . 3-5
G-Series Motor Home Chassis . . . . . . . . . . 1-1 Maintenance and Inspection . . . . . . . . 3-5
P-Series Motor Home Chassis . . . . . 1-1, 1-1AB Hard Steering at Engine Idle . . . . . . 3-6
Identification Numbers . . . . . . . . . . . . . . . . 1-1 Leakage Check . . . . . . . . . . . . . . . . . 3-6
Vehicle Identification Number (VIN) . . . . 1-2 Quick Fixes . . . . . . . . .
. 3-7
Service Parts Identification Label . . . . . . 1-3 Pump Belt Tension Adjustment . 3-7
Motor Home Towing . . . . . . . . . . . . . . . . . . . 1-3 Suspension System . . . . . . . . . . . . . . . . . . . 3-8
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 Front Suspension . . . . . . . . . . . . . . . . . . . 3-8
Recommended Fluids and Lubricants . . 1-4 General Description . . . . . . . . . . . . . . . 3-8
Lubricant Capacities . . . . . . . . . . . . . . . . 1-5 Maintenance and Inspection . . . . . . . . 3-8
Lubrication Points - G-Series . . . . . . . . 1-6 Wheel Bearing Lubrication . . . . . . . . 3-8
Lubrication Points - P-Series . . . . . . . . . 1-6 Wheel Bearing
Lubrication Points - I-Beam Axle . . . . . . 1-7 Adjustment Check . . . . .. . . . . . . . . . 3-8
Wheel Bearing Adjustment . . . . . . . 3-8
SECTION 2 - HEATING AND Air Bag Cylinder Inspection . . . . . . . 3-9
AIR CONDITIONING . . . . . . . . 2-1 Vehicle Ride Height - Front Coil
TABLE OF CONTENTS (Cont'd)
Appendix 4-1 - Driveline Vibrations -
Appendix 4-1 - One and Two Drive Shaft
Systems . . . . . . . . . . . . . . . 4-6
Appendix 4-2 - Driveline Vibrations -
Three-Shaft Drivelines . . . . 4-8
SECTION 5 - REAR AXLE . . . . . . . . . . . . . . . 5-1
General Description . . . . . . . . . . . . . . . . . . . 5-1
Maintenance and Inspection . . . . . . . . . . . . 5-1
Differential Fluid . . . . . . . . . . . . . . . . . . . . 5-1
Wheel Bearing Adjustment
(Tapered Bearing) . . . . . . . . . . . . . . . . . . . 5-1
Wheel Bearing Adjustment
(Barrel-Type Bearing) . . . . . . . . . . . . . . . . 5-2
Axle Housing . . . . . . . . . . . . . . . . . . . . . . 5-3
Bent Axle Housing . . . . . . . . . . . . . . . . . . 5-3
SECTION 6 - BRAKES . . . . . . . . . . . . . . . . . . 6-1
General Description . . . . . . . . . . . . . . . . . . . 6-1
Disc Brakes . . . . . . . . . . . . . . . . . . . . . . . . 6-2
Drum Brakes . . . . . . . . . . . . . . . . . . . . . . . 6-3
Power Units . . . . . . . . . . . . . . . . . . . . . . . . 6-3
Parking Brake(s) . . . . . . . . . . . . . . . . . . . . 6-4
Maintenance and Inspection . . . . . . . . . . . . 6-5
Filling the Master Cylinder . . . . . . . . . . . . 6-5
Pedal Travel Check . . . . . . . . . . . . . . . . . . 6-5
Brake Hose Inspection . . . . . . . . . . . . . . . 6-5
Lining Inspection . . . . . . . . . . . . . . . . . . . 6-5
Brake Drum Inspection . . . . . . . . . . . . . . 6-5
Brake Rotor Inspection . . . . . . . . . . . . . . 6-6
Disc Brake Squeal or Squeak . . . . . . . . . . 6-6
Brake Caliper Noise . . . . . . . . . . .
. 6-6
Brake Pedal/Stoplight Adjustment . . . . .
6-6
Bleeding Brake Hydraulic System . . . . . . 6-7
Bleeding Hydro-Boost Brake System . . . 6-8
Power Brake Units . . . . . . . . . . . . . . . . . . 6-8
Parking Brake . . . . . . . . . . . . . . . . . . . . . . 6-8
Inspection
.
. . . . . . . . . . . . . . . . . . . . . . . 6-8
Drum Balance . . . . . . . . . . . . . . . . . . . . 6-9
Cable Adjustment . . . . . . . . . . . . . . . . . 6-9
Foot Pedal Type (G-Series) . . . . . . . . . . 6-9
Orcheln Lever Type (P-Series) . . . . . . . 6-9
Propeller Shaft Drum-Type Brake
Adjustment (Drum On) . . . . . . . . . . . . . 6-9
Parking Brake - Automatic . . . . . . . . . 6-10
Appendix 6-1 - Brake Caliper Noise . . . . . 6-13
Appendix 6-2 - Vacuum
Brake Bleeder . . . . . . . . . 6-15
Appendix 6-3 - Brake Lining
Life Expectancy . . . . . . . . 6-14
SECTION 7 - ENGINE . . . . . . . . . . . . . . . . . . 7-1
Principles of Increased Engine Life . . . . . . . 7-1
Gasoline Engine . . . . . . . . . . . . . . . . . . . . . . 7-2
Diesel Engine . . . . . . . . . . . . . . . . . . 7-2, 7-2A-B
Exhaust Manifolds . . . . . . . . . . . . . . . . . . . . 7-3
Table - 2
Service Tips . . . . . . . . . . . . . . . . . . . . . . . . . 7-3
Nodular Iron Manifold Shrinkage . . . . . . . 7-3
Cast Iron Manifold Cracking . . . . . . . . . . 7-3
Cast Iron Warping . . . . . . . . . . . . . . . . . . . 7-3
Exhaust Manifold and Plug Wire Failure . 7-4
Exhaust Manifold Leaks . . . . . . . . . . . . . 7-4
Left Exhaust Pipe to Engine
Oil Filter Interference . . . . . . . . . . . . . . . . 7-4
Engine Lubrication . . . . . . . . . . . . . . . . . . . . 7-6
General Description . . . . . . . . . . . . . . . . . 7-6
Oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
Quality . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
Viscosity . . . . . . . . . . . . . . . . . . . . . . . . 7-7
Temperature . . . . . . . . . . . . . . . . . . . . . 7-8
Energy Conserving Oils . . . . . . . . . . . . 7-8
Synthetic Engine Oils . . . . . . . . . . . . . . 7-8
Maintenance and Inspection . . . . . . . . . . 7-9
Checking Oil Level . . . . . . . . . . . . . . . . 7-9
Changing the Oil .. . . . . . . . . . . . . . . . . . 7-9
Changing the Oil Filter . . . . . . . . . . . . . 7-9
454 Engine Oil Fill Capacity . . . . . . . . . 7-9
Dipstick Replacement . . . . . . . . . . . . 7-10
Appendix 7-1 - Guideline For Engine Oil
Consumption . . . . . . . . . . 7-11
Engine Cooling System . . . . . . . . . . . . . . . 7-13
General Description . . . . . . . . . . . . . . . . 7-13
Thermostat . . . . . . . . . . . . . . . . . . . . . . . 7-13
Engine Cooling Fans . . . . . . . . . . . . . . . 7-14
Radiator/Heater and
Engine Deaeration System . . . . . . . . . . 7-16
Maintenance and Inspection . . . . . . . . . 7-17
Coolant Level . . . . . . . . . . . . . . . . . . . . . 7-17
Thermostat Check . . . . . . . . . . . . . . . . . 7-18
Flushing Cooling System . . . . . . . . . . . . 7-19
Appendix 7-2 - Radiator Additives . . . . . . 7-20
Appendix .7-3 - Engine Cooling
Instructions To
RV Manufacturers . . . . . . 7-21
Engine Fuels . . . . . . . . . . . . . . . . . . . . . . . . 7-22
Gasoline Engine . . . . . . . . . . . . . . . . . . . 7-22
Fuel Types . . . . . . . . . . . . . . . . . . . . . . 7-22
Diesel Engine . . . . . . . . . . . . . . . . . . . . . 7-23
Fuel Types . . . . . . . . . . . . . . . . . . . . . . 7-23
Appendix 7-4 - Use of Gasohol In
Gasoline Engines . . . . . . 7-24
Appendix 7-5 - Methanol/Gasoline
Blends Pose
Potential Problems . . . . . 7-25
Engine Fuel Systems . . . . . . . . . . . . . . . . . 7-29
Gasoline Engine . . . . . . . . . . . . . . . . . . . 7-29
System Description . . . . . . . . . . . . . . 7-29
Fuel Tank . . . . . . . . . . . . . . . . . . . . 7-29
Fuel Pump . . . . . . . . . . . . . . . . . . . . 7-29
Evaporative Control System . . . . . . 7-29
Fuel Filters . . . . . . . . . . . . . . . . . . . 7-30
Carburetor . . . . . . . . . . . . . . . . . . . . 7-31
Table - 3
TABLE OF CONTENTS (Cont'd)
Maintenance and Inspection . . . . . . . 7-31 Typical RV Isolator
TBI Fuel Injector -General . . . . . . . . 7-31 Failure Modes . . . . . . . . . . . . . . . . . 7-63
Closed and Open Loop . . . . . . . . . . . . 7-32 Charging System - 1987
Fuel Control Operation . . . . . . . . . . . . 7-32 to Current . . . . . . . . . . . . . . . . . . . . . . 7-64
TBI Injector . . . . . . . . . . . . . . . . . . . . . 7-33 . CS Series Generator and
TBI Pressure Regulator . . . . . . . . . . . 7-33 Isolator Diagnosis . . . . . . . . . . . . . . . 7-65
Idle Control . . . . . . . . . . . . . . . . . . . . . 7-34 Solid State Isolator . . . . . . . . . . . . . . . 7-65
Throttle Position Sensor (TPS) . . . . . . 7-34 Electromechanical Isolator . . . . . . . . 7-65
Fuel Pump Circuit . . . . . . . . . . . . . . . . 7-35 Maintenance and Inspection . . . . . . . 7-65
Fuel Line Filter . . . . . . . . . . . . . . . . . . 7-35 Ignition System . . . . . . . . . . . . . . . . . . . . 7-66
Fuel Tank . . . . . . . . . . . . . . . . . . . . . . 7-36 General Description . . . . . . . . . . . . . . 7-66
Evaporative Emission Control . . . . . . 7-36 H.E.I . Distributor . . . . . . . . . . . . . . . . . 7-66
Diesel Engine . . . . . . . . . . . . . . . . . . . . . 7-36 Secondary Wiring . . . . . . . . . . . . . . 7-67
System Description . . . . . . . . . . . . . . 7-36 Spark Plugs . . . . . . . . . . . . . . . . . . . 7-67
Maintenance and Inspection . . . . . . . 7-37 Ignition Timing . . . . . . . . . . . . . . . . 7-69
Water in Fuel . . . . . . . . . . . . . . . . . . 7-37 Maintenance and Inspection . . . . . . . 7-69
Primary Fuel Filter Water Drain . . . 7-37 H.E.I. Distributor . . . . . . . . . . . . . . . 7-69
Secondary Fuel Filter . . . . . . . . . . . 7-38 H.E.I. Test Procedure . . . . . . . . . . . 7-69
Appendix 7-6 - Plugged Fuel Return General Test . . . . . . . . . . . . . . . . 7-69
Line and Engine Module Test . . . . . . . . . . . . . . . . 7-70
Performance . . . . . . . . . . 7-39 Checking H.E.I . System
Appendix 7-7 - Vapor Lock Cause Connections . . . . . . . . . . . . . . . . . . 7-70
and Cure . . . . . . . . . . . . . . 7-40 Spark Plug Wires . . . . . . . . . . . . . . 7-70
Appendix 7-8 - Troubleshooting Aftermarket Spark Plugs/Plug Puller . . . . . . . . . 7-71
Fuel Systems . . . . . . . .. . . 7-50 6.2L Diesel Glow Plug
Appendix 7-9 - Secondary Electrical System . . . . . . . . . . . . . . . . . . 7-71
Fuel Systems . . . . . . . . . . 7-52 General Description . . . . . . . . . . . . . . 7-71
Engine Electrical System . . . . . . . . . . . . . . 7-55 System Components . . . . . . . . . . . 7-71 .
Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-55 Maintenance and Inspection . . . . . . . 7-74
General Description . . . . . . . . . . . . . . 7-55 Glow Plug Test . . . . . . . . . . . . . . . . 7-74
Ratings . . . . . . . . . . . . . . . . . . . . . . . . 7-55 Appendix 7-10 - Battery Size
Maintenance and Inspection . . . . . . . 7-55 and Cranking vs.
Visual Inspection . . . . . . . . . . . . . . 7-56 Temperature . . . . . . . . . 7-75
Built-In Hydrometer Appendix 7-11 -Add-On (Auxiliary)
(Delco Sealed-Top Battery) . . . . . . . 7-56 Electrical Equipment
Electrical Load Test Installations . . . . . . . . . . 7-79
(Delco Sealed-Top Battery) . . . . . . . 7-57 Appendix 7-12 - "Hot Start" Problem
Jump Starting -With Conditions . . . . . . . . . . . 7-80
Auxiliary (Booster) Battery . . . . . . . 7-57 Appendix 7-13 -Starter Motor
Multi-Battery Electronic Engagement After
Jump Starting Aid . . . . . . . . . . . . . . 7-58 Initial Start-Up . . . . . . . . 7-83
Battery Removal Appendix 7-14 -Generator Belt Usage on
and Replacement . . . . . . . . . . . . . . 7-59 6.2L Diesel Engines . . . . 7-84
Starting (Cranking) System . . . . . . . . . . 7-59 Appendix 7-15 - Torsional Isolator . . . . . . 7-85
General Description . . . . . . . . . . . . . . 7-60 Appendix 7-16 - Electronic
Maintenance and Inspection . . . . . . . 7-61 Cruise Control . . . . . . . . 7-86
Starting Problems Engine Emission Controls . . . . . . . . . . . . . 7-92
(High Ambient Temperatures) . . . . 7-61 Vehicle Emission Control Information
Starting Problems Label . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-92
(Poor Ground) . . . . . . . . . . . . . . . . . 7-61 Emission Controls - Systems and
Charging System . . . . . . . . . . . . . . . . . . 7-62 Components . . . . . . . . . . . . . . . . . . . . . . 7-92
'General Description . . . . . . . . . . . . . . 7-62 General Description . . . . . . . . . . . . . . 7-92
Generator Sizing and Selection . . . . . 7-62 Positive Crankcase Ventilation (PCV)
Battery Isolator . . . . . . . . . . . . . . . . . . 7-62 System -Gasoline Engine . . . . . . 7-92
Typical RV Isolator Crankcase Ventilation - Diesel
Voltmeter Checks . . . . . . . . . . . . . . 7-63 Engine . . . . . . . . . . . . . . . . . . . . . . . 7-93
TABLE OF CONTENTS (Cont'd)
Early Fuel Evaporation (EFE)
System - Gasoline Engine . . . . . . 7-93
Thermostatic Air Cleaner (Thermac)
- Gasoline Engine . . . . . . . . . . . . . 7-93
Evaporative Emission Control System
(EECS) . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-94
General Description . . . . . . . . . . . . . . 7-94
Fuel Vapor Canister -Primary . . . 7-95
Fuel Vapor Canister - Auxiliary . . 7-96
Maintenance and Inspection . . . . . . . . . 7-97
Positive Crankcase Ventilation (PCV)
- Gasoline Engine . . . . . . . . . . . . . . . . . 7-97
Checking the PCV System . . . . . . . . . 7-97
Early Fuel Evaporation (EFE) . . . . . . . . . 7-97
Inspection . . . . . . . . . . . . . . . . . . . . . . 7-97
Checking EFE System . . . . . . . . . . . . 7-97
Air Injection Reactor (A.I .R.) System
- Gasoline Engine . . . . . . . . . . . . . . . . . 7-97
Inspection . . . . . . . . . . . . . . . . . . . . . . 7-98
Air Pump Drive Belt Adjustment
and Replacement . . . . . . . . . . . . . . . . 7-99
Check Valve Inspection . . . . . . . . . . . . . 7-99
Thermostatic Air Cleaner . . . . . . . . . . . . 7-99
Checking Thermac Air Cleaner . . . . . 7-99
Thermometer Check of Sensor . . . . . 7-99
Air Cleaner Element and PCV Filter
Replacement . . . . . . . . . . . . . . . . . . . . 7-99
Appendix 7-17 - H5D Emission
System . . . . . . . . . . . . . 7-101
SECTION 8-TRANSMISSION . . . . . . . . . . 8-1
General Description . . . . . . . . . . . . . . . . . 8-1
Models 350C and 400-475 Series . . . . . 8-1
Torque Converter Clutch . . . . . . . . . . . 8-2
Controls . . . . . . . . . . . . . . . . . . . . . . . . 8-2
Manual Linkage . . . . . . . . . . . . . . . . . . 8-2
Vacuum Modulator System . . . . . . . . . 8-2
Downshift (Detent) Cable System
- 350C Transmission - G-Series . . . 8-2
Detent Downshift Electrical Circuit
- 400-475 Series Transmission . . . . . . . . 8-2
Maintenance and Inspection . . . . . . . . . . . . 8-3
Fluid Level and Appearance . . . . . . . . . . 8-3
Capacity . . . . . . . . . . . . . . . . . . . . . . . . 8-3
Checking and Adding Fluid . . . . . . . . . 8-4
Changing Fluid . . . . . . . . . . . . . . . . . . . 8-4
Automatic Transmission
Manual Linkage . . . . . . . . . . . . . . . . . . . . 8-5
Cooler Lines . . . . . . . . . . . . . . . . . . . . . . . 8-5
Transmission Mount . . . . . . . . . . . . . . . . 8-5
Transmission Shifting . . . . . . . . . . . . . . . 8-5
Engine/Transmission Torque
Converter/Clutch Balancing . . . . . . . . . . . 8-6
Overdrive Transmission 4L80E . . . . 8-6
Appendix 8-1 - Transmission Fluids and
Cooler Tips . . . . . . . . . . . . . 8-7
Appendix 8-2 -Temperature Monitors . . . 8-10
Appendix 8-3 = Geared Road Speed
Determination . . . . . . . . . 8-11
Appendix 8-4 - Checking Gear Ratios
. - Single Drive Axles . . . . 8-12
APPENDIXES . . . . . . . . . . . . . . . . . . . . . . . . A-1
Appendix A - Drive Belts and Tension
Specifications . . . . . . . . . . . A-1
Appendix B - Preparing the Motor Home
for Storage . . . . . . . . . . . . . . A-5
Appendix C - Nut and Bolt
Identification . . . . . . . . . . . . A-7
Appendix D - Weight Distribution and
Helpful Conversions . . . . . A-15
INDEX
WARRANTY
SERVICE BULLETINS
SECTION 1 -INTRODUCTION
GENERAL INFORMATION
Chevrolet chassis are available in two series for motor home use. These are the G-Series and the P-Series .
G-SERIES MOTOR HOME CHASSIS
The G-Series, or cutaway van, as it is commonly referred to before the addition of the motor home body, is a chassis which includes a full floor, frame, front cab (less back)and engine as shown in Figure 1-1 . Many . of the components including the front-end sheet metal, instrumentation,
driving controls and seats are common with the Chevrolet Van .
Figure 1-1 -G-Series Motor Home Chassis
P-SERIES MOTOR HOME CHASSIS
The P-Series motor home chassis is an engine and frame unit which includes the driving controls, as shown in Figure 1-2 . The P-Series (P30 is the series and size class used for motor homes) is available in five wheelbase lengths .
These are:
*Start-up production 1988 model- year
**Start-up production 1991 model year
Figure 1-2- P-Series Motor Home Chassis
IDENTIFICATION NUMBERS
There are several numbers that are important in identifying the vehicle and components used on the vehicle .
They are the Vehicle Identification Number (VIN) and the Service Parts Identification Label - Figure 1-4
Model Number Wheelbase Length
(inches)
CP 3112 137
CP 31432 - 52 158.5
CP 31832 - 52 178
CP 31932 - 52 190*"
CP 32032 - 52 208*
P30 HD CUTAWAY AS A
MOTOR HOME
" Outstanding strength and durability if Class A chassis: best-in-class GVWRs from 10,500 lbs. up to 14,500 lbs .
SECTION 1 - INTRODUCTION
P30 HD CUTAWAY
MOTOR NOME
Ease of upfitting on full frame with industry standard straight frame rails.
Choice of four wheeelbases: 158.5-, 178-, 190-, and 208- inches.
Can accommodate bodies of 22-, 24-, 26- and up to 27- feet in length .
7.4 liter (454 cubic inch) fuel-injected V8 gasoline engine with 230 horse-power and 380 lbs.-ft. of torque.
Improvements to the 7.4-liter (454) V8 gasoline engine include revised inlet manifold, new hydrodynamic front crank seal and much more.
Smooth-riding independent front suspension to step over bumps plus tapered leaf springs to enhance vehicle stability .
One-piece fiberglass hood with grab handles that tilts forward for easy access to engine and other under-the hood components.
Fiberglass cab-entry steps for lifetime protection against corrosion .
B-pillar grab handles for easy access to cab.
1-1A
Comfortable, roomy cab with standard adjustable highback front bucket driver's seat.
Ample use of glass for commanding view of the road.
4-speed automatic transmission (41-80-E) with overdrive electronically controlled for smooth shifting,powerful torque multiplication and economical highway operation.
4-wheel disc brakes for smooth, powerful braking (std. on 14,500 lbs. GVWR models).
Solor-RayTm light tinted glass reduces interior vehicle temperature in cab area for greater driver/passenger comfort.
Dual rear wheels provide outstanding stability and enhanced ride smoothness.
" Up to 5,000-Ib ..capacity on front axle; up to 10,000-Ib.
capacity on full-floating rear axle.
STANDARD INTERIOR CONTENT
Air conditioning : front
Armrest: left hand padded
Cigarette lighter : included on instrument panel
Dome lamps: with front-door activated switches
Floor coverings: embossed black rubber mat on front floor area and wheelhousings
Gages: speedometer, odometer, trip odometer, fuel level, voltmeter, oil pressure, engine temperature and additional tell-tale lights
Headliner: hardboard
Heater: deluxe outside air heater and defogger Insulation : in cab area
Parcel Tray: on top surface of instrument panel extension:includes beverage holder provisions
Radio: electronically-tuned AM radio with digital clock and fixed mast antenna
Seats: adjustable high-back front bucket driver's seat with all-vinyl trim
Steering Wheel: 2-spoke, with anti-theft feature on steering column
Stowage Box: with latched door on front face of instrument panel extension
Sunshades: padded, color-keyed RH and LH sunshades Windshield Wipers: intermittent wiper system
STANDARD EXTERIOR CONTENT
Bumpers: chrome front
Headlamps: quad rectangular halogen
Horn: electric dual high-note and low-note
Tires: six LT215/85FI16C steel belted radials (158.5 inch wheelbase)
six 7.50/16LT/D nylon ply blackwalls (178 inch wheelbase)
six 8.0013/19.5/D steel belted radial blackwalls (190 and 208 inch wheelbases)
Undercoating : on step panels and front wheelhousings
Wheels: six painted steel
Windows: light tinted Solor-RaVrl glass on all windows
SECTION 1 -
VEHICLE IDENTIFICATION NUMBER (VIN)
The VIN is the legal identification of the vehicle. It appears on a plate which is attached to the top left of the instrument panel on the G-Series chassis and can be easily seen through the windshield from outside the
vehicle (Figure 1-3). On the P-Series chassis the VIN is attached to the front of the dash and toe panel to the left of the steering column. (See Figure 1-2) for pre 1990. .Currently the VIN plate is located center and on
top of the radiator support. The VIN also appears on the Vehicle Certificates of Title and Registration . Refer to Figure 1-4 to determine the vehicle manufacturer,model and chassis type, engine type, GVW range,
model year, plant code and production sequence number.
Figure 1-4- Vehicle Identification Number Codes
INTRODUCTION
Figure 1-3- Vehicle Identification Number (VIN)
Nation of Origin
1 = U .S . Built
2 = Canadian Built
3 = Mexican Built
Code Make
A Chevrolet Bus'
B Chevrolet Incomplete
C Chevrolet Truck
D GMC Incomplete
E Cadillac Incomplete
H GM of Canada Bus
T GMC Truck
IGJ GMC Van/Bus
IGK GMC MPV
IGN Chevrolet MPV
'Van with 4th Seal
GVWR/BRAKE SYSTEM
Code GVWR Range
B 3001-4000
C 4001-5000
D 5001-6000
E 6001-7000
F 7001-8000
G' 8001-9000
H 9001-10,000
J 10,001-14,000
K 14,001-16,000
' Includes G-Van Bus
Brake System
Hydraulic
Hydraulic
Hydraulic
Hydraulic
Hydraulic
Hydraulic
Hydraulic
Hydraulic
Hydraulic
G 3
Code Body Type
0 Pickup/Panel Delivery
1 Hi-Cube/Cutaway Van
2 Forward Control
3 Four-Door Cab
4 Two-Door Cab
5 Van
6 Suburban
7 Motor Home Chassis
8 Utility (Jimmy/Blazer)
9 Stake
Line and Chassis Type Chassis 1
Production Sequence Number
1 2 4 9 9
Engine Type and Make
Code Producer Type RPO
C DDAD 6 .2L V8 Diesel LH6
E Pontiac 2 .5L L4 TBI LN8
F Powertrain 6 .5L V8 Diesel L65
H Chevrolet 5 .OL V8 TBI L03
J DDAD 6 .2L V8 Diesel LL4
K Chevrolet 5 .7L V8 TBI LOS
M Chevrolet 5 .71 V8 4BBL LT9
N Chevrolet 7 .4L V8 TBI L19
R Chevrolet 2 .BL V6 TBI LL2
W Chevrolet 7 .4L VB 4BBL LE8
Z Chevrolet 4 .3L V6 TBI LB4
Code Year
A - 1980 Assembly Plant
B -1981 B Baltimore, MD
C -1982 F Flint, MI
D -1983 J Janesville, WI
E -1984 S St . Louis, MO
F -1985 E Pontiac East, MI
G -1986 V Pontiac, MI
FI -1987 Z Fort Wayne, IN
J -1988 1 Oshawa, ON
K -1989 2 Moraine, OH
L -1990 3 Detroit, MI
M -1991 4 Scarborough, ON
N -1992 7 Lordstown, OH
8 Shreveport, LA
0 Pontiac, MI I Code Line Type
R Conventional Cab 4 x 2
D Military Truck 4 x 4
V Conventional Cab 4 x 4
G Van 4 x 2
P Forward Control 4 x 2
S Sm Conventional Cab 4 x 2
T Sm Conventional Cab 4 x 4
M Sm Van 4 x 2
SECTION 1
SERVICE PARTS IDENTIFICATION
LABEL
The Service Parts Identification Label (Figure 1-5) is provided on both G- and P-Series vehicles. On the G-Series vehicle, the label is located on an inner hood panel surface.
On the P-Series vehicle, the label is located on an inner body panel by the body builder .
The label lists the vehicle identification number, wheelbase, and all production options or special equipment on the chassis when it was shipped from the factory including paint information. ALWAYS REFER TO THIS INFORMATION
WHEN ORDERING PARTS .
MOTOR HOME TOWING
The term. "GCWR" is a new term to be learned when the motor home operator decides to enter the "world of towing
." The term GCWR refers to the Gross Combination
Weight Rating which includes the combined weight of the motor home (or truck) with all of its contents and the total weight of the trailer, car, boat or whatever is being towed.
Mini- and full-size motor homes do not have specific charts that cover trailer towing requirements . The chart shown in Figure 1-6 has been taken from the Chevrolet Trailer Guide and is presented as an aid to the motor home owner to assure reasonable performance without placing undue stress on the driveline components. The chart covers all engine and axle combinations used within General
INTRODUCTION
'Motor Home Chassis only 'Available only when RPO KC4 Engine Oil Cooler is specified.
THIS CHART SHOWS THE MAXIMUM ALLOWABLE GROSS COMBINATION WEIGHT RATING (GCWR) BASED ON ALL OF THE AVAILABLE TRUCK ENGINES AND REAR AXLE RATIOS WITH AUTOMATIC TRANSMISSIONS . THE GCWR INCLUDES THE TOTAL LOADED WEIGHT OF BOTH THE TRUCK AND TRAILER . ANY AVAILABLE ENGINE MAY BE USED FOR TRAILERING IF THE GCWR SHOWN IS NOT EXCEEDED .
NOTE : THE TRAILER WEIGHT CAN BE INCREASED BY 25% IF THE VEHICLE SPEED WILL NOT EXCEED 25 MPH .
Figure 1-6- Gross Combination Weight Rating Chart
NOTE: GCWR for unit with 4L80E transmission is 20,000# with 4:63 or 5:13 ratio.
Service Parts Identification^~~~ '' DO NOT REMOVE
1G?KP37WXK3300831 178 .0 CP31532
C7S DET D1Yr ENV E5Z EOC E?Z G61 HF7 JF9 K68 LE°_ MX1
M40 NA9 N32 NN4 RoE SLM VJ9 V73 XSN Y36 Y97 Y38 YP5
YSN ZW9 Z5P 01L OIU 5Y9
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxlcxx
ORDER NO 582JJJ
Figure 1-5-Service Parts Identification Label
Motors, however all combinations are not available in the motor home product . Additional information may be available from the various motor home manufacturers as well as the current Chevrolet Trailer Guide. Examine the rating for your motor home provided by the RV manufacturer.
Refer to pages 5-3, 6-14, 7-1 and 8-7 for additional charts and information relating to work/stress and vehicle component life expectancy.
CAUTION: TO HELP AVOID PERSONAL INJURY DUE TO POOR BRAKING ACTION, ADEQUATE SIZE TRAILER BRAKES ARE REQUIRED ON TRAILERS OVER 1000 POUNDS OF LOADED WEIGHT.
GROSS COMBINATION WEIGHT RATING (GCWR) Includes Weight of Both Truck and Trailer
By Engine & Axle Ratio For Recreational Applications
GCWR (lb .) 6000 M00 7000 7500 6000 6500 9000 9500 10,000 10,500 1t= 11,500 12,000 12,500 13,500 14,000 14,500 15,000 16,000 19,000
ENGINES REAR AXLE RATIOS
2 .5L 1151) 4 GAS 3.73 4.10/4.11
2 .6L 073) V6 GAS 3 .42 3 .73/4.11 3 .731
43L 1252) V6 GAS 2 .41 2 .56 2 .73 3 .08 3.42 3 .73 4 .11
SJII (305) V6 GAS 2 .41 2 .56 2 .73 3.08 3 .42 3.73
5 .71. J350) V6 GAS 2 .73 3 .08 3 .23 3 .42 _3.7_3 4 .10 4 .56
62L V6 DIESEL 2 .73 3 .08 3.23 3 .42 3 .73 4.10 4 .56 5.13`
7 .41. 14M) VB GAS 3.21 3 .42 3 .73 4 .10 4.5N4.88'
By C. JAY HAYNOR, F15585
Technical Editor
"Why?" ?
SECTION 1 INTRODUCTION
ABOUT RV WEIGHTS
A discussion of recreational vehicle weight ratings, how they are determined, and how exceeding these figures can affect the operation of the vehicle.
Recently, Paul, a friend of mine who owns a large auto parts warehouse, was talking with me about one of his delivery trucks. The truck was a 1986 model with a gross vehicle weight rating (GVWR) of 11,000 pounds. This same
chassis is used by motorhome manufacturers to build Class C coaches. The truck gave excellent service for eight months. Not too long after that, however, all of the driveshaft universal joints wore out, and multiple disc brake pad and rear brake shoe replacements were necessary. These and other repairs were causing Paul some concern . He noted that the fronttires were cupped severely, and the rear tires had sidewall cracks. Paul's question to me . was, When I talked with a few of the employees, they confirmed
my suspicions. It seems that one of the salesmen was selling to a new account and used this truck to deliversome of the "parts ." The "parts" included pallets of oil, transmission fluid, and batteries . The truck was overloaded and, equally important, subjected to poor weight distribution.
The load on the rear was excessive, thereby cracking the sidewalls on the rear tires. The excessive rear load also lowered the rear of the truck, thereby raising the front.
Because of that, the front tires made less contact with the road, and cupping resulted . This reminded me of pictures I once saw of a Federal Express airplane that was so heavily loaded in the rear that the front of the plane actually lifted well off the ground. The truck instance, though not as dramatic, was an example of the same type of overload condition . And many of the other mechanical difficulties that the truck began to experience could be attributed to overloading .
The major components of a chassis- including the engine, transmission, brakes, axles, tires, and frame - are designed to accommodate a particular weight, and if these components are overloaded, their life expectancy diminishes rapidly.
In the "good ole days" weight ratings were more guidelines than rigid "to the ounce" specifications . Then, along came the energy crunches of the 1970s. As a result, fuel economy and production costs became critical . Automobile manufacturers and RV manufacturers found that one of the
fastest and easiest ways to increase fuel economy and to reduce production costs was to lighten the vehicles wherever they safely could . Today, more than ever before, it is of the utmost importance that we pay more attention to technical definitions and weights as they relate to our homes on wheels.
One of the organizations involved in establishing definitions that motorhome manufacturers and chassis builders use is the Recreation Vehicle Industry Association (RVIA).
The weight issue is equally important to consumers . So, let's consider some ofthe definitions that we coach owners should understand before taking the next step, which is actually weighing our motorhomes.
Two definitions exist for the term chassis as it applies to motorhomes. In the case of a Class A motorhome, the chassis consists of the frame, running gear, steering, and suspension system. In the case of a Class C or micro-minimotorhome, the chassis includes the same components as does a Class A motorhome chassis plus a cab.
From the definitions above, we can clearly see that the chassis is, separate from the body or coach in a Class A motorhome and separate from the motorhome body in a Class C coach . It is the chassis manufacturer that determines the weight ratings and load specifications . The only exception would be if the chassis were modified and recertified by the company performing the modification . This would be indicated on a label positioned near the original label on the coach. The location of these labels varies from vehicle to vehicle .
Gross vehicle weight rating (GVWR) is the weight specified by the chassis manufacturer as the maximum loaded weight of the vehicle (including driver and passengers).
Sometimes a tag axle -a non-powered rear axle- is added to a chassis. This usually is done to increase the GVWR of the chassis, and, as previously mentioned, it becomes the responsibility of that party to post and certify the new GVWR.
Gross axle weight rating (GAWK) is specified by the chassis manufacturer as the load carrying capacity of a single-axle system as measured at the tire-ground interface (in other words, at the place where the tire meets the
ground). It is important to note that the GAWK is limited to the lowest individual rating of the tires, the wheels, the springs, or the axle - in other words, whichever component is the weakest link in the chain. Therefore, changing from load range D to load range E or F tires may or may not increase the GAWK, since this rating could be dependent upon other (weaker) components. The GAWK assumes that the weight is evenly distributed over the axle, with 50 percent on the right side and 50 percent on the left side - not 70/30, for instance. In other words, in the case of an axle with a GAWK of 6,000 pounds, the load distribution .
should be 3,000 pounds on one side and 3,000 pounds on the other.
SECTION 1
Axle weight is both the amount of weight carried by a
single axle and the amount of weight transmitted to the
highway by one axle.
Shipping weight is the average weight of a specific
vehicle as it leaves the assembly plant, including grease
and oil plus regular production options but without any primary
mover engine fuel (gasoline or diesel fuel) .
Empty weight is defined as the shipping weight of a specific
vehicle plus the maximum weight of primary mover
engine fuel (gasoline or diesel fuel).
Curb weight is the weight of the vehicle empty (without
payload and driver) but including engine fuel, coolant,
engine oil, tools, spare tire, and all other standard equipment.
It is determined without water in the tanks or water
heater and with empty LP-gas containers. (Note: This
definition, while accepted within the RV industry, may
differ from definitions utilized by governmental regulatory
agencies.)
Wet weight is the empty weight of a specific vehicle with
the fresh water tanks, water heater, and LP-gas containers
full but with waste water holding tanks empty. This weight
is particularly significant to motorhome owners, because
when you subtract this figure from the gross vehicle weight
rating, you have a fairly accurate indication of the amount
of weight that can be added to the vehicle, including driver
and passengers, clothing, foodstuffs, etc .
Payload is a term commonly used in the trucking industry.
In the RV industry, the term carrying capacity also is used.
Carrying capacity is defined as the average weightthat can
be added to a specific vehicle without exceeding the
GVWR. Carrying capacity can be computed by subtracting
the empty weightof the vehicle from the GVWR figure . The
addition of any other equipment or cargo and passengers
adds to the vehicle weight and subtracts from the allowable
carrying capacity. It is important to rememberthat the limiting
factor in this rating could be the axles, springs, tires,
transmission parking pawl, or any other equipment.
Center of gravity is the point where the weight of the
chassis and/or body and payload is concentrated and, if
suspended at that point, would balance front-to-rear and
side-to-side. Cornering, acceleration, and other forces are
considered as acting on a vehicle's center of gravity. Thus,
it has a great influence on body lean and other handling
characteristics . Even if all of the weights fall within the
specifications, if they are not distributed properly, the coach
could still suffer from excessive body lean or substandard
handling characteristics. It should be noted that the center
of gravity of a basement model coach will be higher than
that of a traditionally designed motorhome .
Weight distribution is the arrangement of body and payload
weight on a vehicle's chassis. It has a very definite
bearing on the life of the tires, axles, springs, frame, and
other parts. Thefactthat the total weightof the vehicle does
not exceed the recommended maximum GVWR does not
insure that the coach is not overloaded. Overloading can
INTRODUCTION
be due to improperly positioning heavy materials so that
the load is centered over one rear tire or so far forward on
the body that the front axle and tires are overloaded. An
understanding of the proper methods of load placement
will enable coach owners to prevent an overload condition .
It should be noted also that the limiting factor is the weight
rating, not the cubic foot capacity of the storage compartments.
Some motorhome owners may be under the
impression that if the manufacturer has provided the
space, it must be acceptable for them to fill each nook and
cranny to capacity . This isn't always the case, however. By
providing varied and ample storage space, motor coach
manufacturers are attempting to meet a multitude of
needs.
Weighing your coach . Of course, the only way to be sure
to avoid an overload condition is to weigh the coach. To do
so accurately, the coach owner needs to find a scale that
has a level area on the side, and to develop an excellent
rapport with the person doing the weighing. The level side
area is very important, because it will be necessary to have
50 percent of the left and right sides of the coach off the
scale during some of the weighing. If the side area is not
level, the side weights will be incorrect . Suitable scales
might be found at truck stops, sand and gravel pit operations,
and moving companies.
I would suggest that you make a photocopy of the coach
weighing worksheet that accompanies this article and use
it as a reference at the scale. Weigh the coach at an off
time, since the entire process can take up to one-half hour.
Before weighing the coach, load it as you normally would
for travel, including food, clothing, fuel, water, propane, etc .
This is not the time to be conservative!
The worksheet divides the coach into four sections. This is
done by finding the halfway point between the front and
rear tires (axles) and the halfway point between the front
tires and then the halfway point between the rear tires. Do
not simply use the distance between the front and rear of
the coach body; be sure to use the axles as a reference
point. Use tape to mark the side-to-side halfway points on
the front bumper and on the rear bumperto make the reference
points easily visible. Do the same for the front-to-rear
halfway points by applying tape to the side of the coach.
Dirve the coach onto the scale to the point that the front-torear
tape pieces indicate that one-half of the wheelbase is
on the scale and one-half is off. Referring to the worksheet,
this will be weight number W1 .
Weigh the tow car as you normally tow
it, and if you find that it is overloaded,
remove any weight necessary to bring
it into specifications.
Next drive the entire motorhome onto the scale. This will be
weight number W2. Then drive off the scale so thatthe side
SECTION 1
tape stripe indicates that the rear half of the chassis
remains on . This will be weight W3. I emphasize that it is
important that one-half of the chassis, not the coach, rests
on the scale during weighing .
Weight number W1 should, not exceed the GAWK for the
front axle. Weight number W2 should not exceed the total
GVWR. Weight number W3 should not exceed the rear
axle GAWR .
Now comes the time when rapport with the scale attendant
and patience come in handy. To make these weights more
meaningful, use the side-to-side and front-to-rear tape
pieces to divide the chassis up into quarters and then weigh
each section : front left, weight zone W4; rear left, weight
zone W6; front right, weight zone W5; and finally rear right,
weight zone W7. The weights for zone W4 and zone W5
should be about equal, as should the weights for zones W6
and W7. If this is not the case, try to move items inside the
coach to bring the weights close.
When you compare the total weight of the two front quarters
to the total axle weight, the figures probably will not be
exactly equal, but they should be close. The same applies
to the rear axle . It is also possible that the front and rear
GAWR when totaled will be more than the GVWR. This is
because the limiting factor may be something such as the
transmission parking pawl, braking capacity, or another
component .
Since tire manufacturers determine pressure recommendations
for each individual tire based on the weight that a
particular tire is carrying, these quartered weights are very
INTRODUCTION
important. Use the front and rear axle weights on the worksheet
to determine the proper air pressure by consulting
the tire manufacturer's tire manual, which should be available
at any tire store.
One last word of caution : start with the weight you would
normally carry when traveling . If the weight places the
vehicle over the GVWR, remove some weight and weigh
the coach again. The importance of weight and weight distribution
in terms of safety and your motorhome's overall
health cannot be overemphasized .
Another term with which motorhome owners should be
familiar is gross combination weight rating (GCWR),
which is the value specified by the chassis manufacturer as
the maximum allowable total loaded weight of the tow
vehicle and trailer combination . For our purposes the tow
vehicle is the motorhome, and the trailer ordinarily is a
towed car. To determine what size car can be towed safely
behind a motorhome, subtract the actual motorhome
weight, which must be less than the GVWR, from the
GCWR. Normally this weight will be approximately 3,000
pounds, in which case the towed car combination (including
trailer, dolly, or tow bar) should not exceed 3,000
pounds. Weigh the towcar as you normally tow it, and if you
find that it is overloaded, remove any weight necessary to
bring it into specifications .
I hope this short discussion of motorhome weights will
motivate youto weigh your coach and make any necessary
adjustments. And if you're looking for a new coach, it is
hoped that this article will be another factor in your
selection .
Various components of the motor home chassis must
have the proper lubrication to operate as designed. This
lubrication must be done in accordance with the intervals
specified in the appropriate Maintenance Schedule for the
vehicle .
SECTION 1 -INTRODUCTION
LUBRICATION
RECOMMENDED FLUIDS AND LUBRICANTS
Following are charts which list the recommended fluids
and lubricants, component fluid capacities and lubrication
points .
Figure 1-7 = Recommended Fluids and Lubricants
USAGE FLUID/LUBRICANT
Power steering system and pump reservoir Power steering fluid, GM Part No. 1050017 or
equivalent
Manual steering gear Lubricant, GM Part No. 1052182 or equivalent
Differential - Standard or Locking Spiral Bevel
Axel Gearing . Pinion enters ring gear at centerline
SAE-80W GL-5 or SAE-80W-90 GL-5 gear lubricant
(SAE-80W - GL-5 in Canada) Do not use additive
with Eaton locking differential
Differential - Rockwell model C-103-12 1/4",
Commercial P model, Hypod gearing. Pinion enters
ring gear below centerline.
SAE-85W-140 GL-5 above 10 °F
SAE-80W-90 GL-5 below 15°F
Military spec 2105C
Brake system and master cylinder Delco Supreme 11 fluid or DOT-3 1052535
Propeller shaft slip spline and U joints Chassis Grease, GM Part No. 1052497 or equivalent
Hood Latch Assembly
a. Pivots and spring anchor
b. Release pawl
a. Engine Oil
b. Chassis Grease
Hood and Door Hinges Engine Oil
Automatic Transmission Shift Linkage Engine Oil
Chassis Lubrication Chassis Grease, GM Part No. 1052497 or equivalent
Engine Oil (Gasoline) "SG" or "SG/CC" or "SG/CD" Engine Oil
Engine Oil (Diesel) "CE/SG" Engine Oil
Automatic Transmission DEXRON IIE Auto. Trans. Fluid, GM Part No. 12345881
Parking Brake Cables Chassis Grease, GM Part No. 1052497 or
equivalent
Front Wheel Bearings Wheel bearing lubricant, GM Part No. 1051344 (One
Pound) or Exxon Ronex MP Grease or equivalent
Body door hinge pins, tailgate hinge and linkage,
folding seat, fuel door. hinge
Engine Oil
Windshield Washer Solvent GM Optikleen washer solvent, GM Part No. 1051515
or equivalent
Engine Coolant
GM 1825M Specifications
Mixture of water and high quality Ethylene Glycol
base type antifreeze, GM Part No. 1052753 or
equivalent
Key Lock Cylinder Lockeze or GM Part No. 12345120
SECTION 1
LUBRICANT CAPACITIES
INTRODUCTION
Figure 1-8-Lubricant Capacities
NOTE: With any side fill gear case, regardless of specification,
fill the case until fluid runs back out the
fill hole (Figure 1-9). DO NOT CONSIDER THE
FILL ADEQUATE JUST BECAUSE YOU CAN
REACH IT WITH YOUR FINGER.
Figure 1-9-Side Fill Gear Case Capacity
USAGE U .S. MEASURE
Differential
10-1/2 In. Ring Gear (Chevrolet) 6-1/2 pts .
10-1/2 In. Ring Gear (Dana 70) 7.2 pts .
9-3/4 In . Ring Gear (Dana) 6.0 pts .
10.5 In. Ring Gear (Saginaw 70) 7.0 pts.
11 .3 In. Ring Gear (Dana 80) 7.5 pts .
Engine Crankcase
Code 5.7L V8 - Drain & Refill 4 qts .
F-H
LM-P
- w/Filter Change 5 qts .
Code 7.4L V-8 - Drain & Refill 6 qts .
W - w/Filter Change 7 qts .
Code
C-F-J 6 .2L-6 .5 V-8 Diesel Including Filter 7 qts .
Transmission Automatic
350C - Total 10 qts .
- Refill 3 qts .
475 - Total 11 qts .
- Refill 3.5 qts .
4L80E - Total 13.5 qts.
- Refill 7.7 qts.
LUBRICATION POINTS
SECTION 1
Figure 1-10-Lubrication Points- G-Series
INTRODUCTION
*On some models, universal joints are sealed with no provision for lubrication. On models which have
lubrication provisions, use high-temperature lubricant (GM Part No. 1051344 or equivalent) .
Figure 1-11- Lubrication Points- P-Series
OLower Control Arms O5 Tie Rod Ends Transmission - Automatic
Upper Control Arms © Wheel Bearings 11 Carburetor Linkage - V-8
3~Upper and Lower Control 07 Steering Gear Brake Pedal Spring
Arm Ball Joints ®Air Cleaner - Element Universal Joints*
®Intermediate steering Shaft (PA10) O9 Master Cylinder ® Rear Axle
1~Control Arm Bushings and Ball Joints @Trans. Control Shaft ® Rear Axle
@Tie Rod Ends ©Air Cleaner - Element ~9 Oil Filter
@Wheel Bearings O7 Transmission - Automatic OO Brake Master Cylinder
®Steering Gear Clutch Cross-Shaft 11 Parking Brake Linkage
SECTION 1 -INTRODUCTION
NOTE: TYPICALLY THERE ARE EIGHT LUBRICATION
FITTINGS ON THE I -BEAM AXLE .
Figure 1-12- Lubrication Points-- P-Series with I -Beam Axle (Option No. FS3)
NOTE: See #13 Figure 1-11 . Grease must exit from all 4 bearings when lubricating U joints . Also grease spline on 2 and
3 shaft units . Grease must exit from spline plug.
ADEQUATE TEMPERATURE MODULATION
FROM DASH HEATER SYSTEMS
Over the past few months, I've received a number of letters on the subject of inadequate temperature modulation from dash heater systems. When one moves the temperature control lever to any position between the cold
and warm extremes, one expects modulated air. In some instances, however, that's not what one receives. The air is either too hot or too cold, and no temperature modulation is taking place. With the winter months almost upon us, it would seem that a brief discussion and modification suggestion is in order.
Two different systems are used for modulating air temperature in engine-operated dash heating systems. One is excellent and the other is not so good. The excellent one is the blend air door control system. This system incorporates an air control door at the end of the temperature control lever. The door is controlled via the dash lever, which is connected to the door by a cable. To regulate the outlet temperature of the air, this cable moves the door to determine what percentage of incoming air will go through the heater core, which remains fully hot .
The other system controls the outlet air temperature by controlling the flow of hot water through the heater core . All air is directed through the heater core. The other end of the temperature control cable is attached to a manual control lever in a water valve located in the heater hose that leads to the heater core.
Therein lies the problem - attempting to control the water temperature on the heater core .
As one moves the temperature control lever on the dash, a cable moves a door inside the water valve, which modulates the water flow to the heater core. Unfortunately, the flow is decreased but not by very much, since the
pressure is increased. As the pressure is increased, so is the flow, and this compensates for the door blockage. Another reason is that while the flow of water is controlled, the temperature is not. When the temperature
becomes too hot, one moves the lever toward cool, and then it is necessary to move it slightly more, more, and more, until the lever is in the cool position . At this point, the coolant now is totally blocked, and the hot air becomes cold within a few moments. So, one returns the lever to the warm position .
It is unlikely that you will have a temperature modulation concern if your coach's dash heater is equipped with a blend air door system . To determine which system the coach has, you will have to find out whather the other
end of the temperature control lever is connected to the heater case or a valve in a heater hose. If the cable leads to a water valve, similar
to the one in Figure 1, your coach has the latter type of system, and an effective and inexpensive solution exists - install a temperature control valve with an "H" in it, similar to the one in Figure 2. This revised valve is easy to install after one removes the original valve. The only addition is that it must also be installed in the heater return hose, which requires two more heater hose clamps . The "H" valve system allows the blocked coolant to flow very easily into the return line . The result is a greatly
improved system.
I have talked with the folks at Acme Radiator, and they have indicated that they will provide the "H" system heater control valve to FMCA members for $20 postage paid . To order the valve - part number 4100173 - write to Acme
Radiator and Air Conditioning Inc ., 17103 State Road 4 East, Goshen, I N 46526.
C. Jay Haynor, F15585
SECTION 2 -- HEATING AND AIR CONDITIONING GENERAL DESCRIPTION
The heating system consists of a heater core housed in a case which, typically, includes an air inlet, blower motor assembly, air distribution ducts and doors to control the flow of air through the case. The configurations of G-Series and P-Series assemblies differ .
Figure 2-1 -Heating System Diagnosis
HEATING SYSTEM TROUBLESHOOTING THE SYSTEM
Problems of too little or no heat, poor air circulation, or inadequate defrosting action are sometimes encountered with a heating system .
The diagnosis chart (Figure 2-1) lists typical trouble symptoms,the probable causes, and what can be done to correct the condition .
TROUBLE CAUSE AND CORRECTION
Temperature of heater 1. Refer to Chevrolet 10-30 Series Shop Manual.
air at outlets too low to heat up passenger,compartment .
Temperature of heater Check for body leaks such as: air at outlets adequate 1 . Floor side kick pad ventilators partially open . but the vehicle will not
2. Leaking grommets in dash. build up sufficient heat.
3. Leaking welded seams along rocker panel and windshield .
4. Leaks through access holes and screw holes.
5. Leaking rubber molding around door and windows .
6. Leaks between sealing edge of blower and air inlet assembly and dash, and
between sealing edge of heater distributor assembly and dash .
Inadequate defrosting 1 . Check that DEFROST lever completely opens defroster door in DEF position - action . Adjust if necessary.
2. Assure that temperature and air doors open fully - Adjust .
3. Look for obstructions in defroster ducts - Remove any obstructions.
4. Check for air leak in duct between defroster outlet on heater assembly and defroster duct under instrument panel - Seal area as necessary.
5. Check position of bottom of nozzle to heater locating tab - Adjust .
6. Check position of defroster nozzle openings relative to instrument panel openings.
Mounting tabs provide positive position if properly installed .
Inadequate circulation 1 . Check heater air outlet -for correct installation - Reinstall.
of heated air through 2. Inspect floor carpet to ensure that carpet lies flat under front seat and does not vehicle . obstruct air flow under seat, and also inspect around outlet ducts to ensure that carpet is well fastened to floor to prevent cupping of air flow - Correct as necessary.
Erratic heater operation . 1 . Check coolant level - Fill to proper level.
2. Check for kinked heater hoses - Relieve kinks or replace hoses.
3. Check operation of all bowden cables and doors - Adjust as necessary.
4. Sediment in heater lines and radiator causing engine thermostat to stick open -Flush system and clean or replace thermostat as necessary .
5. Partially plugged heater core - Backflush core as necessary.
Hard-operating or 1 . Check for loose bowden cable tab screws or misadjusted bowden cables -broken controls . Correct as required .
2. Check for sticking heater system door(s) - Lubricate as required, using a silicone spray.
SECTION 2-HEATING AND AIR CONDITIONING AIR CONDITIONING GENERAL DESCRIPTION
Two types of air conditioning systems are used in Chevrolet Motor Homes. For the G-Series, a blend-airsystem is used.
This system combines both the heating and cooling functionsin one unit. Cooling only is provided with the system used on the P-Series . The P-Series system is installed by the body manufacturer .
Both systems operate on the same basic principles of refrigeration. That is, a liquid refrigerant absorbs heat as it vaporizes, and loses heat as it condenses from a vapor back to a liquid . By varying the pressures within an air conditioning system, the refrigerant can be vaporized to absorb heat from inside the vehicle, and then condensed to release the heat to the outside atmosphere. System components include a compressor, condenser, expansion tube (G-Series) or a thermostatic expansion valve (P-Series), evaporator, and an accumulator or a receiverdehydrator.
In operation, the compressor produces the pressure which moves refrigerant through the system . Liquid refrigerant passing through the restriction of the expansion tube or valve changes into a vapor as it enters the low-pressure environment of the evaporator. (See Figure 2-2.)
As it changes to a vapor, it absorbs heat from the air being circulated around the evaporator. Suction created by the compressor draws the refrigerant vapor through the line from the evaporator. The vapor, which has been under low pressure, is pumped out of the compressor under high
pressure. The high pressure in this part of the system is due to the expansion tube (or thermostatic expansion valve) which places a restriction in the line. As the highpressure refrigerant vapor flows into the condenser, it changes to a liquid as it loses heat to the air flowing around
the condenser. The liquid refrigerant flows through the line from the condenser to the expansion tube (or thermostatic expansion valve) to repeat the cycle.
System temperature is controlled by running the compressor intermittently, automatically turning it on and off as necessary to maintain proper temperatures . The compressor is started and stopped through the use of an electromagnetic clutch on the compressor pulley . The clutch is operated by a pressure-sensing switch (Pressure Cycling Switch - G-Series) or a temperature-sensing switch (Thermostatic Switch - P-Series) .
In addition to the components described above, the air conditioning system is also equipped with either an accumulator (G-Series), or a receiver-dehydrator (P-Series). 2-2
RECEIVER-DEHYDRATOR P SERIES
The receiver-dehydrator, mounted near the condenser,serves as a reservoir for storage of high-pressure liquid produced in the condenser. It incorporates a screen sack filled with the dehydrating agent.
The receiver-dehydrator, used primarily as a liquid storage tank, also functions to trap minute quantities of moisture and foreign material which may have remained in the system after installation or service operations. A refrigerant sight glass is built into the receiver-dehydrator to be used as a quick check of the state and condition of charge of the entire system .
ACCUMULATOR G SERIES
The accumulator is located at the evaporator outlet . Its most important function is not to "accumulate" although this too is important. Its primary function is to separate any liquid retained in the vapor from the evaporator, retain the liquid and release the vapor to the compressor.
A bag of desiccant (dehydrating agent) is also located in the accumulator as a moisture-collecting device.
NOTE: If the refrigerant system has been opened -that is, exposed to the atmosphere - the desiccant may have' absorbed a considerable amount of
moisture . In such instances, the system must be evacuated before recharging. This process removes moisture from the system.
G-SERIES SYSTEM
Air, either outside air or recirculated air, enters the system and is forced through the system by the blower. As the air passes through the evaporator core, it receives maxImum cooling if the air conditioning controls are calling for cooling . After leaving the evaporator, the air enters the heater and air conditioner selector duct assembly where, by means of diverter doors, it is caused to pass through or to bypass the heater core in the proportions necessary to provide the desired outlet temperature. Then conditioned air enters the vehicle through either the floor distributor duct or the dash outlets . During cooling operations, the air is cooled by the evaporator to below comfort level, it is then warmed by the heater to the desired temperature. During "heating only" operations, the evaporator will not be in operation and ambient air will be warmed to the desired level in the same manner.
The diverter doors which direct the air flow through this system are operated by the vacuum motors. The A/C control unit is positioned between the vacuum source and the motors to direct the application of vacuum as required .
SECTION 2-HEATING AND AIR CONDITIONING ELECTROMAGNETIC CLUTCH "HPV"
COMPRESSOR P-SERIES COMPRESSOR ELECTROMAGNETIC/ CLUTCH "HPV" . r
G-SERIES CONDENSER DESICCANT BAG LIQUID LINE CONDENSER 7n
"LPV/Ipl"
"HPL"
RECEIVERDEHYDRATOR
EXPANSION
TUBE (ORIFICE)
"LPL"
LIQUID LINE
2-3
"HPL" J "LPL"
HPV - HIGH-PRESSURE VAPOR
HPL - HIGH-PRESSURE LIQUID
LPV - LOW-PRESSURE VAPOR
LPL - LOW-PRESSURE LIQUID
Figure 2-2- Basic Air Conditioning System -Refrigeration Schematic
THERMOSTATIC EXPANSION VALVE THERMOSTATIC SWITCH EVAPORATOR
PRESSURE CYCLING SWITCH "LPV" OIL BLEED HOLE "LPV/I I" DESICCANT BAG
SECTION 2 -- HEATING AND AIR CONDITIONING
P-SERIES SYSTEM
This system performs the cooling functions only. When heating (above ambient temperatures) is desired, the vehicle heater must be used .
This self-contained unit is bracket mounted to the dash by the motor home manufacturer . It operates on inside (recirculated) air only. Air is drawn into the unit, passed through the evaporator core (receiving maximum cooling) and then directed into the vehicle through adjustable outlets .
A thermostatic switch, located on the face plate is used to control compressor operation by sensing air temperature as it leaves the evaporator core.
MAINTENANCE AND INSPECTION
There are two sections to the air conditioning system . The first section includes the refrigeration components-compressor,condenser, evaporator, etc . The second section includes the air distribution components such as the blower, case assembly, diverter doors, vacuum lines and motors, etc .
Maintenance and inspection procedures are directed to each of these sections . Of course, for the P-Series, the air distribution section is quite simple and does not include the many components used in the G-Series.
REFRIGERATION SECTION CAUTION : BECAUSE OF THE NATURE OF REFRIGERANT-
12 AND THE HIGH PRESSURES WHICH ARE PRESENT IN THE REFRIGERANT SECTION OF THE SYSTEM, PERSONAL INJURY CAN RESULT IF ESTABLISHED DIAGNOSTIC AND SERVICE PROCEDURES ARE NOT FOLLOWED. THEREFORE, ALL SUCH WORK REQUIRED ON THE SYSTEM SHOULD BE REFERRED TO A QUALIFIED SHOP WITH THE NECESSARY TRAINED PERSONNEL AND EQUIPMENT.
THE FOLLOWING PROCEDURES ARE INTENDED TO IDENTIFY OR AVOID POTENTIAL PROBLEM
CONDITIONS.
Inspection
Perform the following checks regularly :
1 . Check outer surfaces of radiator and condenser cores to be sure they are not plugged with dirt, leaves or other foreign material . Be sure to check between the condenser and radiator as well as the outer surfaces.
2. Check the metal tubing lines to be sure they are free of dents or kinks which can cause a loss of system capacity due to a line restriction .
3. Check the flexible hose lines for brittleness or deterioration which could cause a system leak.
4. Check for proper drive-belt tension .
2-4
Operational Quick Checks
The following checks may indicate if the amount of refrigerant (charge) in the system is low. The ambient temperature must be above 70°F.
NOTE: Engagement of the compressor clutch in both of the tests below indicates that the clutch electrical circuit is O.K. If the clutch does not engage, then check for a blown fuse, loose connections or damaged
or deteriorated wires. If these checks are O.K., then the problem may be in the compressor clutch or switch. Take the vehicle to a qualified shop for further testing.
G-SERIES
1 . Prepare the motor homes as follows :
Engine must be warm (CHOKE OPEN and OFF FAST IDLE SPEED CAM) and at normal idle speed.
Hood and body doors open .
Selector (mode) lever set at NORM.
Temperature lever at COLD.
" Blower on HI .
2. With the compressor engaged, place your hand first on the evaporator inlet pipe (between the expansion orifice and evaporator), and then on the accumulator can surface (Figure 2-3) .
" The temperature should feel the same for both and somewhat cooler than the ambient temperature.
If the inlet pipe feels cooler than the accumulator surface, the system's refrigerant charge is probably low.
Figure 2-3 - Checking Evaporator Inlet and Accumulator Temperatures (G-Series)
P-SERIES (WITH SIGHT GLASS)
At temperatures higher than 70°F, the sight glass may indicate whether the refrigerant charge is sufficient. A shortage of liquid refrigerant is indicated after about five minutes of compressor operation by the appearance of slow-moving bubbles (vapor) or a broken column of refrigerant
under the glass. Continuous bubbles may appear in a properly charged system on a cool day. This is a SECTION 2 normal situation . If the sight glass is generally clear and performance is satisfactory, occasional bubbles do not
indicate a refrigerant shortage.
If the sight glass consistently shows foaming or a broken liquid column, it should be observed after partially blocking the air to the condenser. If under this condition the sight glass clears and the performance is otherwise satisfactory, the charge shall be considered adequate.
NOTE: The sight glass is located on or near the receiverdehydrator.
AIR DISTRIBUTION SECTION
Electrical Circuit Diagnosis
The blower electrical circuit and motor are O.K. if the blower operates at all of the designated speeds. If the lower does not work at all, then check for a blown fuse, loose connections, and for damaged or deteriorated wires .
If these checks are O.K. and/or the blower does not operate at all speeds, then the problem may be in the switch, relay or motor. Take the vehicle to a qualified shop for further testing .
Vacuum System Diagnosis (G-Series)
If the air is not flowing through the proper outlets (floor, dash, or defroster), then there may be a problem in the vacuum system, or with the diverter doors. Check the doors to see that they operate properly and do not bind. Next, check all vacuum hoses and connections between the vacuum source, A/C control and vacuum motors for leaks. If any hoses are damaged or deteriorated, they HEATING AND AIR CONDITIONING should be replaced . If the hoses are O.K., the problem may be in the control assembly or vacuum motor(s). Take the vehicle to a qualified shop for further testing .
OPTIONAL AIR CONDITIONING SYSTEM
The factory installed air conditioning system has made several changes since first made available in the 1986 Class A chassis. The next several pages attempt to assist with part numbers and description of the items
installed by Chevrolet or the coach builder.
Only parts of the A/C system are installed on the chassis as the coach body is installed by the coach builder whose responsibility is to complete the system including proper charging with freon and' wiring system to insure proper operation . Those items not listed with part numbers are installed by the coach builder .
1986 thru mid year 1989, A/C systems and repair parts were provided by ARA Manufacturing Co. in Grand Prairie, TX. However, they are out of business and their surplus parts were sold to Acme Radiator and A/C Inc ., 17103 State Road 4 East, Goshen, IN 46526, Phone (219) 534-1516.
1989 to present the parts are provided by Wynns Inc . and most parts can be obtained through the General Motors dealers. Assistance for NPN Wynns parts can be obtained by calling 1-800-347-3883 1900 S.E. loop 820, Ft. Worth, TX 76140.
OPTIONAL AIR CONDITIONING SYSTEM
For 1986, at the request of several RV manufacturers, GM has made available the underhood portion of the air conditioning system as an available option' - Option Number 7N4. GM can, as ordered, produce the engine
mechanical air conditioning parts, as furnished by ARA Manufacturing Company. .
APPENDIX 2-1
The following illustrations and part number listings (both GM production numbers and corresponding ARA part numbers) are provided as an aid to the motor home owner concerning installation, repair and replacement of air conditioning system Option Number 7N4 . This system became standard start-of-production 1988. (See NOTE on page 2-7.)
Figure A2-1-1 -Chevrolet Motor Home Chassis Compressor Assembly 2-62 .18_ -
50 -0GHI A. ,o I
NOTE: SEE APPENDIX A - DRIVE BELTS AND TENSION SPECIFICATIONS FOR GM BELT NUMBERS MOUNT ANDDRIVE ASSEMBLY PARTSUST No. ARA PART NO. DESCRIPTION QUANTITY GM PROD. NO. 1 7045871 Compressor Mount 1 (14100871) 2 7045872 Compressor Mount Support 1 (14100872) 3 7045873 Compressor Brace 1 (14100873) 4 7045833 Compressor Adjusting Arm 1 (14100874) 5 7045824 Compressor Adjusting Block 1 (14100875) 6 5004112 Idler Spacer, 1-3/8" Long 1 (14100875) 7 1502902 Carton 1 Bolt Kit. Consisting of : (1) 1/4" x 4" NC (AI Thread) Bolt (1) 3/8" x 5-1/4" NC Bolt 8 7004312 (2) 3/8" x 7/8" NC Bolt (1) 1/4" Flatwae 1 (14100875) (3) 3/8" x 1-1 /2" NC Bolt (8) 3/8" r
(3) 3/8" x 1-3/4" NC Bolt (6) 3/8" (SAE) Flatwasher _ (1) 3/8" x 4-1/4" NC Bolt (1) 3/8" NC Hex Nu 9 5001018 Idler Spacer, 9/16" Long (Required on vehicles with single Air Injection Pump) 10 0329174 Compressor No . 709 "Sanden" Clutch, 5-1/4" Diameter 1 (15578925) NOTE: The following parts are all listed under the GM Part No . 14100875 : Compressor Adjusting Block
Idler Spacer, 1-2/8" Long Bolt Kit. Consisting of: (See Above Listing)
APPENDIX 2- 1
OPTIONAL AIR CONDITIONING SYSTEM
Figure A2-1-2-Chevrolet Motor Home Chassis Condenser Assembly
2-7
GM RETRO-FIT
"A" CHASSIS EVAPORATOR ASSEMBLY * FUSE BOX
LIQUID REAR DISCHARGE EVAPORATOR COIL HOSE __ COMPRESSOR EXPANSION * CONDENSER VALVE FAN HARNESS DISCHARGE HOSE ELECT RELAY'
SUCTION HOSE FAN RELAY" qIII*III* I
HEATER CORE I I-
NIPPLES I I _
HEATER HOSES
_
SWITCH
CONNECTOR
' , I
DENOTES PARTS FURNISHED °' 1111
WITH EVAPORATION KIT INSTALLED .
BY RV MANUFACTURER
PART OF GM OPTION NO. 7N4 (PRE-1988 UNITS)
NOTE: AIR CONDITIONING SYSTEM DESCRIBED ABOVE BECAME STANDARD EQUIPMENT WITH
START OF PRODUCTION 1988, EXCEPT WHEN UNIT WAS ORDERED AND BUILT WITH
OPTION - AIR CONDITIONING DELETE, AS INDICATED ON THE SERVICE PARTS
IDENTIFICATION LABEL (SEE PAGE 1-3). THIS SITUATION WOULD REQUIRE THE
MANUFACTURER TO INSTALL THEIR OWN AIR CONDITIONING SYSTEM .
BASIC CHANGE FOR INTERIM 1990 MODEL IS USE OF ONE 16 INCH FAN
REPLACING TWO 10 INCH FANS STARTING 11-13-89.
_ CONDENSER ASSEMBLY PARTS LIST
No. ARA PART NO. DESCRIPTION QUANTITY GM PROD. NO.
1 0519336 1985-1/2 Condenser Assembly without engine oil cooler 1 (15547181)
1 0519406 1987 to Current Condenser Assembly with engine oil cooler in bottom 1 (15578281)
(Shown above)
2 0570689 Mtg. Hardware, Consisting of Screw #14 x 3/4 HWH Z/P D/P 10
3 0884940 Switch, Coolant Temperature 1 (15547201)
APPENDIX 2- 1
OPTIONAL AIR CONDITIONING
SYSTEM (Cont'd)
Figure A2-1-3 -Chevrolet Motor Home Chassis Condenser Kit -Without Engine Oil Cooler (19851 /2 -1987)
2-8
19 18
11
25
16 23 26
17 I \, 6
7 24 5
,.
15 15
22 9 8
to 16 5
6 13
2
3 4 15
CONDENSER KIT PARTS LIST(without Oil Cooler)
No. ARA PART NO. DESCRIPTION QUANTITY GM PROD. NO.
'1 . 0519369 Coil Condenser 1 15547181
2 1273235 Receiver-Drier 1 15547182
3 0319606 Bracket, Mounting Receiver-Drier 1 15547188
4 1900157 Sticker, Caution 1
5 0039851 Screw, #8 x 1/2 HWH 20
6 0319647 Bracket, Condenser Mounting 2 15547189
7 0996400 Grommet-Condenser Mt Brkt Ground Wire 1 15547190
8 0058337 Coupling-Receiver Drier 1 15547183
9 0543513 'O' Ring-Receiver Drier Outlet 1 15547184
10 0059605 'O' Ring #6-Receiver Drier Inlet 1 15547185
11 0059606 'O' Ring Valve H ose 2 15547186
12 0059706 'O' Ring Valve Ca 1 15547187
13 0964045 Condenser Fan Assy .
- 2 15547191
14 1701620 Guard, Fan 2 15547193
15 1016434 Seal, Condenser Fan 4 15547194
16 0319387 Bracket, Condenser Seal Mounting 2 15547195
17 1016433 Seal, Condenser to Radiator 2 15547196
18 0986195 Hose, Discharge #8 1 15547198
19 0548325 Service Valve, Discharge 1 15547199
20, 0049849 Cap, Aluminum 1 15547200
21 0876802 Terminal, Adapter 1 15547197
22 0319563 Bracket, Adapter 2 15547669
23 0039852 Bolt, 1/4-20 x 5/8" HH ZIP 8
24 0039853 Lockwasher, Star 1/4" ZIP 1
25 0039855 Lockwasher, 1/4" ZIP 7
26 0039854 Starwasher #10 1
APPENDIX 2-1
OPTIONAL AIR CONDITIONING
SYSTEM '
Figure A2-1-4 - Chevrolet Motor Home Chassis Condenser Kit -With Engine Oil Cooler (1988 -1991)2-9 6 2019 7 6 16 i 17 1 28 I( 27 9 I, l17 II18134
14316 29 24 11 14255 - 26 14 122 13815 23 CONDENSER KIT PARTS LIST (with Oil Cooler)
NO. ARAPARTNO. DESCRIPTION QUANTITY GM PART NO.
1 0519405 Coil Condenser 1 15578281
2 1273235 Receiver-Drier 1 15547182
3 0058337 Fitting, Self Sealing 1 15547183
4 0543513 ORing Special 1 15547184
5 0059605 ORing #6 1 15547185
6 0059606 ORing #8 2 15547186
7 0559607 ORing #10 1 15547187
8 0319606 Bracket, Receiver-Drier Mounting 1 15547188
9 0320184 Bracket Condenser Fan Mounting (Upper) 1 15578282
10 0996400 Grommet Lavelle #917 1 15547190
11 0964045 Condenser Fan and Seal Assembly 2 15547191
12 0964040 Blade Fan 2 15583108
13 1701620 Fan Guard 2 15547193
14 1016434 Seal, Fan/Condenser 4 15547194
15 1900157 Caution Label 1 NCSI
16 0319387 Bracket, Condenser Seal Mounting 2 15547195
17 1016433 Seal, Condenser to Radiator 2 15547196
18 0876802 Terminal Adapter 1 15547197
19 0986306 Hose, #8 Discharge 1 15584784
20 0548325 Service Valve Discharge 1 15547199
21 0049849 Cap, Aluminum 1 15547200
22 0543516 #8 2 14055585
23 0039851 Screw, #8 x 1/2" HWH Z P 20 15547360
24 0319563 Bracket, Adapter 2 15581669
25 1120235 Motor, DC 2 15583107
26 0320185 Bracket, Condenser Fan Mounting Lower 1 15578283
27 0409443 Hose Clam 1/2" 1
28 0022151 Bolt, 1 4 20 x 5/8" HH 8
29 0049887 Shipping Cap 2
APPENDIX 2-1
AIR CONDITIONING
SYSTEM
CONDENSER KIT PARTS LIST with 011 Cooler
Figure A2-1-5 - Chevrolet Motor Home Chassis Condenser Kit - With Engine Oil Cooler (1990 Interim)2-10
NO. PART NO. DESCRIPTION QUANTITY
1 0519557 Coil Condenser 1
2 1273235 Receiver-Drier 1
3 0058337 Fitting, Self Sealing 1
4 0543513 0 Ring Special 1
5 0059605 0 Ring #6 1
6 _005_9606 0 Ring #8 2
7 0559607 0 Ring #10 1
8 0319606 Bracket, Receiver-Drier Mounting 1
9 0321934 Bracket Condenser Fan Mounting (Upper) 1
10 0996500 Grommet Lavelle #917 1
11 0964045 Condenser Fan and Seal Assembly 2
12 0964115 16" Fan Assembly 2
13 1701620 Fan Guard 2
14 1016434 Seal, Fan/Condenser 4
15 1900157 Caution Label 1
16 0319387 Bracket, Condenser Seal 2
17 1016433 Seal, Condenser to Radiator 2
18 0876802 Terminal Adapter 1
19 0986307 Hose, #8 Discharge 1
20 0548325 Service Valve Discharge 1
21 0049849 Cap, Aluminum 1
22 0039851 Screw, #8 x 1/2" HWH Z P 20
23 0319563 Bracket, Adapter 2
24 N55 see 12 Motor, DC 2
25 0321935 Bracket, Condenser Fan Mounting (Lower) 1
26 0986968 Inlet Tube 1
27 0986967 Outlet Tube 1
28 O Ring #8 4
APPENDIX 2-1
OPTIONAL AIR CONDITIONING SYSTEM (Cont'd)
GM PART
NO. 15604813
ARA P/N 0986421
HOSE, OIL COOLER
OUTLET
GM SUPPLIED
HOSE CLAMPS (2)
GM SUPPLIED
BOLTS (2)
GM PART
NO. 15604811
ARA P/N 0986420
HOSE, OIL COOLER
INLET
GM PART NO. 14055585
ARA P/N 0543516 /
"O" RINGS (2)
NOTE: Interim 1990 will have metal lines 1988-1989.
GM PART NO. 14055585
ARA P/N 0543516
RINGS (2)
OIL HOSES
FROM ENGINE,
GM PART
NO. 15578281
ARA P/N 0519406
CONDE14SER ASSEMBLY
WITH ENGINE OIL
LOWER
RADIATOR
SUPPORT
Figure A2-1-6 - Chevrolet Motor Home Engine Oil Hose Kit 2-11
APPENDIX 2-1
OPTIONAL AIR CONDITIONING SYSTEM (Cont'd)
DK. BLUE/RED
HARNESS SYSTEM PART NOS .
0885033, 0885132, AND 6499142
Of BLACK/WHITE
DK. BLUE/RED
RED RED
RED
SWITCH
UE
BLACK/WHITE
30 AMP FUSE
DK. BLUE
DK. BLUE/WHITE
NORMALLY OPEN .
CLOSES TO GROUND
AT 225 PSI .
REFRIGERANT PRESSURE
STARTER
SOLENOID
DK. BLUE
TO A/C CONTROL
PANEL HARNESS
(DK. BLUE/RED)
+ HOT W/IGN. ON
COOLANT TEMPERATURE
SWITCH LOCATED IN LEFT
TANK OF RADIATOR
NORMALLY OPEN.,
CLOSES TO GROUND
AT 221 °F APPROX.
GROUND
GROUND
CONDENSER FANS *
NOTE: Wiring shown is not supplied or installed by GM through 1990. Shown as an aid to the technician as typical of manufacturers' installations of wiring purchased from ARA.
NOTE: Starting with the 1991 Class A motorhome, the A/C condenser fan is wired by Chevrolet through the main front end engine wiring harness . The coolant temperature switch is now located in the RH cylinder head with a green wire.
NOTE: Dual 10" fans are standard with Chevrolet installed A/C from 1986 through interim1990. Interim 1990 changes to one 16" fan November 13, 1989. VIN L3315231
Figure A2-1-7 - Typical ARA Wiring Diagram - Class "A" RV Condenser with Fans
APPENDIX
OPTIONAL AIR CONDITIONING SYSTEM (Cont'd)
A/C CONDENSER & BLOWER MODULE ASSEMBLY
Effective 11-13-89
VIN 11-3305628
Condenser #15643270
Metal Lines
14054378
14054379
Interim 1990
Inlet Hose 15557762
Outlet Hose 15557765
Fittings 14055586
RADIATOR LOWER
MOUNTING PANEL
(138)
Figure A2-1-8 - Oil Cooler Lines P300 (32 52) & L19 & Env.
APPENDIX OPTIONAL AIR CONDITIONING SYSTEM
1991 P3(32) ENGINE OIL COOLER (WIL1917.4N & A/C)
(32)
NOTE: QUANTITY IS ONE PER VEHICLE UNLESS OTHERWISE SPECIFIED.
4
Figure A2-1-9 - 1991 P3(32) Engine Oil Cooler
DEFINITIONS
- A/C ENGINE PROVISIONS
- EXC A/C
1 . N.S. CONDENSER, A/C (P3 32 W/7.4N)('1) SINGLE FAN 1990-1992 . . . . . . . . . . . . . . . . . . . . . . . . 15643270
3.430 BOLT, W/CON WA, HEX (P3 32 W/7.4N)(AS REQD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3997227
2. 1 .540 BRACKET, ENGINE OIL COOLER HOSE (P3 32MAN) . . . .
14054335
3. 8.900 BOLT, HFH (M8X1 .25X18)(AS REQD) . . . . . . .
12337905
4. 1 .540 CONNECTOR, ENGINE OIL COOLER HOSE (P3 32 W/7.4N) . . . . . . . . . . . . . . . . . . . . . . . . . 15654938
5 1 .540 FITTING, ENGINE OIL COOLER HOSE (P3 32MAN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15538480
6. 1.540 HOSE, ENG OIL COOLER INLET (P3 32 MAN & ENV, EXC EN2) . . . . . . . . . . . . . . . . . . . . . 15638189
1 .540 HOSE, ENG OIL COOLER INLET (P3 32 W/7AN & EN2, EXC ENV) . . . . . . . . . . . . . . . . . . . . . 15638187
7. 1.540 HOSE, ENG OIL COOLER OUTLET (P3 32 MAN & ENV. EXC EN2) . . . . . . . . . . . . . . . . . . . 15638190
1 .540 HOSE, ENG OIL COOLER OUTLET (P3 32 W/7.4N & EN2, EXC ENV) . . . . . . . . . . . . . . . . . . . 15638188
8. 1 .540 CLIP, ENGINE OIL COOLER HOSE (P3 32 W/7.4N)(AS REQD) . . . . . . . . . . . . . . . . . . . . . . . . 15517986
9. 9.190 BOLT, W/LOCKWASHER A/C EVAP & BLO MDL (AS REQD) . . . . . . . . . . . . . . . . . . . . . . . . . 14030698
10. 8.977 SCREW, W/FLAT WASHER, HEX TAP (M3X1AX16)(AS REQD) . . . . . . . . . . . . . . . . . . . . . . 11509371
APPENDIX 2-4
OPTIONAL AIR CONDITIONING
SYSTEM (Cont'd)
1991-1992 P3(32) ENGINE OIL COOLER (L1917.4N)(WIC60)
NOTE: QUANTITY IS ONE PER VEHICLE UNLESS OTHERWISE SPECIFIED. TP01-313
Figure A2-1-10 - 1991-1992 P3(32) Engine Oil Cooler
NOTE 1 : SEE ILLUSTRATION IN 9.000 FOR FURTHER DETAILS.
RPO DEFINITIONS
C60 - AIR CONDITIONER FRONT, MANUAL CONTROLS
ENV - AIR CONDITIONING ENGINE PROVISIONS
EN2 - AIR CONDITONING, DELETE
2-15
1 . 1.540 BRACKET, ENGINE OIL COOLER HOSE (P3 32 W/7.4N) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14054335
2. 8.900 BOLT, HFH (M8X1 .25X18)(AS REQD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11513703
3. 1.540 CONNECTOR, ENGINE OIL COOLER HOSE (P3 32 W/7.4N) . . . . . . . . . . . . . . . . . . . . . . . . . 15654938
4. 1 .540 FITTING, ENGINE OIL COOLER HOSE (P3 32 W/7.4N) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15538480
5. 1.540 HOSE, ENGINE OIL COOLER INLET (P332 W/7.4N & ENV. EXC EN2) . . . . . . . . . . . . . . . . . . 15638189
1.540 HOSE, ENGINE OIL COOLER INLET (P3 32 W/7.4N & EN2, EXC ENV) . . . . . . . . . . . . . . . . . . 15638187
6. 1 .540 HOSE, ENGINE OIL COOLER OUTLET (P3 32 W/7.4N & ENV. EXC EN2) . . . . . . . . . . . . . . . . 15638190
1 .540 HOSE, ENGINE OIL COOLER OUTLET (P3 32 W/7.4N & EN2, EXC ENV) . . . . . . . . . . . . . . . . 15638188
7. 1.540 CLIP, ENGINE OIL COOLER HOSE (P3 32 W/7.4N)(AS REQD) . . . . . . . . . . . . . . . . . . . . . . . . 15517986
8. 1.540 TUBE, OIL COOLER INLET (P3 32 W/7.4N & C60) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15665135
9. 8.900 BOLT, HEX (5/16-18X3/4)(AS REQD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9440967
10. 8.950 CLAMP, LOOP CUSHIONED (AS REQD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2041644
11 . 9.220 TUBE, AIR CONDITIONER OUTLET (P3 32 W/7.4N & C60) . . . . . . . . . . . . . . . . . . . . . . . . . . . 15665136
12. 8.950 STRAP, METRIC PLASTIC ADJUSTABLE TIE (215MM LENGTH)(AS REQD) . . . . . . . . . . . . . 11501906
13. N .S. CONDENSER, AIR CONDITIONER (P3 32 W/7.4N)(*1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15687269
14. 8.977 SCREW, W/FL WASHER, HEX TAP (M6.3X1 .8X16)(AS REQD) . . . . . . . . . . . . . .
.
. . . . . . . . . . . 11509371
OPTIONAL AIR CONDITIONING
SYSTEMS (Cont1d)
1994 AIR CONDITIONING
THE GOOD AND BAD OF CFCs
When R-12 (often referred to by its brand name Freon) was introduced in 1930, the industry hailed it as a miracle chemical . It was non-poisonous, easy and cheap to manufacture and quite stable. The first in the family of chlorofluorocarbons (CFCs) yet to come, R-1 2's apparent stability and
low cost made air conditioning the creature comfort of the 20th century. Of all the R-12 manufactured, about twothirds is used to service automotive air conditioners . Unfortunately, recent scientific findings prove that we may have a big price to pay in the future for the comfort we've 3 .
enjoyed in the past. The findings show thatCFCs, like R-12 are depleting the Earth's protective ozone layer located in the stratosphere some 10 to 30 miles above the planet's surface . This precious layer of ozone filters out most of the sun's harmful ultraviolet rays.
THE CLEAN AIR ACT AMENDMENTS OF 1990
The most important part of the amendments to Section 609 of the Federal Clean AirAct have to do with servicing motor vehicle airconditioning and technician certification . The act states :
Servicing Motor Vehicle Air Conditioners - Effective January 1, 1992, no person repairing or servicing motor vehicles for consideration may perform any service on a motor vehicle air conditioner involving the refrigerant for
such air conditionerwithout properly using approved refrigerant
recycling equipment and no such person. may perform such service unless such person has been_ properly trained and certified .
R134A REFRIGERANT
The change to R1 34A will be effective with the 1994 model chassis beginning in August 1993. The changes that are required to accept this new refrigerant on factory installed components on the P30 motor home chassis will affect those components added by your coach builder to complete
the system .
SYSTEM DIFFERENCES
1 . Condenser
a. Width and Height the same
b. Thickness changes from 1 .4" to 1 .85"
APPENDIX 2-5
c. Inlet and outlet fittings - metric thread
d. Service valve-located at condenser inlet instead of compressor
e. Will be PRECHARGED
f. Wynn's climate system .
2. A/C Compressor
a. Lubricating oil is different than R-12 Systems. Oil used is Sanden SP-20 (GM part #15959132).
b. Plumbing connections are clamp on, rather than threaded to prevent intermixing R-12 compressors and R-1 34A compressors .
A/C Plumbing
a. The liquid line, from the receiver drier to the evaporator will be provided by the body builder. The receiver drier end of the line will have a metric quick connect fitting.
b. The suction line from the evaporator to the compressor
will be provided by the body builder. The compressor fitting end of the hose will have to match. This fitting is currently manufactured by S&H Fabricating, Walled Lake, Michigan. The line must be equipped with a quick connect gauge fitting .
4. A/C Evaporator
a. The evaporator outlet must be equipped with a suction service valve similar in arrangemenht to the condenser discharge line.
GENERAL INFORMATION
1 . Dedicated equipment is required to recycle, evacuate, and charge R-134A Systems. Do Not mix R-12 and R-1 34A. Contamination and damage to your coach will result.
2. It requires a different desiccantand highersystem pressure and more airflow across the condenser.
3. GM approves only the following A/C hoses and tube suppliers for our vehicles. This is based on extensive lab tests which include pressure and temperature cycling, vibration tests, and moisture ingression testing,
and field trials in car and truck fleets across the country.
These suppliers are familiar with all the GM fitting designs, testing requirements, etc . Only two hoses, are GM approved for use with R-134a. They are Parker P-90 Hose and Goodyear 4680 Hose. The coupling suppliers are:
Parker Automotive Products
Cleveland, Ohio
(216) 531-3000
APPENDIX 2-5
S&H Fabricating 4. The A/C Compressors are shipped from the factory with
Walled Lake, Michigan the proper oil charge for the system .
(313) 624-1661
5. You should expect the identical performance from your Fayette Tubular Products R-1 34A System as your old R-12 System.
Fayette, Ohio
(419) 237-2531 A/C Compressor L19 Gas #15680077 Sanden
L65 Diesel #1136400 Harrison
SECTION 3-STEERING, SUSPENSION, WHEELS AND TIRES FRONT ALIGNMENT
GENERAL DESCRIPTION
The term "front alignment" refers to the angular relationships between the front wheels, the front suspension attaching parts and the ground.
The pointing in or "toe-in"'of the front wheels, the tilt of the front wheels from vertical (when viewed from the front of the vehicle) and the tilt of the suspension members from vertical (when viewed from the side of the vehicle), are all involved in front alignment.
CASTER
Caster is the tilting of the front steering axis either forward or backward from the vertical (when viewed from the side of the vehicle) . A backward tilt is said to be positive (+)
and a forward tilt is said to be negative (-). (See Figure
3-1 .)
CAMBER
Camber is the tilting of the front wheels from the vertical when viewed from the front of the vehicle. When the wheels tilt outward at the top, the camber is said to be positive (+). When the wheels tilt inward at the top, the camber is said to be negative (-). The amount of tilt is measured in degrees from the vertical and this measurement is called the camber angle. (See Figure 3-1 .)
TOE-IN
Toe-in is the turning in of the front wheels. The actual amount of toe-in is normally only a fraction of an inch . The purpose of a toe specification is to ensure parallel rolling of the front wheels. (See Figure 3-1 ;)
Toe-in also serves to offset the small deflections of the wheel support system which occur when the vehicle is rolling forward. In other words, even when the wheels are set to toe-in slightly when the vehicle is standing still, they tend to roll parallel on the road when the vehicle is moving .
It should be noted that excessive toe-in or toe-out will cause tire wear.
CENTERLINE CENTERLINE OF VEHICLE OF WHEEL CAMBER ANGLE FRONT VIEW
POSITIVE CAMBER -WHEEL TILTS OUTWARD AT TOP AS SHOWN e NEGATIVE CAMBER -
FRONT WHEEL TILTS INWARD 90° AT TOP POSITIVE DIRECTION WHEEL TOE-IN
TOP VIEW CENTERLINE OF WHEEL
1-.,-CENTERLINE OF
BALL JOINT AXIS
POSITIVE CASTER -
AXIS TILTS BACK
AT TOP AS SHOWN
CASTER ANGLE
SIDE VIEW
NEGATIVE
CASTER - AXIS
TILTS FORWARD
AT TOP
POSITIVE
DIRECTION
Figure 3-1 -Caster, Camber and Toe-in
SECTION 3
MAINTENANCE AND INSPECTION
There are several factors which can affect front alignment.
These factors include tire inflation pressures, the condition
of wheel bearings, steering and suspension components.
They are the basis for the following checks which can
indicate problems that should be corrected.
1 . Check all tires for proper inflation pressures and approximately
the same tread wear.
2. Check front wheel bearings for looseness .
3. Check for looseness of ball joints, tie rod ends and
steering relay rods and damper.
4. Check for excessive run-out of wheels and tires.
5. Check for a difference in the ride height between right
and left sides of the vehicle . (See Figure 3-2.)
NOTE : Excessive or unevenly distributed loads also affect
ride height and alignment . This should be
taken into consideration when making the check.
Also, if the motor home is equipped with air bag
cylinders, it is important that the cylinders be inflated
to the proper pressure for the load being
carried, in order to maintain adequate ride height.
(See Air Bag Cylinder Inspection information in
the Suspension section of this manual .)
6. Check for steering gear looseness at frame.
7. Check for improperly operating shock absorbers .
There may be evidence of a leaking shock(s) .
WHEEL ALIGNMENT SPECIFICATIONS - CASTER
DIMENSION "A"/"BC"
'~ Toe-in was reduced from 5/16 inch in 1985 as part
of a GM trend reducing toe-in. If equipped with
radial tires, some tire manufacturers would suggest
toe-in specifications of 1/32 inch to 1/8 inch .
NOTE: 60 minutes equal 1 degree.
Figure 3-3-Alignment Specifications
STEERING, SUSPENSION, WHEELS AND TIRES
3-2
CHECK RIDE HEIGHT MEASUREMENT (REFERRED
TO AS EITHER DIMENSION "A" OR "BC") BETWEEN
BRACKET AND CROSS MEMBER FLANGE. MEASUREMENT
MUST BE PERPENDICULAR TO CROSS
MEMBER FLANGE. MEASUREMENT IS "IRON TO
IRON." RUBBER BUMPER IS NOT INCLUDED.
LOWER CONTROL ARM
BRACKET
Figure 3-2- Ride Height Measurement
8. Check for loose control arms.
9. Check for loose or missing stabilizer bar attachments.
10. Steering and vibration complaints are not always the
result of improper alignment . An additional item to be
checked is the possibility of tire lead due to worn or
improperly manufactured tires. "Lead" is the deviation
of the vehicle from a straight path on a level road
without hand pressure on the steering wheel.
Tire balance should also be checked .
NOTE: Alignment should be done with the unit fully
loaded .
Refer to Frame Angle Measurement Information in this
section of the manual for correction to caster procedure .
(IN .) 1-1/2 1-3/4 2 2-1/4 2-1/2 2-3/4 3 3-1/4 3-1/2 3-3/4 4 4-1/4 4-1/2 4-3/4 5
G-10, 20 3-1/2° 3-1/4° 3° 3° 2-3/4° 2-1/2° 2-1/4° 2° 2°, 1-3/4° 1-1/2°
G-30 2-3/4° 2-1/2° 2-1/4° . 2° 1-1/2° 1° 3/4° 1/2° 1/4° 0° -1/40
P-20, 30 3° 2-1/2° 2-1/4° 2° 1-3/4° 1-1/2° 1-1/4° 1° 1/2° 1/2° 1/4° 0°
MOTOR HOME
(32) 5-1/2° 5-1/4° 5° 4-3/4° 4-1/2° 4° 3-3/4° 3-1/2° 3-1/4° 3° 3°
1-BEAM AXLE (OPTION FS3)
TOE-IN (IN.) 3/16 t 1/16
CASTER'` +2-1/2 0 f 1/2 0
CAMBER +1-1/2° t 1/2°
KING PIN INCLINATION
(NOT ADJUSTABLE)
70 10"
MODEL CAMBER TOE-IN (IN .)
G10, 20 .5° 3/16
G30 .2° 3/16
MOTORHOME (32) 0.1 0 3/64 ± 1/64'"
SECTION 3
ALIGNMENT CHECK
The caster, camber and toe-in specifications for both the
G- and P-Series chassis are shown in Figure 3-3. The
caster specifications will vary depending on the ride height
measurement shown in Figure 3-2 . This measurement is
commonly referred to as either Dimension "A" or Dimension
"BC" depending upon your reference source. This
dimension is also affected by rear axle imbalance of
weight (left to right) . See Rear Suspension section of this
manual for further information.
Another factor which will affect the caster measurement
is the frame angle (Figure 3-4) . Frame angle should be
taken into account when determining the proper caster
setting .
Figure 3-4 - Frame Angle Measurement
FRAME ANGLE MEASUREMENT
To determine the frame angle:
1 . Park the motor home on a level surface .
2. Place a protractor with a level gage against the bottom
of a straight section of the frame rail near the chassis
midpoint .
3. Determine the angle the frame rail slopes from level.
NOTE: Determine if the vehicle has either an up-in-rear
measurement or a down-in-rear measurement.
STEERING, SUSPENSION, WHEELS AND TIRES
4. Determine the caster setting following the procedures
in the appropriate shop manual.
5. Compute the actual caster setting from the frame angle
and caster measurement taken as follows :
(a) A down-in-rear frame angle must be subtracted
from a positive caster specification .
(b) An up-in-rear frame angle must be added to in
the appropriate shop manual.
(c) A down-in-rear frame angle must be added to a
negative caster.specification.
(d) An up-in-rear frame angle must be subtracted
from a negative caster specification .
LOWER BALL JOINT INSPECTION
Lower ball joints are a loose fit when not connected to the
steering knuckle. Wear may be checked without disassembling
the ball stud, as follows :
1 . Support weight of control arms at wheel hub and drum .
2. Accurately measure distance between tip of ball stud
and tip of grease fitting below ball joint.
3. Move support to control arm to allow wheel hub and
drum to hang free. Measure distance as in Step 2. If
the difference in measurements exceeds 2.38 mm
(.094 or 3/32 inch) for all models, the ball joint is worn
and should be replaced . (See Figure 3-5.)
Figure 3-5- Lower Ball Joint Check
SECTION 3-STEERING, SUSPENSION, WHEELS AND TIRES
STEERING SYSTEM
The steering system consists of the steering linkage, steering
gear, steering pump; hoses, and the steering column
and wheels. Vehicle direction is controlled from the steering
wheel. Rotating the steering wheel rotates the input
shaft (wormshaft) on the steering gear by means of a shaft
in the steering column. Rotation of the wormshaft transfers
this motion to the output shaft of the steering gear. The output
shaft of the gear controls the directional position of the
front wheels (right or left depending on input) through a
series of arms or levers referred to as the steering linkage .
A damper incorporated into the linkage helps to control the
road shock transmitted to the linkage from the wheels .
STEERING LINKAGE
GENERAL DESCRIPTION
The steering linkage is located forward of the front cross
member. The P-Series linkage is illustrated in Figure
3-6 . Steering effort is transmitted to left- and right-hand
adjustable tie rods through a relay rod. The relay rod is
connected to an idler arm on the right and to the pitman
arm on the left.
P-SERIES
SUPPORT ASSEMBLY
* ADJUSTMENT:
End Play should be 0 to .003 inch .
Side-to-side clearance requires
bushing replacement (GM Part No. 266316).
Figure 3-6 -Steering Linkage
MAINTENANCE AND INSPECTION
LUBRICATION OF STEERING LINKAGE
The steering linkage under normal conditions should be
lubricated with any water-resistant EP-type chassis lubricant
every 7,500 miles or six months, whichever occurs
first. Lubricate every 3,000 miles or two months whichever
occurs first when operating in dusty or muddy conditions,
or if the vehicle is used "off-road ."
STEERING LINKAGE, SUPPORT
ASSEMBLIES (P-SERIES)
The fit of the shafts in the linkage support assemblies
(Figure 3-6) should be tight with end play not exceeding
.003 inch . Check the end play. If the end play exceeds
.003 inch in either assembly, adjust it to within 0 to .003
inch . Loosen large lock nut torque cap to 25' Ibs.and then
loosen 1/16 turn and tighten lock nut . If there is side play,
replace the bushings (GM Part No. 266316) in the affected
assembly.
STEERING DAMPER CHECK
The type of steering damper shown in Figure 3-7 is nonadjustable,
nonrefillable and is not repairable. At each
lubrication interval, perform Check No. 1 and No . 2 on the
steering damper system.
Check 1
Check the damper attachments to be sure they are properly
and securely installed . (Tighten, if loose.) The damper
assembly should be replaced if the rubber bushings are
badly worn .
Check 2
Inspect the damper for evidence of fluid leakage. A light
film of fluid is permissible on the body of the damper near
the shaft seal. A dripping damper should be replaced .
Check 3
Turn the steering wheel so as to extend the piston rod
from the damper body. If the piston rod is rusted badly,
replace the damper. If rust is light, clean the rod. Use care
so that the rod surface is, not damaged.
NOTE: On vehicles left in long-term storage, the piston rod
may become quite rusted. The rod must be
cleaned before the vehicle is moved. Failure to
clean the rod will destroy the seals with the first
inward movement of the rod - making replacement
of the damper a certainty.
If the damper is not functioning properly, and/or is noisy,
refer to a qualified service shop.
SECTION 3
RELAY & TIE
ROD ASSEMBLY
a
O
TORQUE TO 45 FT. LBS .
MAXIMUM TORQUE OF 60 FT. LBS.
PERMISSIBLE TO ALIGN COTTER
PIN SLOT (1/16 TURN MAXIMUM) . DO
NOT BACK OFF NUT FOR COTTER
PIN INSERTION.
9420821 . . . . . . . .
9440974 . . . . . . . .
FRAME 9436771 . . . . . . . .
357545 . . . . . . . . .
4
6
NUT
NUT
COTTER PIN
ARM ASSEMBLY STEERING
IDLER & SHOCK ABSORBER
FRONT CROSS MEMBER
NOTE: TORQUE TO 90 IN. LBS.
OBTAIN TORQUE BY RUNNING
FIRST NUT TO UNTHREADED
PORTION OF SHOCK END.
TORQUE JAM NUT AFTER
TORQUING FIRST NUT.
Figure 3-7- Steering Damper
POWER STEERING SYSTEM
GENERAL DESCRIPTION
The optional power-assist steering utilizes the steering
column and linkage previously described. However, the
steering gear is different. It combines hydraulic pressure
with the mechanical force of a manual steering system to
reduce the steering effort required. In addition to a redesigned
steering gear, the system requires a pump with
pressure and return hoses connecting it to the steering
gear. The pump, driven by a belt from the crankshaft,
circulates the hydraulic fluid through the steering gear.
Valves in the steering gear which are controlled by the
steering wheel direct the flow of fluid as appropriate for
right or left vehicle turns.
The steering gear is of the recirculating ball type. This
gear provides for ease of handling by transmitting forces
from the wormshaft to the pitman shaft through the use
of ball bearings in the same way as the manual steering
gear.
MAINTENANCE AND INSPECTION
Complaints of faulty steering are frequently the result of
problems other than the steering gear or pump. Those
areas of the steering system which can be easily checked
and quickly corrected without disassembly and overhaul
of any major components should be attempted first.
STEERING, SUSPENSION, WHEELS AND TIRES
Conditions such as hard or loose steering, road shock or
vibrations are not always due to the steering gear or pump,
but are often related instead to such factors as low tire
pressure and front-end alignment . These factors should
be checked and corrected before any adjustment or disassembly
of the power steering gear or pump is
attempted .
Many factors affect power operation of the steering system
of which the most common are:
1 . Fluid level and condition .
2. Drive belt tension .
3. Loose component mountings.
4. Loose pump pulley .
5. Excess front axle weight.
These factors must be checked and corrected before making
any further diagnosis of the steering system.
After the source of the problem has been found, determine
the cause. For example, if the oil level in the reservoir is
found to be low, refill and check the entire hydraulic system
for oil leaks. Refilling the reservoir will not necessarily
correct the problem.
GM PART NO.
79-94:22134593
85-92. P3 with FS3 ABSORBER ASM-IDLER
r 22046454
3798007 . . . . ., . . RETAINER
6270752 . . . . . . . . GROMMET
SECTION 3-STEERING, SUSPENSION, WHEELS AND TIRES
HARD STEERING AT ENGINE IDLE
The P-Series motor home power steering assist system
is designed for good response up to the 5,000-Ib. suspension
capacity. Complaints of little or no steering assist
while at idle or with the driver's foot applying the brake
are usually the result of the suspension being at or very
near capacity. The reason this occurs is that the Hydro-
Boost system has taken some power away from the steering
assist system. At this point, the power steering assist
system is at borderline capacity.
This situation can be corrected by removing the pressure
on the brake. This will return the necessary pressure to
the steering assist system allowing proper power steering
assistance. Also, if additional weight were added to the
front axle there would be a momentary system stall requiring
slight movement of the vehicle in order to "feel"
the power steering assist system operating . GM cannot
endorse overloading . To avoid problems concerning overloading,
move some load rearward to remove some of the
weight from the front axle. Axle weight should never exceed
tire or axle capacity. Refer to the proper shop manual
for the power steering pump pressure checking
procedures.
NOTE : Typical P-Series - Commercial power steering
pump pressure is 1,200-1,300 PSI. Typical
P-Series - Motor home power steering pump
pressure is 1,350-1,450 PSI.
In order to improve static steer effort on the P30
(motor home chassis, the steering gear has been
changed on all 14,500) - 14,800-16,000 GVW
Figure 3-8- Power Steering Pump Gear Box Leak Points
chassis effective on V.I.N. N3310596. Th e new
710 gear ratio is 17.5:1 and the older 708 gear was
14:1 . The new 710 gear cannot be installed on the
older units due to numerous changes and
supports.
LEAKAGE CHECK
If you suspect leakage in the power steering system, follow
the guidelines listed below. In some cases you will
be able to locate the leak easily, but seepage leaks may
be more difficult .
1 . With the vehicle's engine off, wipe the complete power
steering system dry (gear, pump, hoses, and
connections) .
2. Check oil level in pump's reservoir and adjust as
required.
3. Start engine and turn steering wheel from stop to stop
several times. Do not hold in corner for any length of
time as this can damage the power steering pump. It
is easier if someone else operates the steering wheel
while you search for the seepage.
4. Find the exact area of leakage. Potential leak points
are shown in Figure 3-8.
Some leaks can be corrected easily . (See Quick Fixes) .
Refer the problem of more extensive leaks to a qualified
serviceman for repair .
SECTION 3-STEERING, SUSPENSION, WHEELS AND TIRES
QUICK FIXES
The purpose of this section is to acquaint you with the
types of leakage that can be repaired very easily . It contains
information on reservoir oil level, the hoses and the
hose connections.
An overfilled pump reservoir can be a cause for leakage
complaint . The oil in the steering system expands as
heated during normal usage. If overfilled, the excess is
forced through the breather cap hole and may be sprayed
over the engine by air blast. Operate the engine and steering
system until normal operating temperature is obtained .
Remove the reservoir cap and check the graduated level
on the dipstick. Adjust the oil level as required.
Seepage at the hose connections can be a cause for
leakage complaint and can be due to loose connection
nuts. If leakage is observed at the hose connections, and
the nut is not cross threaded, tighten the nuts at the gear
to 30 ft. lbs. of torque.
The nut at the power steering pump should be tightened
to 40 ft. lbs. of torque. If tightening to this torque does not
stop the leak, refer to the appropriate shop manual. If
either the return hose or pressure hose leaks, replace the
hose.
After the source of a leak has been found and corrected,
refill the system with GM Power Steering Fluid (GM Part
No. 1050017 - quart size) or equivalent. Avoid the use
of automatic transmission fluid in the power steering system
since it does not contain the additives necessary for
good seal life. In an emergency situation, automatic transmission
fluid can be used to "get home." However, it
should be replaced with power steering fluid as. soon as
is practical .
Figure 3-9 - Power Steering Reservoir
3-7
NOTE: Noise in the power steering system on the 14,500
and 14,800 Ib GVW chassis may be the result of
air in the system . Air in some cases may be
trapped at the high point in the steering line from
the reservoir to the steering pump. The air being
trapped in this line is the result of line routing in
relationship to the pump reservoir . Correct this
condition by raising the reservoir 4 inches upward
from the present location on the dash and toe
panel - see Figure 3-9. This will route the hoses
above the steering pump and eliminate the high
point where air is being trapped. The above was a
production change in November 1992 beginning
with V.I.N. 306209.
NOTE: See page 6 Bulletin 90-391-5 Automatic Park
System.
CAUTION: Automatic transmission fluid should never
be used in the power steering system if the unit is
equipped with option F44 -Automatic Park Brake
System on the 16000#chassis .
NOTE: Contamination in the power steering system
(metal flakes) can be removed by installing an
A/C filter #25010169 AC-PF 883 in the power
steering return line. The filter element should
be checked to insure filter doesn't restrict the
flow of returning fluid .
Component Replacement
Lip seals, which seal rotating shafts, require special treatment.
This type of seal is used on the steering gear at
the .pitman shaft, at the stud shaft, and on the drive shaft
of the pump. When leakage occurs in one of these areas,
refer the problem to a qualified serviceman for repair.
PUMP BELT TENSION ADJUSTMENT
1 . Loosen pivot bolt and pump brace adjusting nuts as
required .
NOTE: Do not move pump by prying against reservoir or
by pulling on filler neck, or damage to the pump
could occur.
2. Move pump, with belt in place until belt is tensioned
to the specifications . (See Appendix A - Drive Belts
and Tension Specifications at the back of this manual.)
3. Tighten the pump brace adjusting nut . Then tighten the
pivot bolt nuts.
4. Recheck the pump belt tension . Adjust as necessary.
SECTION 3-STEERING, SUSPENSION, WHEELS AND TIRES
SUSPENSION SYSTEM
The function of the suspension system is to support the
vehicle body and chassis over the tires and wheels, and
to absorb and cushion road shock. The springs in the
suspension cushion the ride while the shock absorbers
dampen or control the excess motion (up-and-down
bounce) caused by variations in the road surface . The
designs of the front and rear suspensions are different,
but their function is the same.
FRONT SUSPENSION
GENERAL DESCRIPTION
The G- and P-Series vehicles incorporate an independent
coil spring front suspension system, as shown in Figure
3-10. The control arms are of unequal length (S.L.A.
Type) .
This suspension system consists of upper and lower control
arms pivoting on steel threaded or rubber bushings
on upper and lower control arm shafts . The lower control
arms are attached to the cross member. The upper control
arms are attached to a frame bracket . These control arms
are connected to the steering knuckle through pivoting
ball joints.
A coil spring is located between the lower control arm and
a formed seat in the suspension cross member, thus the
lower control arm is the load-carrying member. Doubleacting
shock absorbers are also attached to the lower
control arms and connect with the frame to the rear on
the upper end. The front wheel bearings are tapered roller
type and are used on all models.
Some P-Series motor homes may be equipped with air
bag cylinders to increase the load-carrying capacity of the
front suspension . These cylinders are positioned in the
center of the coil springs .
FRONT
SUSPENSION
UNIT
LOWER
CONTROL
ARMS
CONTROL ARM SHAFTS
Figure 3-10- Independent Front Suspension -
Typical
3-8
MAINTENANCE AND INSPECTION
The front suspension must be lubricated periodically in
accordance with the Maintenance Schedule. Grease fittings
are indicated in the Lubrication section of this
manual.
When the suspension is being lubricated, the components
should also be checked for obvious signs of damage or
wear. Leakage from the shock absorbers may indicate a
need for replacement.
WHEEL BEARING LUBRICATION
As a part of normal service, the front wheel bearings
should be removed, cleaned, inspected and lubricated
each 12,000 miles. Repack the wheel bearings with hightemperature
melting grease - approximately 500°F (GM
Part No. 1051344 or equivalent) . Refer to the appropriate
Chevrolet Light-Duty Truck Shop Manual for the
procedure .
WHEEL BEARING ADJUSTMENT CHECK
NOTE: Tapered roller bearings are used on all series
vehicles and they have a slightly loose feel when
properly adjusted. A design feature of front-wheel
tapered roller bearings is that they must NEVER
be preloaded . Damage can result by the steady
thrust on roller ends which comes from
preloading .
1 . Raise the vehicle and support it at the front lower control
arm .
2 . Spin the wheel to check for any unusual noise or
roughness.
3. If the bearings are noisy, tight, or excessively loose,
they should be removed, cleaned, inspected and lubricated
prior to adjustment. If it is necessary to inspect
bearings, refer to the appropriate Chevrolet Light-Duty
Truck Shop Manual .
To check for tight or loose bearings, grip the tire at the
top and bottom and move the wheel assembly in and out
on the spindle . Measure movement of hub assembly, if
movement is less than .001 inch or greater than .005 inch,
adjust bearings per the following adjustment procedure .
WHEEL BEARING ADJUSTMENT
1 . Remove the hub cap or wheel disc from the wheel.
2. Remove the dust cap from the hub.
3. Remove the cotter pin from the spindle and spindle
nut .
SECTION 3-STEERING, SUSPENSION, WHEELS AND TIRES
4.
5.
6.
7.
8.
Tighten the spindle nut to 12 ft. lbs. while turning the
wheel assembly forward by hand to fully seat the
bearings. This will remove any grease which could
cause excessive wheel bearing play later. Refer to
Figure 3-11 .
Back off the nut to the "just loose" position.
Hand tighten the spindle nut. Loosen the spindle nut
until either hole in the spindle lines up with a slot in
the nut, (not more than 1/2 flat).
Install the new cotter pin. Bend the ends of the cotter
pin against the nut. Cut off the extra length to ensure
that the ends will not interfere with the dust cap.
Measure the looseness in the hub assembly. There
will be from .001 to .005 inch end play when properly
adjusted .
9. Install the dust cap on the hub.
10. Replace the wheel cover or hub cap.
2 . TIGHTEN'THE NUT -
TO 12 FT. LBS. FULLY
SEAT BEARINGS
- THIS OVERCOMES
ANY BURRS ON
THREADS./
3. BACK OFF NUT
UNTIL JUST
LOOSE POSITION .
5 . LOOSEN NUT UNTIL EITHER HOLE IN THE SPINDLE
LINES UP WITH A SLOT IN THE NUT-THEN INSERT
COTTER PIN .
NOTE: BEND ENDS OF COTTER PIN AGAINST NUT. CUT
OFF EXTRA LENGTH TO PREVENT INTERFERENCE
WITH DUST CAP
6 . WHEN THE BEARING IS PROPERLY ADJUSTED THERE
WILL BE FROM .001- .005 INCH END-PLAY
(LOOSENESS).
Figure 3-11 -Wheel Bearing Adjustment
3-9
11 . Lower the vehicle to the ground.
12. Perform the same operation for each front wheel.
AIR BAG CYLINDER INSPECTION
The air bag cylinders should be inspected periodically for
signs of deterioration or damage. Air bag leaks can easily
be checked on the vehicle . Inflate with a small amount of
air conditioning freon No . 12 then locate the leak using
an air conditioning leak detector. To check for possible
leaks with the air bag removed from the vehicle, submerge
the air bag in water and check for bubbles. (Replace with
GM Part No. 367762.) Inflation pressures should be maintained
at 10 PSI minimum to avoid chafing . Under load,
40-50 PSI is recommended for a 4,300-Ib . suspension, 50
PSI for a 5,000-lb . suspension. 70 PSI is required on the
5,300-Ib suspension . 80-90 PSI is recommended for the
F44 5,500-Ib . optional 16,000-Ib . suspension. This unit
uses an Airlift HD bag Part No. 15631881 . Vendor #40-571
NOTE: Air bags are currently used on nearly all motor
homes and are proposed for use on some GSeries
(cut-away) models for 1988-89 .
SERVICE TIP - (For units that appear somewhat low in
front due to operating at near front suspension capacity.)
1 . Jack up the motor home by the middle of the front
cross member and allow the wheels to hang .
2. Remove the air from the air bag and reinflate the air
bag to the proper pressure.
3. Lower the unit and bleed off air (as necessary) to maintain
proper air bag pressure.
This may provide some ride height improvement as the
air bag tends to stretch lengthwise slightly with this
procedure .
VEHICLE RIDE HEIGHT-FRONT COIL
SPRING/AIR BAG REPLACEMENT
The motor home owner should be cautioned in the use
of some after-market front coil springs currently available .
Some after-market front coil springs are merchandised as
a method to increase ride height for the motor home. To
obtain this additional ride height, manufacturers have increased
the diameter of the wire slightly and added one
extra coil. However, use of these after-market springs
should be considered very risky for the motor home owner.
GM recommends the use of only factory-approved replacement
parts for this "safety-sensitive" area of the vehicle.
Some after-market coils are physically too large for
the normally designed working area of the front coil spring
as the wheel goes through its ride travel. On crush, these
after-market springs can create a metal-to-metal "coilbound"
condition before the ride stops come into play.
(The damage created by using a metal-to- metal solid coil
can be compared to installing a piece of well casing in
SECTION 3 STEERING, SUSPENSION, WHEELS AND TIRES
place of a spring, then raising the vehicle in the air and
dropping the vehicle to the ground.) The force of this
metal-to-metal "coil-bound" condition is transferred directly
into the potential destruction of the lower ball joints
or broken lower control arms. The addition of a spring
shim (donut-type spacer) has a similar effect of promoting
a "coil-bound" condition .
Complaints of air bag failures are also the result of these
after-market front coil springs . The springs have a tendency
to "pinch" the air bag between the coils on crush.
Front coil springs should ONLY be replaced by a qualified
service shop. Access to the front coil spring and the air
bag is gained by lowering the lower control arm .
CAUTION : USE ONLY GM APPROVED REPLACEMENT
PARTS FOR THIS SAFETY-SENSITIVE AREA
OF THE VEHICLE.
1984 to Current . . . . . . . . . . . . . . . . . . GM Part No. 14054345
Prior to 1984 . . . . . . . . . . . . . . . . . . . . . . . . GM Part No. 472222
NOTE : 1984 to current front springs (GM Part No .
14054345) can be used for 1983 and prior years
that require front spring GM Part No. 472222 .
This will raise the front of the vehicle 3/8 inch to
1/2 inch measured at the "A/BC" measurement
location shown in Figure A3-2-1 . Study Figure
A3-2-1 at the back of this section of the manual
to determine if the useful life of the front coil
springs is exhausted and replacement of the front
coil springs is necessary.
SHOCK ABSORBER DIAGNOSIS
(Follow the Procedures Outlined Below in the Order
Indicated .)
Inspection and Ride Test :
TIRE PRESSURE-Check the tire pressure and compare
it to the recommended specification on the GVW label in
the motor home . Adjust the pressure to specification as
required. Poor vehicle control and ride complaint are
caused in many cases by improper tire inflation .
SPECIAL SUSPENSION EQUIPMENT - Check the
Service Parts Identification Sticker for any special suspension
equipment, such as a heavy-duty suspension.
Vehicles equipped with this type of option have a somewhat
stiffer or harsh ride, and this should be kept in mind.
Stiffness may occur while vehicle is still new (under 5,000
miles) . The ride should improve somewhat after 7,000 to
8,000 miles.
VEHICLE LOAD CONDITIONS - Unusual load conditions
can affect the ride and handling of the vehicle . If
unusual loading is apparent, check the distribution of this
weight. Note if it is all toward one side of the vehicle or
at the extreme rear of the vehicle . Reposition load as
required to obtain a more uniform weight distribution .
The importance of a near equal Rear Axle-to-Frame/Sideto-
Side Measurement cannot be overstressed . This near
equal measurement has a direct effect on desirable vehicle
handling and on the front-end alignment "A or BC"
dimension (with independent suspension) . Generally, a
near equal "D" dimension (see Figure 3-12) at the rear
axle is needed in order to obtain an acceptable front-end
alignment .
However, the motor home owner should be cautioned in
the use of certain after-market suspension devices. These
devices are merchandised as leveling devices to raise the
"sagging" rear of the vehicle which may be caused by an
overload situation or a weight distribution problem. Some
of these after-market leveling devices severely limit the
wheel travel that was designed into the GM chassis.
The following case study is presented as an aid to the motor
home owner in identifying potentially dangerous aftermarket
vehicle leveling devices.
GM CASE STUDY: A motor home was loaded to a maximum
GVW, both front and rear. Sufficient air was applied
to a typical after-market leveling device to establish a
"dead-level" frame. In this case study, wheel travel was
limited to 3/4 inch before the after-market device "went
solid metal-to-metal" between the rear axle and the frame.
This severe limitation on wheel travel promoted a "crashthrough
situation" on even the slightest bump. The force
from this "crash-through situation" was transmitted into
the vehicle frame, rear axle and the coach itself . GM has
determined that these types of after-market leveling devices
can be very damaging to the motor home and also
can affect vehicle handling and are therefore potentially
very dangerous .
If vehicle weights cannot be shifted due to vehicle build,
consideration should be given to adding spring leaves or
spacer blocks.
Fioure 3-12 - Rear Axle-to-Frame/Side-to-Side
Measurement
SECTION 3
If the vehicle is within the rear spring rating but heavier
on one side (tending to lean toward the generator or some
other heavy appliance), you might consider adding a
spacer block of sufficient thickness to equalize the left/
right axle-to-frame measurement. Spacer blocks are not
sold as GM parts but are fabricated at local machine
shops. Installation of a spacer block and/or spring leaf is
not covered by the GM warranty. The following information
is provided as an aid to the motor home owner for loading
situations.
NOTE : The addition of a spacer block can actually improve
overall ride quality while the addition of a
spring leaf tends to reduce the ride quality of the
vehicle .
Spacer blocks can be added to either side or both sides
of the vehicle and of different thickness to equalize or
"open up" the "D" dimension shown in Figure 3-12.
Spacer blocks are generally 21 /2 inches wide by 6 inches
long and are installed between the spring pack and spring
seat. (See Figure 3-13.) The thickness of the spacer block
(to equalize left/right side dimensions) is determined by
measuring the "D" dimension on each side and then subtracting
one side's dimension from the other. The result
is the thickness of the spacer block required for the low
side of the vehicle .
Raising the back of the vehicle is generally trial and error.
This is accomplished by driving the vehicle over stacked
pieces of plywood 1/2 inch to 1 inch thick (in a level area)
and checking that the side trim of the vehicle is level with
each height increase . When the side trim is level and eye
appealing to the owner, measure the height of the pieces
of wood and add spacer blocks to equal that measure-
SPACER BLOCK
EQUALS THE
LENGTH AND
WIDTH OF SPRING
SEAT ON AXLE HOUSING
Figure 3-13- Spacer Block
STEERING, SUSPENSION, WHEELS AND TIRES
3-1 1
ment. With most motor homes, you can add a spacer block
of approximately 3/4 inch without replacement of the
U-bolts. A minimum of 2 full threads on the U-bolt must
extend thru the nut .
CAUTION : AS THE BACK OF THE VEHICLE IS
RAISED, THE REAR HYDRAULIC FLEXIBLE BRAKE
HOSE (RUNNING FROM FRAME MIDPOINT TO THE
AXLE) IS EFFECTIVELY SHORTENED. DAMAGE CAN
RESULT TO THE REAR HOSE WHEN THE AXLE
DROPS AWAY FROM THE VEHICLE TO THE LOWER
END OF THE WHEEL TRAVEL (WHEN THE VEHICLE
ENCOUNTERS A CHUCK HOLE). CHECK TO MAKE
SURE THAT THE REAR HOSE IS LONG ENOUGH TO
AVOID DAMAGE IN SUCH A SITUATION. IF THERE IS
ANY DOUBT, REPLACE THE REAR HOSE WITH A
LONGER HOSE AND THEN BLEED THE BRAKES.
DRIVE LINE ANGLE MAY ALSO BE AFFECTED.
The spacer block has a 3/4-inch hole drilled in the center.
A slip-fit dowel, as long as the thickness of the spacer
block, is inserted into the hole of the block. The center
bolt head of the spring pushes the dowel down into the
pocket in the spring seat and extends into the axle housing
seat hole, as shown in Figure 3-14.
3/4" HOLE
AND SLIP-FIT
DOWEL
DOWEL EXTENDED
INTO AXLE HOUSING
SEAT HOLE
Figure 3-14- Spacer Block Positioning
NOTE: There are several different spring center bolt head
sizes available . The P-Series motor home chassis
requires a 3/4-inch spring center bolt head
size.
VEHICLE RIDE AND HANDLING CHECK - After completing
the previous checks, drive the vehicle to determine
if the problem has been corrected or to definitely establish
the type of problem that still exists. If the problem still
exists (poor handling, bottoming, noise, ride sway, etc .),
the shock absorbers may be the cause. Refer to the appropriate
Chevrolet Light-Duty Truck Shop Manual for
more extensive test procedures.
SECTION 3
REAR SUSPENSION
GENERAL DESCRIPTION
STEERING, SUSPENSION, WHEELS AND TIRES
Both the G- and P-Series vehicles use a leaf spring/solid
rear axle suspension system .
NOTE: 1993 SOP the 14,500-14,800-16,000# units are
equipped with the new taper leaf spring .
The rear axle assembly is attached to multi-leaf springs
by U-bolts .The spring front eyes are attached to the frame
at the front hangers, through rubber bushings. The rear
ends of the springs are attached to the frame by the use
of shackles which allow the spring to "change its length"
while the vehicle is in motion. Control arms are not required
with leaf springs . (See Figure 3-15.)
Ride control is provided by two identical direct doubleacting
shock absorbers angle-mounted between the
frame and brackets attached to the axle tubes .
On G-Series vehicles, the shock absorbers are mounted
to the front of the axle on the right side, and to the rear
of the axle on the left side. For P-Series vehicles, both
right and left shock absorbers are mounted to the front of
the axle.
MAINTENANCE AND INSPECTION
Since the rear springs and shock absorbers use rubber
bushings in the mounts, no lubrication is required . However,
inspect the suspension periodically for worn or damaged
components such as weak or broken spring leaves,
leaking shock absorbers, and loose or broken mounting
bolts, etc . Check for uniformity of ride height between right
and left sides. Replace any worn or damaged parts.
Rear shock absorbers should be inspected and their operation
checked following the same procedures for shock
absorbers listed in this section under Front Suspension .
Figure 3-15- Rear Spring Installation -
G-Series -- Typical
The U-bolts attaching the rear axle to the leaf springs
should be checked and retightened to the specified torque
after the first 500 miles of vehicle operation . Recheck the
U-bolt torque each 10,000 miles thereafter. Torque specifications
are listed in the chart which follows :
U-BOLT TORQUES- REAR
19
3-1 2
Rear shock frame brackets can be purchased
separately if damaged or broken. Item No. 2.
1985-92 178" W13 L.H. No. 15638125
1988-92 208" WB R.H. No. 15638126
Model Bolt Diameter Torque
G-10,20 . 9/16 in. 115-130 ft. lbs .
G/P-20,30 5/8 in. 125-175 ft. lbs.
P-30 3/4 in. 200 ft. lbs .
SECTION 3-STEERING, SUSPENSION, WHEELS AND TIRES
WHEELS AND TIRES
Use the proper size torque wrench when installing wheels.
Hand tightening without a torque wrench or the use of a
power impact tool can result in installation torques which
are too high or too low. It will help prevent loosening, of
the wheel stud nuts and excessive stress placed on the
stud bolts.
GENERAL DESCRIPTION
The factory-installed tires and wheels are designed to
operate satisfactorily with loads up to and including the
full rated load capacity when inflated to the recommended
inflation pressures .
Correct tire pressures and driving techniques have an
important influence on tire life. Heavy cornering, excessively
rapid acceleration, and unnecessarily sharp braking
increase tire wear.
MAINTENANCE AND INSPECTION
TIRE INSPECTION AND ROTATION
Front and rear tires-perform different jobs and can wear
differently depending on the type of roads driven, individual
driving habits, etc . To obtain maximum tire life, tires
should be inspected at intervals shown in the Maintenance
Schedule. For the longest tire life, anytime irregular wear
is noticed, the tires should be inspected and rotated and
the cause of the uneven wear corrected. Be certain to
check wheel nut tightness (using a torque wrench) and to
adjust the tire pressures, front and rear, after rotation to
agree with the recommended pressures . Recheck the
torque (Figure 3-18) at 100 and 1,000 miles of operation
after wheel installation, then, once every 6,000 miles
thereafter. '
The outer tire on a dual wheel will skid or drag on a turn.
because of the difference in the turning radii of the inner
and outer tires. This results in faster wear of the outer tire.
In general, the tire with the largest diameter or least wear
should be positioned at the outside of each dual wheel.
In addition, when vehicles are operated continuously on
high-crown roads an increase in air pressure of from 5 to
10 PSI in the outside tire of each dual produces maximum
tire life.
The "X Method" of rotation is recommended with radial
tires. Due to their design, radial tires tend to wear
faster in the shoulder area particularly in the front positions.
This makes regular rotation especially necessary .
With dual wheel installations, it is recommended that the
circumference of each tire to be installed on the rear axle
be measured with a steel tape. If all tires do not measure
the same, the two larger tires should be installed on one
side and the two smaller tires on the opposite side.
3- 1 3
INFLATION PRESSURE
The maximum cold inflation pressures for the factoryinstalled
tires are listed on the Certification Label. (See
Figure 3-16.) Tires must be inflated to these pressures
when the Gross Vehicle Weight Rating (GVWR) or a
Gross Axle Weight Rating (GAWK) is reached. For partial
or uneven load distributions (front to rear), proper tire
inflation pressure can be determined from the procedure
under Determining Wheel/Tire Loads in this section . Improper
tire inflation pressures for the load the vehicle is
carrying can adversely affect tire life and vehicle
performance.
Figure 3-16 -Certification Label
For improved ride comfort in vehicles rated at 8,600 lbs.
GVWR, it is permissible to use the lower tire pressure
values shown on the label located on the rear edge of the
driver's door provided there is a maximum of 200 lbs.
cargo, no slide-in camper, and there are three or fewer
occupants. The lower GVWR and GAWR (rear) reflect the
maximum load-carrying capacity of the tires at lower
pressure.
Too low an air pressure can result in tire overloading,
abnormal tire wear, adverse vehicle handling, and reduced
fuel economy. The tire flexes more and can build
up excessive heat, weakening the tire and increasing susceptibility
to damage or failure. Too high an air pressure
can result in abnormal wear, harsh vehicle ride, and increased
susceptibility to damage from road hazards.
Lower inflation pressures should be used only with reduced
vehicle loads and the rear tire pressure should be
equal to or greater than the front pressure on single wheel
application . After determining the load on each tire by
weighing the vehicle on a scale, the correct cold inflation
pressures for the actual tire loads can be obtained from
the Tire/Wheel Load and Inflation Pressure Charts shown
in Figure 3-17. Refer to the owner's and driver's manual
for additional information on inflation pressure.
DETERMINING WHEEL/TIRE LOADS
To determine the load carried by each wheel and tire,
weigh the motor home in two stages. First, position the
vehicle with the front wheels on the scale, and take a
SECTION 3 STEERING, SUSPENSION, WHEELS AND TIRES
weight reading. Divide this reading by two to determine
the load carried by each tire/wheel. Next, position the
vehicle with the rear wheels on the scale, and take the
second weight reading . Divide this reading by two (single
rear wheels) or four (dual rear wheels) to determine the
tire/wheel loads. Then, inflate tires to the proper pressure
as determined by load. (See Figure 3-17.)
WHEEL AND TIRE BALANCING
It is desirable from the standpoints of tire wear, vehicle
ride and handling ease to maintain proper balance of
wheel and tire assemblies on all models. This may be
accomplished by either of the two types of balancing systems
in current use which balance wheels either on the
vehicle or off. The "on the vehicle" type, however, is the
more desirable in that all rolling components (brake
drums, bearings, seals, etc.) are included in the balancing
procedure and thereby have any existing unbalance cor-
G-SERIES
rected . Because of the specialized equipment required,
wheel and tire balancing should be performed by a qualified
service shop.
TIRE REPLACEMENT
When replacing tires, be sure to consult your owner's and
driver's manual for information regarding the proper tire
selection . Use of the incorrect size or type of tire may
affect load-carrying capacity, ride, handling, speedometer/
odometer calibration, vehicle ground clearance,
and tire clearance to the body and chassis. If replacing
only a single tire, it should be paired on the same axle
with the least worn tire of the others.
CAUTION : DO NOT MIX DIFFERENT TYPES OF TIRES
ON THE SAME VEHICLE SUCH AS RADIAL, BIAS, AND
BIAS-BELTED TIRES EXCEPT IN EMERGENCIES, BECAUSE
VEHICLE HANDLING MAY BE SERIOUSLY AFFECTED
AND MAY RESULT IN LOSS OF-CONTROL.
(TIRE AND WHEEL LOAD LIMITS ARE SHOWN BELOW. VEHICLE LOADING MUST BE LIMITED SUCH THAT
NEITHER THE WHEEL LOAD LIMITS NOR TIRE INFLATION ARE EXCEEDED.)
TIRE SIZE AND LOAD LIMITS-LBS.
*`NOTE: Wheel code is located on the wheel just to the right of the valve stem hole.
G-SERIES
WHEEL CODE AND LIMITS
Figure 3-17-Tire/Wheel Load and Inflation Pressure Charts
3-1 4
TIRE TIRE REV. LOAD INFLATION PRESSURE - PSI
SIZE PER MILE RANGE
~
30 35 40 45 50 55 60 65 70 75 80
BIAS TIRES USED AS SINGLES
8.00-16.5 734 C 1360 1490 1610 1730
8.00-16.5 734 D 1360 1490 1610 1730 1840 1945 2045
8.75-16.5 712 D 1570 1720 1850 1990 2110 2240 2350
8.75-16.5 712 E 1570 1720 1850 1990 2110 2240 2350 2470 2570 2680
BIAS TIRES USED AS DUALS
8.00-16.5 734 C 1195 1310 1415 1520
8.00-16.5 734 D 1195 1310 1415 1520 1620 1710 1800
RADIAL TIRES USED AS DUALS
8.75R16.5 712 E 1570 1720 1850 1990 2110 2240 2350 2470 2570 2680
MAX.
CODE WHEEL MAX. LOAD PRESSURE
SIZE LBS. PSI
YD 16.5x6 2680 85
YH 16.5x6 2680 85
YJ 16.5x6.75 2680 85
NO CODE 15x6 .5 JJ 1690 40
MAX. MAX.
CODE
WHEEL , LOAD PRESSURE
SIZE
LBS. PSI
BR 15x7 JJ 1690 40
CD 15x6.5 JJ 1690 40
XH 15x6 JJ 1585 40
XW 15x6 JJ 1910 70
SECTION 3 - STEERING, SUSPENSION, WHEELS AND TIRES
(TIRE AND WHEEL LOAD LIMITS ARE SHOWN BELOW, VEHICLE LOADING MUST BE LIMITED
SUCH THAT NEITHER THE WHEEL LOAD LIMITS NOR TIRE INFLATION PRESSURE ARE EXCEEDED.)
P-SERIES
RADIAL TIRE SIZE AND LOAD LIMITS -LBS.
BIAS TIRE SIZE AND LOAD LIMITS -LBS.
WHEEL;CODE AND LIMITS
Figure 3-17 -Tire/Wheel Load and Inflation Pressure Charts (Continued) See Owners Manual
3-15
TIRE SIZE TIRE REV. LOAD INFLATION PRESSURE -PSI
PER MILE RANGE F 35 45 50 60 65 75 80
FRONT METRIC RADIAL TIRES USED AS SINGLES
LT215/85R16 682 C 1495 1785 1940
LT215/85R16 682 D 1495 1785 1940 2180 2335
LT235/85R16 653 D 1700 2030 2205 2623
LT235/85R16 653 E 1700 2030 2205 2485 2623 2905 3042
REAR METRIC RADIAL TIRES USED AS DUALS
LT215/851316 682 C 1360 1625 1765
LT215/85R16 682 D 1360 1625 1765 1985 2150
TIRE SIZE TIRE REV. LOAD INFLATION PRESSURE-PSI
PER MILE RANGE 55 60 65 70
FRONT METRIC RADIAL TIRES USED AS SINGLES (MICHELIN)
8R19.5 617 D 2355 2517 2682 2800
REAR METRIC RADIAL TIRES USED AS DUALS (MICHELIN)
8R19.5 617 D 2287 2442 2597 2700
TIRE SIZE TIRE REV. LOAD INFLATION PRESSURE -PSI
PER MILE RANGE 30 35 40 45 50 55 60 65 70 75 90
FRONT-BIAS TIRES USED AS SINGLES
7.50-16 652 C 1620 1770 1930 2060
7.50-16 652 D 1620 1770 1930 2060 2190 2310 2440
7.50-16 652 E 1620 1770 1930 2060 2190 2310 2440 2560 2670 2780
8-19.5 613 D 2270 2410 2540 2680 2800 3170
8-19.5 613 E 3170
REAR BIAS TIRES USED AS DUALS
7.50-16 652 C 1430 1565 1690 1815
7.50-16 652 D 1430 565 1690 1815 1930 2040 2140
7.50-16 652 E 2245 2345 2440
8-19.5 613 D 2230 2350 2460
8-19.5 613 E 2230 2350 2460 2570 2680
CODE WHEEL
SIZE LOAD
LBS.
MAX.
PRESSURE PSI
AF or AR 16x6K 2440 80
CODE WHEEL LOAD MAX.
SIZE LBS. PRESSURE PSI
ZY 19.5x6 2540 80
ZT 19.5x6 2780 95
SECTION 3 - STEERING, SUSPENSION, WHEELS AND TIRES
RADIAL TIRES USED AS SINGLES
SINGLES
Two wheels are used on the assembly line that turns out the GM P-32 motorhome chassis. Chassis with gross vehicle
weight ratings (GVWR) of 10,500 pounds to 12,300 pounds use a 19.5 x 6, 8-hole wheel with a 6.5-inch bolt circle -
part number 15963341 . Chassis with a GVWR of 14,500 pounds to 16,000 pounds use a 19.5 x 6, 10-hole wheel with
a 7.25-inch bolt circle - part number 14005758.
TIRE REV. LOAD INFLATION PRESSURE- PSI
TIRE SIZE PER MILE RANGE 35 40 45 50 55 60 65
7.501316 654 D 1620 1770 1930 2060 2190 2310 2440
DUAL
7.501316 654 D 1430 1565 1690 - 1815 1930 2040 I 2140
TIRE REV. LOAD INFLATION PRESSURE - PSI
TIRE SIZE PER MILE RANGE 55 60 65 70 75 80 85
225/701319.5 646 F 2475 2650 2835 3040 3220 3405 3640
DUAL
225/701119.5 646 F 2377 2557 2755 2862 2970 3185 3415
SECTION 3 STEERING, SUSPENSION, WHEELS AND TIRES
CAUTION : USE A TORQUE WRENCH TO TIGHTEN
LUG NUTS. TIGHTENING BY HAND OR WITH AN IMPACT
WRENCH IS NOT RECOMMENDED. TORQUE
SPECIFICATIONS LISTED ARE FOR DRY THREADS
WITHOUT LUBRICATION. UNDER CONDITIONS OF
ABNORMAL CORROSION, A MODEST AMOUNT OF
LUBRICANT ON THE FIRST THREE THREADS OF THE
WHEEL STUDS SHOULD ALLEVIATE ANY DIFFICULTIES.
DO NOT USE PENETRATING OIL. DO NOT APPLY
LUBRICANT TO THE BALL SEATS OF THE
WHEELS OR TO THE BALL FACES OF CAP NUTS.
Figure 3-18- Wheel Nut Tightening Sequence and
Torque Specifications
WHEEL STUD BOLT REPLACEMENT
When one wheel stud bolt is broken on axles using fiveto
nine-bolt wheels, all stud bolts should be replaced .
When one stud bolt is broken on an axle using ten-bolt
wheels, the broken bolt, plus the adjacent bolt on each
side should be replaced . The additional stress placed on
bolts adjacent to the broken bolt weakens them and is the
reason for replacement.
TYPICAL WHEEL AND STUD BOLT
FAILURES
Worn/Broken Stud Bolts
Stripped threads on the stud bolts may be the result of
excessive torquing of the studs (Figure 3-19) or may be
the result of damage during wheel installation (when placing
the wheel over the studs) .
Figure 3-19- Stripped/Broken Wheel Stud Bolts
Broken studs are a direct result of operating with loose
cap nuts or improperly seated wheels.
Worn/Cracked Wheels
Worn wheel stud holes will usually be accompanied by
evidence of a bright, worn surface on the wheel face. This
condition indicates that loose wheels were working
against each other. As shown in Figure 3-20, the stud
holes are out of shape and a build-up of metal occurs
around them. This condition requires that the wheels be
replaced .
NOTE : Firestone Steel products are now Accuride
Wheels Henderson Kentucky P.O. BOX 40 ZIP
42420-0040 PH 502 826-5000.
SERIES DESCRIPTION TORQUE
(FT. LBS.)
G20 1/2 In . Bolts (5) 75-100
G-30,
P-20, 30 9/16 In . Bolts (8) 90-120
Single Wheels
9/16 In . Bolts (8) 140
G-, P-30
Dual Wheels Heavy Duty 180 5/8 In. Bolts (10)
SECTION 3
Figure 3-20 -Worn/Cracked Wheels
Cracks running from stud hole to stud hole (Figure 3-20)
on the bolt circle indicate a loose-mounting condition .
Cracks running from hand hole to stud hole, hand hole to
hand hole, or hand hole to rim are a direct result of overloading
. If this type of failure occurs, the position of the
failed wheel on the vehicle should be noted and the actual
working loads of that axle should be checked .
BENT RIM CHECK/TIRE TO RIM MATCHING
STEERING, SUSPENSION, WHEELS AND TIRES
The following procedure can be used to check for a bent
rim or to properly match a tire to a rim .
1 . Mount the suspect wheel end tire assembly on a suitable
fixture such as an off-car wheel balancer or front
spindle of the vehicle .
2. Using a dial indicator, measure the center point of the
tire thread. Mark the high point with chalk (to be used
in Step 4).
NOTE: For this measurement, the tire should be "run"
recently so that it is warm to avoid a false reading
of cord "flattening" which is caused from sitting
stationary.
3. Remove the tire from the rim and measure both the
radial and the lateral runout at the bead area of the
rim as shown in Figure 3-21 . Using chalk, mark the
high point on the radial runout of the rim .
4. Check the runout specifications listed in Figure 3-21 .
If the runout does not exceed the listed specifications,
remount the tire on the rim . Position the high point of
the tire (marked with chalk) OPPOSITE (180 degrees)
from the chalk mark designating the high point of the
rim . This procedure presents the least amount of radial
vibration potential .
5. Balance and remount the wheel and tire assembly on
the vehicle .
MEASURING RADIAL RUNOUT
MAXIMUM WHEEL
RUNOUT SPECIFICATIONS
RADIAL LATERAL
.030" .055"
HIGH SPOTS
1
FA~nn
a"g4 TIRE
WHEEL
jLOW SPOTS
WHEEL
TIRE
MEASURING LATERAL RUNOUT
Figure 3-21- Radial/Lateral Runout Measurement
3- 1 7
SECTION 3
Figure 3-22- Effect of Inflation on Tire Wear
TIRE WEAR
EFFECT OF INFLATION ON TIRE WEAR
Underinflation - This causes tires to flex excessively,
causing heat build-up and increased tire wear (Figure
3-22). Underinflation leads to (1) excessive wear on shoulder
of tread, (2) irregular tread wear, (3) ply separation,
(4) greater susceptibility to bruising, and (5) tread
separation .
STEERING, SUSPENSION, WHEELS AND TIRES
wU
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IL
0
zw
wa
40 60 60 100 120 140
PERCENT OF RECOMMENDED INFLATION
Proper inflation pressures for various tire loads are shown
in Figure 3-17. For maximum tire life, these pressure recommendations
should be followed. Both overinflation and
underinflation can greatly reduce tire life. Likewise, the
life of overloaded tires is shortened considerably . Greatest
tire economy is achieved by selecting tires large enough
to carry maximum loads without overloading, and by adjusting
inflation pressures dpwnward when less than maximum
loads are carried .
Overinflation - This is one of the greatest causes of tire
damage. Overinflation does not add strength to a tire, nor
does it compensate for overloading . Instead, it weakens
the tire and causes more rapid wear (Figure 3-22). Specifically,
overinflation causes (1) rapid wear in center of
tread, (2) greater susceptibility to impact breaks, (3) weakening
of bead, (4) stresses that lead to tread separation,
(5) reduced cushioning, leading to increased truck maintenance
costs, and (6) reduced traction and skid
resistance.
3-113
EFFECT OF OVERLOADING ON TIRE WEAR
Tires that are loaded beyond their maximum-rated carrying
capacity will have their useful life significantly shortened.
As shown in Figure 3-23, tire life decreases rapidly
as overloading increases. For example, it is seen that only
a 10 percent overload reduces tire life by about 15 percent.
An overload of 50 percent reduces tire life by 60 percent.
The dotted line is a projection of the solid curve, obtained
with actual tire experience over a long period of time. The
extreme left end of the solid curve shows that running
tires at less than rated load results in a substantial increase
in tread mileage.
Figure 3-23 - Effect of Overloading on Tire Wear
EFFECT OF OVERHEATING ON TIRES
When a tire gets extremely hot by operating over a considerable
distance in a severely underinflated or flat condition,
or with dragging brakes (these are most common
causes), the internal frictional heat created may build up
to a point where the tire actually bursts into flame . This
usually occurs in a dual assembly where one tire is flat
and the other tire continues to operate in an overloaded
and/or underinflated condition . In such cases, either the
completely flat tire or the tire carrying the load could build
up a sufficiently high temperature to ignite, as shown in
Figure 3-24. Line A of this chart shows time and tire temperature
with a tire operated at proper loading and inflation
pressure. Line B shows a 20 percent overload and/or
underinflation . Note that the tire temperature has moved
into the HOT area of the chart. Line C of the chart reflects
a 40 percent overload and/or underinflation which has
moved into the DANGER area.
00 -
90
60
70
LOSS
TO
OF SERVICE
OVERINFLATION
DUE
50"~ F
40'"
SERVICE
NDERINFLATION
DUE
-_
aoMAN
ZONE-
L
_-
10
0
SECTION 3
w
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C7
2ZZ
W
I--
1 2 3
RUNNING TIME IN HOURS
Figure 3-24- Effects of Time, Temperature and
Pressure on Tire Wear
STEERING, SUSPENSION, WHEELS AND TIRES
NOTE: It is extremely difficult to extinguish a tire fire since
the internal temperature causes repeated ignition .
A fire extinguisher should be used to control the
fire until the tire can be removed from the vehicle .
The best protection against a tire fire is to avoid
running on flats and to check operating pressures
regularly .
Figure 3-25
3-19
REAR WHEEL DRIVE
ALL TIRES OF THE SAME SIZE, TYPE AND LOAD RANGE
o
0 a a D
DUAL REAR
FRONT
C Z7
or,~ 4ca
REAR TIRES DIFFERENT TO FRONT TIRES
BY TYPE, SIZE OR LOAD RANGE
DUAL REAR
FRONT
OO
a00
40% OVERLOAD
LINE
DANGER
20% OVERLOAD
HOT
LINE B
NORMAL RATED
LINE
APPENDIX 3-1
STEERING RELAY AND TIE ROD
PARTS IDENTIFICATION
The following illustration has been extracted from the GM Parts Book. The typical Parts Book illustration shows group
numbers of front-end parts. Major parts numbers have been added for reference.
(1978 AND PRIOR)
GM PART NO.
3956453
GM PART NO.
3956454
1979 TO CURRENT "P(32)" STEERING LINKAGE
3-20
271 N.S . SUPPORT ASM, Strg Relay
1. 6.870 ROD, Strg Relay . . . . . . . . . . . . . . . . 6270303 (See Items 38,39,40,41,42) . . . . . . . . .
2. 6.242 SEAL, Tie Rod Soc Ball Stud . . . . . . . 328144 28. 8.917 NUT (7/16"-14) . . . . . . . . . . . . . . . . . . .
3. 8.984 FITTING, Lug Straight (1/4"-28) . . . . . 29. 8.915 NUT (1/2"-20) . . . . . . . . . . . . . . . . . . .
4. 6.230 ROD, Inr Tie . . . . . . . . . . . . . . . . . . . . 14002550 30. 8.938 PIN, Cotter (3/32" x 1") . . . . . . . . . . .
5. 8.917 NUT (3/8"-16) . . . . . . . . . . . . . . . . . . . 31 . 6.525 COUPLING, W/Flange Kit, Strg Gr . . . 7828871
6. N.S . CLAMP, Adj Tube (Part of #7) . . . . . . 32 . 6.525 BOLT, Strg Shft Cplg
7. 6.232 TUBE UNIT, Tie Rod Adj (3/8"-24 x 1 3/16") . . . . . . . . . . . . . . . . 7807271
(Includes Items 5,6,8) . . . . . . . . . . . . . 12309226 33 . 6.895 ARM, Strg Idler . . . . . . . . . . . . . . . . . . 14013036
8. 8.900 BOLT (3/8"-16 x 1 5/8") . . . . . . . . . . . 34 . 6.897 WASHER, Strg Idler
9. 6.233 ROD, Otr Tie . . . . . . . . . . . . . . . . . . . . 458201 Shk Abs Grommet . . . . . . . . . . . . . . . . 3798007
10. 8.938 PIN, Cotter (1/8" x 1 1/4") . . . . . . . . . 35 . 8.915 NUT (3/8"-24) . . . . . . . . . . . . . . . . . . .
11 . 6.164 NUT, Strg Link . . . . . . . . . . . . . . . . . . . 3983037 36 . 7.244 GROMMET, Spl
12 . 8.938 PIN, Cotter (1/8" x 1 1/4") . . . . . . . . . (1 7/32" OD 7/8" Thk) . . . . . . . . . . . . . 6270752
13 . 8.917 NUT (5/8"-18) . . . . . . . . . . . . . . . . . . 37 . 6.895 ABSORBER, Strg Relay
14. 6.895 ARM, Strg Relay and Conn Rod . 14013037 and Tie Rod Shk . . . . . . . . . . . . . . . . . 22011982
15 . 8.916 NUJ' (3/4"-16) . . . . . . . . . . . . . . . . . : . 38 . 6.896 SUPPORT, WBushings Strg Rly
16 . 8.931 WASHER (3/4") . . . . . . . . . . . . . . . . . . & Conn (Includes Item 39) . . . . . . . . . 3941739
17 . 6.870 ROD, Strg Conn . . . . . . . . . . . . . . . . . 6271489 39 . 6.896 BUSHING, Strg Rly &Conn Rod
18 . 6.859 ARM, Pitman . . . . . . . . . . . . . . . . . . . . 6259993 Supt Shf (Included in item 38) . . . . . . 266316
19 . 6.861 WASHER (1 1/2" OD 7/8 ID) . . . . . . . 40 . 6.896 SHAFT, Strg Rly &
20 . 6.861 NUT (7/8"-14) . . . . . . . . . . . . . . . . . . . 5667628 Conn Rod Arm Supt . . . . . . . . . . . . . . 3768940
21 . 6.508 GEAR, Strg('1) . . . . . . . .. . . . . . . . . . . 7834511 41 . 6.897 NUT, Strg Rly &
22 . 6.898 SEAL, Strg Conn Rod BalStud . . . . . 3865608 Conn Rod Arm Supt Plug . . . . . . . . . . 3768947
23 . 8.984 FITTING, Lug Straight (1/8"-17) . . . . . 42. 6.897 PLUG, Strg Rly &
24 . 6.898 SEAL, Strg Lnkg Piv Shf . . . . . . . . . . . 3786454 Conn Rod Arm Supt . . . . . . . . . . . . . . 3768945
25 . 8.900 BOLT (7/16"-14 x 1 3/4") . . . . . . . . . . . NOTE 1 : For information on serviceable components refer to
26 . 8.929 WASHER (7/16") . . . . . . . . . . . . . . . . . applicable Assembly illustration .
APPENDIX 3-2
TYPICAL LOAD HEIGHT CURVES
-MOTOR NOME
The following Load Height Curves have been extracted from the 1987 Chevrolet Commercial and Truck Chassis Body
Builders Book showing Spring Number and Spring Charts for P-Series Motor Home units. As shown on the following
charts, known weights compared to actual "A/BC"'` or "D" dimensions can determine if the spring is performing
according to its rating . Actual measurements will be ± 1/2-inch on the chart and normally considered within the spring
makers production capability. At or near maximum ratings, most GM leaf springs are designed to be in a slight reverse
arch. Check with your local Chevrolet Branch Office Truck Department for Spring Charts for other years and models.
'` Depending upon reference sources, this dimension is referred to as either an "A" dimension or a "BC" dimension.
For the purposes of this manual, both dimensions have been included to aid the motor home owner in the determination
of spring ratings .
JuJ
QH
uj
0Cn
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ZU
OZ
u_
Ua
6
5
4
3
2
0
1000
NOTE: This chart is for the typical P-Series Motor Home.
Additional model information is available in the
Body Builders Book.
2000 3000 4000 5000 6000 7000 8000 9000
LOAD SHOWN IS TOTAL AXLE LOAD AT GROUND-FRONT
(POUNDS)
Figure A3-2-1- Load Height Curve "A/BC" Dimension - Motor Home
NOTE : 1984 to Current- A front spring with GM Part No . 14054345 can be used for 1983 and prior years that
require a front spring with GM Part No. 472222. This will raise the front of the vehicle
3/8 inch to 1/2 inch measured at the "A/BC" measurement location shown in the chart
above.
3-21
472222 = 3,750 LBS. SQUEEZE FORCE
14054345 = 4,190 LBS. SQUEEZE FORCE.
WITH PLASTIC AIRBAGS Fv (14054345)
"'A/BC :" FRONT SUSPENSION
CROSS MEMBER FLANGE T6
LOWER CONTROL ARM SPRING RATING
BRACKET MUST BE MEASURED
PERPENDICULAR TO
CROSS MEMBER FLANGE.
MEASUREMENT IS "IRON TO
IRON." RUBBER BUMPER IS
D (P30032) DUAL YD8/F66
WITH PLASTIC AIRBAGS w
APPENDIX 3-2
TYPICAL LOAD HEIGHT CURVES
-MOTOR NOME (Cont'd)
NOTE: This chart is for the typical P-Series Motor Home .
Additional model information is available in the
Body Builders Book.
w
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ILL
I1
O
OHHOm
O a
ww
D
U
~- z
LLJ
XQDQwD
ILL O
O
7
6
5
4
3
2
2000 3000 4000 5000 6000 7000 8000 9000 10000 11000
LOAD SHOWN IS TOTAL AXLE LOAD AT GROUND-REAR
(POUNDS)
Figure A3-2-2- Load Height Curve "D" Dimension- Motor Home
8# P31432Y88 H D. DUALS
7#
P30
P30832 YD9 DUALS P31832 Y138 H.D . DUALS
32 YD9 DUALS (15599376)
(P31432 YD9 DUALS 5000 lbs. each 10,000 total
5599368) 10 leaf 56 by 2.50 by 4.04 (hick
3100 lbs. each 6200 total
7 leaf 52 by 2.50 by 2.66 thick
9# P30832 G50 DUALS
P31132 G50 DUALS
P31432 G50 DUALS
3750 lbs. each 7500 tota
8 leaf 52 by 2 .50 by 2 .97 1thick
D:TOP F AXLE
TUBE T -
OF FRA
`S
I I
1AA
SPRING RATING
I
qN801h,
SECTION 4-PROPELLER SHAFTS AND UNIVERSAL JOINTS
PROPELLER, SHAFTS AND
UNIVERSAL JOINTS
GENERAL DESCRIPTION
PROPELLER SHAFTS
The propeller shaft is a steel tube which is used to transmit
power from the transmission output shaft to the differential
. To accommodate various model, wheelbase and
transmission combinations, drive shafts differ in length,
diameter and the type of splined yoke. Each shaft is installed
in the same manner. A universal joint and splined
slip yoke are located at the transmission rear extension.
The slip yoke permits fore and aft movement of the drive
shaft as the differential assembly moves up and down.
The spline is lubricated internally by transmission lubricant
or grease. An oil seal at the transmission prevents leakage
and protects the slip yoke from dust, dirt and other harmful
materials . (See Figure 4-1 .)
Since the drive shaft is a balanced unit, it should be kept
completely free of undercoating and other foreign material
which would upset shaft balance .
Both one-piece, two-piece and three-piece propeller
shafts are used depending on the model .
On models that use a two-piece shaft, a three-piece or
more shaft, the shaft is supported near its splined end in
a rubber-cushioned ball bearing, commonly referred to as Figure 4-2- Universal Joint-Exploded View
NOTE: Single exhaust requires only 1 shield .
DIFFERENTIAL
UNIVERSAL JOINTS
BEARING SUPPORT
(CENTER)
TRANSMISSION
UNIVERSAL JOINT
BEARING HEAT SHIELD
15680325
1985-1994
Figure 4-1 -Propeller Shaft
the center bearing, which is mounted in a bracket attached
to a frame cross member. The center bearing is permanently
lubricated and sealed.
UNIVERSAL JOINTS
The simple universal joint is basically two Y-shaped yokes
connected by a cross member called a spider. The spider
is shaped like an "X", and arms that extend from it are
called trunnions. (See Figure 4-2.) The spider allows the
two yoke shafts to operate at an angle to each other.
SECTION 4
MAINTENANCE AND INSPECTION
PROPELLER SHAFTS AND UNIVERSAL JOINTS
Generally, the propeller shaft and universal joints require
little maintenance. Periodic inspection is recommended,
however, for proper propeller shaft balance and universal
joint lubrication . If area around caps appears to be excessively
dry, it may indicate a need for bearing relubrication
or universal joint replacement. (See Figure 4-2 .) A
failing universal joint often squeaks on start-up or "klunks"
with direction change.
If the center bearing is replaced, the bearing itself does
not need to be packed with grease. However, chassis
lubricant should be packed within the dust shields to form
a dam to aid in preventing water and dirt from reaching
the bearing. The dust shields are staked into position following
the procedure detailed in the shop manual. (See
Figure 4-3.) Typical U-joint and slip spline failures are
shown in Figure 4-4.
Figure 4-4- Typical Failures- U-Joints and Slip Spline
Figure 4-3 - Center Bearing
LACK OF LUBRICATION
BRINNELLING
END GALLING
SLIP SPLINE GALLING
SECTION 4
DRIVELINE NOISE AND/OR VIBRATION
CHECKS
The following information is presented as an aid to the
motor home owner as diagnostic "thought-starters" and
are listed as possible causes for driveline noise and/or
vibrations. As applicable, references are made to those
areas of this manual providing additional information .
CHECK IF:
PROPELLER SHAFTS AND UNIVERSAL JOINTS
" Drivelines are out of static and dynamic balance. See
Driveline Balance Procedure section of this manual.
" Crosses in the universal joints are worn or damaged .
See Figure 4-4 in this section of the manual.
" Center bearing is worn or loose. See Figure 4-3 in this
section of the manual.
" Teeth on the ring and pinion gear of the driving axle
are worn or pitted .
" Spring U-bolts are loose.
" Parking brake drum is warped and/or out of balance.
See Figure 6-5 of this manual.
Tires -wheels are out of balance .
Difference in angular velocity of universal joints results
from incorrect joint working angles. See Appendix 4-1
and Appendix 4-2 at the end of this section of the
manual.
" Propeller shaft joints are out of phase on one or more
splines . See Appendix 4-1/Figure A4-1-4 or Appendix
4-2/Figure A4-2-6 at the end of this section of the
manual .
" Propeller shaft does not extend far enough into the slip
joint. Propeller shaft should extend into the slip joint
2/3 to 3/4 of the spline length . This should not be less
than 2-1/2 inches in length .
" Weld at the seam of the drive tube running the length
of the drive tube is cracked or there is a cracked weld
where the U-joint attaches to the propeller tube.
" U-joint has a missing needle bearing . This situation
usually creates a "snapping" noise under load as the
needles straighten under load. See Figure 4-2 in this
section of the manual.
" Transmission rear support mount worn .
Engine block motor mounts worn.
DRIVELINE BALANCE PROCEDURE
Each piece of a driveline propeller shaft is manufactured
to be in "balance" by itself. However, there are times when
assembly of two or more shafts together creates an undesirable
running combination.
The following drive shaft balance procedure can be applied
to a motor home and the procedure can be performed
on the shop floor. The wheels should be blocked
and both axle shafts should be removed to prevent
any possibility of spider gear spin-out during the
balancing process. The procedure requires the
service technician to place four chalk marks (numbers 1
through 4) on the propeller shaft. (See Figure 4-5 and
Figure 4-6.)
Figure 4-5 - Chalk Reference Marks on Propeller
Shaft
ROTATE CLAMP HEADS
AWAY FROM EACH OTHER
Figure 4-6 - Balance Hose Clamps in Position
SECTION 4
Run the engine and drive shaft speed up to the point
vibration is felt and note the speed showing on the speedometer.
Also, note the "intensity" of the vibration . STOP
THE ENGINE AND DRIVE SHAFT. Install a hose clamp
and position the screw pointing toward one of the chalk
reference marks. (See Figures 4-5 and 4-6.) Retest for
vibration and note any gain or loss in vibration disturbance.
A single hose clamp will usually increase or reduce
the vehicle vibration by feel . The screw portion of the hose
clamp is the weight being moved around the shaft.
A wheel balancer with a strobe light helps facilitate the
balancing of the propeller shaft. The strobe light shows
the amount of weight that is needed and the exact location
where the weight is needed . However, human touch on
a cross member, pinion nose, or transmission extension
housing can be very helpful in combination with the strobe
light.
1 . Block the wheels and remove both axle shafts .
2. Mark and number the drive shaft at four points 90
degrees apart around each shaft just forward of the
balance weights. (See Figure 4-5.)
3. Place the strobe light wheel balancer pick-up unit
directly under the differential pinion nose as far as
possible. (See Figure 4-7.) Repeat this step at each
carrier bearing support (for two, three or more drive
shaft units) .
4. With the vehicle running in gear at the vehicle speed
where the disturbance is at its peak, allow the driveline
to stabilize by holding a constant speed. Point
the strobe light at the spinning shaft and note the
position of one of the numbers on the shaft.
CAUTION : NEVER RUN THE, VEHICLE HIGHER THAN
60 MPH. ALL PERSONNEL MUST STAND CLEAR OF
THE U-JOINT AND BALANCE WEIGHT AREA AS SERIOUS
INJURY MAY RESULT.
5. Shut off the engine. Allow the shaft to stop, then manually
turn the shaft until the chalk numbers are in the
same position as shown by the strobe light.
PROPELLER SHAFTS AND UNIVERSAL JOINTS
Figure 4-7 - Strobe Light Wheel Balancer Pick-up
Unit
4-4
6. Install two hose clamps on the drive shaft as close
to the rear of the drive shaft as possible, as shown
in Figure 4-6. Position both screw clamp heads 180
degrees from the heavy point of the shaft as shown
by the strobe light. (See Figure 4-8.) Tighten clamps.
NOTE: When the strobe light flashed, the heavy point of
the shaft was down at the bottom 6 o'clock position
. To balance the drive shaft, it is necessary
to position both clamp heads 180 degrees from
the heaviest point, or at the top of the shaft in the
12 o'clock position.
7. Run the vehicle through the speed range of the disturbance.
If the problem is eliminated go to Step 9.
If the disturbance is not gone and the strobe light
shows the clamp heads at the bottom (6 o'clock position)
of the shaft, go to Step 8.
a. If the strobe light shows the two clamp heads at
the top of the shaft, add one more hose clamp to
the shaft and recheck. If the strobe light still shows
the three clamp heads at the top (12 o'clock position)
of the shaft, remove the shaft and reinstall
it 180 degrees on the rear flange. Recheck the
balance without any clamps. If the disturbance is
gone, proceed to Step 9. If the disturbance is not
gone, repeat the balance procedure beginning
with Step 6 .
b. Generally if more than three hose clamps are
needed, the shaft should be replaced unless the
hose clamps are positioned opposite the weldedon
factory weight. This position of the clamps
would indicate that the factory weight position is
counter productive in the original position . If the
hose clamps are positioned opposite the factory
weight, knock off the factory weight and rebalance
the shaft beginning with Step 6.
However, if the clamps are also 180 degrees from
their original position after the shaft was rotated 180
degrees, the drive companion flange on the axle is
out of balance and must be replaced .
8. Rotate two of the hose clamps equally away from
each other toward the top (one each way from the
original position as shown in Figure 4-8) in small
amounts until you find the best possible balanced
condition . In some cases, it may be necessary to use
one clamp or possibly as many as three clamps to
obtain a proper balance.
NOTE: It may be necessary to repeat these procedures
at each cross member carrier bearing with the
strobe pick-up contacting the nonmoving metal
bearing retainer or against the cross member as
close to the bearing as practical.
SECTION 4 PROPELLER SHAFTS AND UNIVERSAL JOINTS
9. Install the axle shafts and road test the vehicle for
final check of balance.
NOTE: Vibration felt in the vehicle in the repair stall may
not be felt by the driver under road conditions.
Figure 4-8- Hose Clamp Positions to Balance Shaft
NOTE: Many years of engineering and testing are used to develop your motor home chassis for a smooth ride
and handling . '
Many units are modified by stretching or shortening of the wheelbase to match the style and/or length
of the body by the coach builder.
This requires the frame and drive shafts to be cut and some length removed or added which is a long
standing practice and does not create any problems if properly reengineered and assembled.
However, many times, vibrations are created because the drive shafts and shaft hangers were not properly
realigned or rebalanced before delivery . Other times, vibrations and/or damage are caused when
different types of rear suspension and/or tag axles (non GM)are installed by either the coach company
or later by the owner of the coach.
Alterations and/or such modifications noted above which create an owner concern or damage to the
coach, are the responsibility of the company or the persons altering the chassis components after
final assembly by General Motors .
10.;, After final check, drill a 1/8-inch hole through each
clamp and drive shaft and install a pop rivet to prevent
slip or tampering.
STEP 1 STEP 2 STEP 3
DETERMINE POINT ADD HOSE CLAMPS 180° ROTATE TWO CLAMPS EQUALLY
OF UNBALANCE FROM POINT OF UNBALANCE AWAY FROM EACH OTHER
UNTIL THEY BECOME UNTIL BEST BALANCE
HEAVY SPOT IS ACHIEVED
DRIVELINE VIBRATIONS-ONE
AND TWO DRIVE SHAFT
SYSTEMS
The following information is directed to service personnel
andis presented as an aid to the motor home owner in understanding
driveline vibrations (as driveline vibration
problems are often not recognized by the owner).
Driveline vibrations will generally be a high-speed vibration
or a "buzz" at drive shaft speed compared to wheel
and tire vibration that is a much slower speed . Standard
factory units normally do not have problems unless the
assembler in production has installed the incorrect length
hanger bearing support or some part is off in design specification
. The units most likely to have vibration problems
are modified units where a wheelbase is changed, a drive
shaft added or a change that has occurred when the suspension
has been modified or changed (for example, a
spring changed or after-market suspension installed replacing
production springs) .
On some units that have operated in a heavy-loaded condition,
the last shaft and pinion nose will change enough
to require a driveline and/or pinion nose change. The following
information should be read by service personnel
and understood as a guideline for alignment procedures.
NOTE: Motor homes produced with a wheelbase larger
than 178 inches will have three drive shafts .
The following driveline rules are for one and two drive
shaft systems . '
Rule Number 1 -The working angles of each pair of Ujoints
must be within one-half degree of being equal on
shafts that turn at 3,200 RPM or higher, or within one
degree of being equal on shafts that turn at speeds below
3,200 RPM.
Rule Number 2 - (Involves a two drive shaft, three Ujoint
system.) With a three-joint system there is always an
odd joint that cannot be'paired with another joint. Since
the U-joint between the transmission and the front shaft
does not have a mate to cancel out its acceleration and
deceleration, the front shaft should be within one-half degree
of the transmission angle for high-speed shafts and
within one degree for low-speed shafts . If the rear-end
pinion angle is not equal to either the engine/transmission
angle or front shaft angle, it should be at an angle between
those two. There can be one-half degree difference between
the center and rear U-joint working angles provided
neither of the working angles exceeds 4 degrees on highspeed
shafts, or 5 degrees on low-speed shafts .
The following is an actual driveline case study of an Struck.
The purpose of this example is to indicate that driveline
problems are not restricted to large trucks .
APPENDIX 4-1
4-6
Figure A4-1-1 - Driveline Vibration - Case Study
Example No. 1
NOTE: The angles shown in Figure A4-1-1 were taken
with a very accurate digital protractor and dramatically
indicates an ability to work in extremely
small figures .
In the example (Figure A4-1-1) note that the working angle
between the engine and the first shaft of .44 degrees is
well within the driveline rules. The first joint does not present
any problems. With a .44-degree working angle and
no mating joint, a vibration will never be felt. At the back
two U- joints, the intent is to make a canceling pair within
one-half degree working angle. As shown in the example,
this is very poor; 1 .54 degrees minus .18 degrees equals
a 1 .36-degree difference - clearly beyond the one-half
degree rule.
However, examine what would happen if a one-degree
caster wedge were installed to tip the pinion nose up to
more closely follow the rule of setting the pinion to be
"equal to the transmission angle or front-shaft angle or
an angle between the two."
Figure A4-1-2 -
The example shows quite an improvement . Note that the
two rear joints are canceling within the one-half degree
rule. Another point learned in this case study concerns
the use of the protractor. A one-degree shim was sent for,
which was cast one degree but when installed turned out
to be 1 .26 degrees.
Another move that would seem to defy one of the driveline
rules can sometimes be done on light-duty applications .
This involves (through design considerations) keeping the
pinion nose as low as possible to help reduce driveline
tunnel size and the hump that is needed in the trunk floor
for axle clearance .
Driveline Vibration - Case Study-
Example No. 2
DRIVELINE VIBRATIONS-ONE
AND TWO DRIVE SHAFT
SYSTEMS (Cont1d),
Note the result shown in the case study example (see
Figure A4-1- 3) of reversing the shim and tipping the pinion
nose down by one plus degree.
Figure A4-1-3- Driveline Vibration- Case Study-
Example No. 3
As a result, you end up with even smaller working angles
but still within the one-half degree cancellation. of Rule
Number 1 . This illustrates two very proper approaches to
driveline correction (but still returning to the key point of
joint working angles canceling in pairs and within one-half
degree).
MAKE SURE THE YOKES ON EACH
SHAFT ARE PARALLEL
Using a magnetic base dial indicator,
perform a radial runout
check of the shaft . Readings at
each location shown must be
within limits given.
MAXIMUM RUNOUT
.005" .015" .010" .015"
rrn r
3" I hI
CENTER
OF SHAFT
FigureA4-1-4- Proper Phasing and Maximum Drive Shaft Runout
The following examples demonstrate acceptable driveline the one common factor among the various combinations
combinations and are presented as an aid in reempha- - the joint working angles are equal as a pair and qualify
sizing the simple single drive shaft two-joint system. Note under Rule Number 1 .
.0 -IL3.0
+4.0
,-4,0 `r U +30
-- 0
4-5.0 0
+30
3.0 l,
+ 2 .0 .1-1 _+5.0
APPENDIX 4-1
Figure A4-1-5-Acceptable Driveline Combinations
4-7
Before completing a discussion of two-shaft drivelines,
consider the following : "Could the system be reversed
and the one-half degree be placed at the pinion end?"
The answer is a technical yes, but in reality, you are better
off with the half degree at the engine end. With the solidmount
transmission and first shaft, you are generally better
off to have your bigger working angles further from the
passenger compartment at the pinion end. Noise and vibrations
are further away and are somewhat absorbed in
springs and suspension . Concerning this, consider what
happens to the angles of the middle joint and at the pinion
nose as the axle and the drive shaft move through loadings
and ride travel. Chances are small of maintaining
proper joint relationships. Stay with the one-half degree
at the engine, and equal and canceling angles as a pair
at the middle joint and pinion joint. Also, remember with
a two-shaft system, that the drivelines must be in proper
phase at the slip yoke. If off one spline, a vibration complaint
will result. The illustrations of Figure A4-1-4 show
proper phasing and maximum drive shaft runout.
DRIVELINE VIBRATIONSTHREE"
SFIAFT DRIVELINES
The following information is addressed to service personnel and is presented as an aid to the motor home owner in
understanding the three-shaft drivelines typical of RV vehicles and farm trucks . Three-shaft drivelines are perhaps the
simplest and mostinteresting of all drivelines because of the many and varied combinations possible.
The following are several basic rules:
Rule Number 1 - The working angle of each pair of Ujoints
must be within one-half degree of being equal on
shafts that turn at 3,200 RPM or higher, or within one
degree of being equal on shafts that turn at speeds below
3,200 RPM. No working angle shall exceed four degrees
on high-speed shafts, or five degrees on low-speed shafts .
(This is essentially the same rule as found in single and
two drive shaft systems .)
Rule Number 2 - (The concept of the broken back angle
.) The first shaft angle plus the third shaft angle is
divided by two and equals the second shaft angle. For
example: A first shaft of zero degrees plus the third shaft
of 90 degrees equals 90 degrees divided by two equals
45 degrees as the proper setting for the second or middle
shaft.
Rule Number 3 - When computing working angles, two
components that are tilted in the same direction are subtracted
from each other. When connecting components
are not in the same direction, such as a positive and a
negative angle, the angles are added to determine the
working angle.
Figure A4-2-1 - Driveline Vibrations -Truck Case
Study- Example No. 1
Examine the truck case study shown in Figure A4-2-1 . To
better understand the truck case study, draw a line vertically
down through the middle drive shaft. You will find
that you are really working with two trucks with single drive
shafts . As you apply Rule Number 1, you will notice that
there is not a problem with the rear pair of joints, but the
front half of the truck, with three degrees of working angle
and zero degrees for its mating joint, presents a problem.
With single-shaft drivelines, one method to employ would
be to align the shafts so the shafts operate in parallel
planes, but at different levels. (See Figure A4-2-2.) For
example : Lower the second shaft to six degrees, and by
installing a caster wedge, tip the pinion nose up slightly
to six degrees .
APPENDIX 4-2
4-8
Figure A4-2-2 - Driveline Vibrations- Truck Case
Study- Example No. 2
The above example shows equal canceling angles. However,
the back pair exceed the four-degree maximum
working angle of Rule Number 1 . Note the last shaft is
negative (uphill to the pinion) . Negative shafts are added
to positive shafts .
The following chart shows the relationship of shaft speed
to maximum allowable working angle.
Figure A4-2-3- Shaft Speed To Maximum Working
Angle
In the above truck case study, the requirement was to
raise the driveline system to eliminate the negative last
shaft running uphill to the pinion . This situation created
working angles that were too large. In this case study
example, the broken back angle becomes an advantage
and drastically reduces work in the process . (The original
example shown in Figure A4-2-1 had the pinion nose at
two and one-half degrees and the center shaft at three
degrees.)
Using Rule Number 2, the following presents a case study
example of a broken back angle out of the front of the
truck. With the engine as the first shaft, and the middle
drive shaft considered as the third shaft, determine the
shaft setting for the second shaft. Use two and one-half
degrees for the third shaft.
RPM Max working angle RPM Max working angle
5000 3°15" 3000 5' 5"
4500 3°40" 2500 7o 0"
4000 4 0 15 " 2000 8 ° 40"
3500 50 0" 1500 11°30"
6 degrees as the first shaft
2 1/2 degrees as the third shaft
8 1/2 degrees divided by two equals
4 1/4 degrees second shaft
Figure A4-2-4 - Drivellne Vibrations -Truck Case
Study- Example No. 3
The following shows a broken back angle installed in the
front half of the truck case study example.
APPENDIX 4.2
DRIVELINE VIBRATIONSTHREE"
SNAFT DRIVELINES
(Cont1d)
Note that by picking the middle shaft to be the same as
the pinion, you have corrected the rear of the truck to near
ideal cancellation, as well as correcting the front of the
truck. Changing hanging bearing length is generally a cutand-
weld as an overlap to shorten a hanger, or fabricating
a spacer block. (You must locally obtain longer bolts to
make a longer hanger.) Almost everything that applies to
single-shaft systems applies to three-shaft trucks. Even
the broken back angle can occasionally be used in some
specialized single-shaft trucks, such as airport luggage
toters where the rear axle is moved forward almost under
the driver's seat. With a very short drive shaft, parallel
alignment would make working angles too large. In the
toter, the pinion becomes the third shaft and the engine
is the first shaft. The manufacturer may install a broken
back to obtain equal working angles at the transmission
and the pinion, and reduce working angles in the process.
It is also important, as in the two drive shaft truck, to have
the last drive shaft properly phased on the slip spline .
Make certain the fixed yoke and the splined yoke are in
the same plane. If they are off even one spline, a vibration
complaint may result. The illustrations below (see Figure
Figure A4-2-5 - Driveline Vibrations -Truck Case A4-2-6) show proper phasing and maximum drive shaft
Study= Example No. 4 runout.
MAKE SURE THE YOKES ON EACH
SHAFT ARE PARALLEL
Using a magnetic base dial indicator,
perform a radial runout
check of the shaft. Readings at
each location shown must be
within limits given .
MAXIMUM RUNOUT
.005" .015" 0.10" .015"
CENTER
OF SHAFT
Figure A4-2-6 - Proper Phasing and Maximum Drive Shaft Runout
GENERAL DESCRIPTION
The rear axle assembly consists of the drive pinion, ring
gear, differential and axle shafts in one housing . The drive
pinion transfers power input from the propeller shaft to
the ring gear which drives the axle shafts and rear wheels .
The ring gear is a reduction gear which lowers the speed
(RPM) of the propeller shaft to a speed which is usable
for driving the rear wheels.
MAINTENANCE AND INSPECTION
DIFFERENTIAL FLUID
The differential requires little maintenance ; however,
periodic fluid level checks are recommended to ensure
smooth operation. In addition, the fluid should be changed
in accordance with the time and mileage intervals listed
in the Maintenance Schedule for the vehicle .
To check differential fluid level, remove the plug, as shown
in Figure 5-1 . If the fluid level is sufficient, fluid will seep
out of the opening . If it doesn't, add the necessary amount.
Replace the plug, making sure it is properly seated.
Figure 5-1 - Rear Axle Lubricant Fill Hole
Normal operating temperature of rear axles and manual
gear-shifting transmissions is about 1'00 degrees above
ambient temperature. Both units are cooled by lube oil.
The tube oil carries heat from the friction points to the
case where the heat is dissipated into the air flowing past
the case. The following are typical examples of overheat
possibilities . Overheating can be caused by the :
" Housing severely coated with dirt or dried mud which
acts as an insulator holding heat in the housing.
" Differential operated with low 'lubricant levels due to
leaks.
" Incorrect or mixed lubricant brands which foam and
reduce heat transfer.
SECTION 5-REAR AXLE
REAR AXLE
" Engine exhaust positioned too close to the transmission
or a pipe leak directing heat on the differential .
" Break-in lubricant not drained quickly enough after
being subjected to high break-in temperatures thereby
destroying the lubrication additives .
" OVERLOADS-Overloads tend to reduce road speeds
and cause the vehicle to be operated in lower gears for
extended periods of time. This increases heat in the
engine, transmission, drive-line universal joints and rear
axles.
HIGH SPEED OPERATIONS-Very high speeds tend
to churn the lubricants to the point that aeration occurs.
Lube oil filled with air bubbles cannot carry the heat
away from its point of origin to the housings where it
can be dissipated into the air stream .
" Extended period of time between lube oil changes. The
additives contained in lube oils do wear out on a slow
and gradual basis. As the additives wear out, the viscosity
may change and the lubricating qualities are depleted.
Additionally, the metals content (that occurs
under normal wear) increases in the gear oil . As this
process continues, temperatures and friction increase
within the component until a failure occurs.
NOTE: Many large fleet operators have the lubricants
that are drained from their vehicles analyzed to
determine if the change frequency can be in
creased or must be decreased. For the individual
owner the results of this lubricant analysis may
not justify the expense. The individual owner may
find that the best method to follow is to drain the
fluid every fourth oil change and refill, to check
the fluid level and add fluid as needed at every
oil change, and in dusty areas or trailer towing
applications, to drain the fluid at every oil change
and refill . A large loss of fluid in this system may
indicate a problem. Have the system inspected
and repaired at once to avoid further damage.
WHEEL BEARING ADJUSTMENT (TAPERED
BEARING)
Before checking bearing adjustment, make sure the
brakes are fully released and do not drag.
NOTE : With any floating axle, wheel bearing lubrication
is normally supplied by the gear oil in the axle.
Anytime the wheel bearings are replaced or re
moved for inspection, it is a good practice to pack
the bearings with high temperature wheel bearing
grease (GM Part No. 1051344) . The grease packing
assures ample initial lubrication . As the rear
axle gear oil works its way to the wheel bearings,
the grease packing dissolves and is washed away
with the gear oil.
Figure 5-2 - Wheel Bearing Adjustment Specifications
Check bearing play by grasping the tire at the top and
pulling back and forth, or by using a pry bar under the
tire. If bearings are properly adjusted, movement of the
brake drum in relation to the brake flange plate will be
barely noticeable and the wheel will turn freely: If movement
is excessive, adjust the bearing as follows :
1 . Remove the axle shaft and raise vehicle until the wheel
is free to rotate .
2. Keyways and threads on the tube and nut must be
clean and free from chips, burrs and shavings.
3. Disengage. tang of the retainer and remove retainer
from the axle housing tube.
4. Torque the adjusting nut to 50 ft. lbs., while at the same
time rotating the hub assembly and making sure the
bearing cones are seated and in contact with the spindle
shoulder. r
Proper wheel bearing adjustment can be made using a
spanner wrench (GM Tool J-2222-L or equivalent) .
5. Back off nut until loose. Refer to Figure 5-2 for
specifications .
6. If adjusting nut slot is in alignment with keyway in the
axle spindle, insert the square key into slot. If the adjusting
nut slot is not aligned, back off nut a slight
amount and insert the square key into the slot. Do not
back off more than one slot to align the key.
SECTION 5-REAR AXLE
5-2
7. Assemble the snap ring at the end of the spindle to
retain the key in position .
WHEEL BEARING ADJUSTMENT (BARRELTYPE
BEARING)
Before checking bearing adjustment, make sure brakes
are fully released and do not drag .
NOTE: With any floating axle, wheel bearing lubrication
is normally supplied by the gear oil in the axle.
Anytime the wheel bearings are replaced or re
moved for inspection, it is a good practice to pack
the bearings with high temperature wheel bearing
grease (GM Part No. 1051344) . The grease packing
assures ample initial lubrication . As the rear
axle gear oil works its way to the wheel bearings,
the grease packing dissolves and is washed away
with the gear oil.
Check bearing play by grasping tire at, top and pulling
back and forth, or by using a pry bar under tire. If bearings
are properly adjusted, (installed with slight preload), there
will be no movement of the brake rotor and the wheel will
turn freely. If there is movement, adjust bearings by using
the following procedure :
MODEL SOURCE TYPE/CAPACITY RING GEAR SIZE (In.)
P30 . Chevrolet Dana
Chevrolet-Saginaw
Dana 70 #10,000
Dana 80 #10,500
Saginaw #10,000
10-1/2
11 .3
10-1/2
P30 (With H22/H23) Rockwell Banjo/11,000# 12
G30 Chevrolet Salisbury/5700# 10-1/2
G30 (Dual Wheel) Dana Salisbury/6200# 9-3/4
G30 (Dual Wheel) Dana Salisburyf7500# 10-1/2
REAR WHEEL BEARING ADJUSTMENT SPECIFICATION
RING
GEAR
SIZE
(In.)
BEARING
ADJUSTING
NUT TORQUE
(Ft. Lbs.)*
ADJUSTING
NUT
BACK-OFF*
OUTER
LOCKNUT
TORQUE
(Ft. Lbs.)
RESULTING
BEARING
ADJUSTMENT
(In.)
TYPE
OF
BEARING
10-1/2 & 11 50 *' 65 .001 TO .010 TAPERED
9-3/4 50 ** 65 END PLAY ROLLER
12 90 1/8* 250 SLIGHT
PRELOADED
BARREL
ROLLER
~ **Back off nut and retighten to 35 Ft. Lbs. then, back off 1/4 turn . *With wheel rotating .
1 . Remove axle shaft and raise vehicle until wheel is free
to rotate .
2. Disengage tang of retainer from locknut and remove
both locknut and retainer from axle housing tube, with
GM Tool J-25510 or equivalent.
3. Tighten inner adjusting nut (using GM Tool J-25510 or
equivalent) to 90 ft. lbs. torque while rotating wheel
hub at the same time to make sure all bearing surfaces
are in contact . Then back off inner nut 1/8 turn while
rotating wheel. The wheel should turn freely.
4. Install tanged retainer against the inner adjusting nut .
Align inner adjusting nut so short tang of retainer will
engage nearest slot on inner adjusting nut .
5 . Install outer locknut and tighten to correct specified
torque (250 ft. lbs.). Then bend long tang of retainer
into slot of outer nut.
AXLE HOUSING
A gear set operated at its capacity rating will give 100
percent of rated life. Taking the same gear set and reducing
the work load will give a very large gain in life.
Overloading by even very small percentages causes a
very serious loss in life. Overloading also tells a major
story on increased tire wear, wheel bearing and axle housing
failures.
The graph shown in Figure 5-3 (provided by Eaton Axle
Division) indicates the approximate percentage of life expectancy
of axle gear sets and other axle parts. The figures
are based upon dynamometer tests (conducted by
Eaton Axle Division) and are the direct result of accurately
simulated load conditions.
SECTION 5-REAR AXLE
NOTE: A gear set operated at its capacity rating will give
100 percent of rated life. Figure 5-4- Bent Axle Housing
Gross
Combination
Welgid (6CWI
In Pounds
under 45,000
50 .000
Rattaeed 55 .000
81%(of capacity) 300% of Normal Life
90%
100% - Normal L8e
160% of Normal Life
Figure 5-3 - Average Life of Overloaded and
Underloaded Gears
BENT AXLE HOUSING
Overloads destroy axle housings and flexed housings
tend to excessively load inner dual tire. Overloaded wheel
bearings fail earlier than normal. Check for any grease
lube leaks at the bottom of the axle housing. A split gasket
(shown as the shaded area in Figure 5-4) almost always
indicates an overload, or flex and housing distortion, which
destroys the gasket between the carrier and the housing.
NOTE: An overloaded (bent) axle housing
will tend to wear the inner dual tires.
60 .000 109% 160% of Normal Life
65 .000 118% 36% of Normal Life
70 .000 127% 24% of Normal Lilt
1
Over 75 .000 136% 18% of Normal Life
J
GENERAL DESCRIPTION
There are two brake systems on the motor home, the
service brakes and the parking brakes.
The service brakes use hydraulic pressure from a footpedal-
operated master cylinder to actuate cylinders which
apply the brakes at each wheel. Fluid lines and hoses
connect the master cylinder with each of the wheel cylinders.
When the brake pedal is depressed, force is transferred
through the pushrod to the master cylinder primary
piston, which moves forward. Under normal conditions,
the combination of hydraulic pressure and the force of the
primary piston spring moves the secondary piston forward
at the same time . When the pistons have moved forward,
hydraulic pressure is built up and transmitted through the
MASTER
CYLINDER
HYDRAULIC LINES
TO REAR-WHEEL
BRAKES
VACUUM BOOSTER
FRONT
Figure 6-1 -Typical Hydraulic System
SECTION 6-BRAKES
BRAKES
brake hydraulic lines to the front and rear brake assemblies
. Hydraulic pressure behind the wheel cylinder cups
forces the pistons outward, causing the brakes to be applied.
Braking action occurs as a result of friction between
the brake lining material and the metal surface of the rotor
disc or the drum.
As brake pedal force is reduced, brake fluid pressure in
the master cylinder is also reduced. This allows the drum
brake retractor springs to retract the shoe and lining assemblies
from contact with the drum which forces brake
fluid out of the wheel cylinder assemblies and back into
the master cylinder assembly. The reduction in fluid pressure
also allows the disc brake caliper pistons to retract
slightly by action of the piston seal . (See Figure 6-1 .)
BRAKE ROTOR
FRONT
BRAKE
CALIPER
DISC BRAKES
Upon application of the brakes, fluid pressure applied to
the piston(s) is transmitted to the inner shoe and lining,
forcing the lining against the inner rotor surface . The pressure
applied to the bottom of the piston bore(s) forces the
caliper to slide or move on the mounting bolts toward the
inner side, or toward the vehicle . Since the caliper is one
piece, this movement toward the vehicle causes the outer
section of the caliper to apply pressure against the back
NOTE: OVERSIZE SUPPORT
KEYS ARE AVAILABLE.
REFER TO GM
BULLETIN NO . 79-T-25
DATED JANUARY, 1980
(APPENDIX 6-1 AT THE
BACK OF THIS
SECTION)
OUTBOARD SHOE
AND LINING
Figure 6-2 - Disc Brake
SECTION 6
CALIPER
BOOT
PISTON
'~ INBOARD SHOE
OUTBOARD SHOE I CALIPER SPRING
ANTI-RATTLE SPRING
CALIPER INBOARD SHOE
AND LINING
6-2
BRAKES
of the outer shoe and lining assembly, forcing the lining
against the outer rotor surface . As line pressure builds
up, the shoe and lining assemblies are pressed against
the rotor surfaces with increased force, bringing the vehicle
to a stop. (See Figure 6-2.)
Lining wear is automatically compensated for by the outward
movement of the caliper and piston . Brake fluid fills
this void as lining wears.
SECTION 6 BRAKES
WHEEL CYLINDER LINKS
SECONDARY SHOE & LINING
SHOE GUIDE
PARKING BRAKE STRUT
STRUT SPRING
ADJUSTER LEVER
ACTUATING LINK -1 71
l0((
BRAKE SHOE
RETURN SPRINGS
0
OWNAAM
0
WHEEL
CYLINDER SCREWS
BACKING PLATE
HOLD DOWN I L ~-- HOLD DOWN SPRING
SPRING & CUP\ ADJUSTING SCREW SPRING
ADJUSTING SCREW
LEVER RETURN SPRINGS
J
HOLD _1
DOWN PINS
~ PARKING BRAKE LEVER
`- WHEEL CYLINDER
PRIMARY SHOE AND LINING
Figure 6-3-Typical Brake Drum Assembly
Figure 6-4- Power Brake Hydro-Boost
6-3
DRUM BRAKES
When the brake pedal is depressed, fluid is forced through
the brake lines into the piston . The wheel cylinder links
are then forced out against the brake shoes which exert
braking action on the drum . When the pedal is released,
the return springs pull the shoes away from the drum.
(See Figure 6-3 .)
POWER UNITS
Additional braking power is supplied through either a vacuum
booster or a Hydro-Boost. The master cylinder is
mounted on the forward end of the vacuum booster or
Hydro-Boost. (See Figure 6-4.)
The Hydro-Boost utilizes hydraulic pressure supplied from
the power steering pump. A spring accumulator is also
included in the booster to provide reserve braking power
in case pressure from the power steering pump is unavailable
. At normal curb idle with 150 lbs. of pedal pressure,
the Hydro-Boost could be expected to produce
1,600-1,850 lbs. of line pressure measured at any wheel
cylinder bleeder port. Similar pressures could be expected
of most vacuum boosters with good engine vacuum.
Figure 6-5- Parking Brake System
SECTION 6
Customers have expressed concern with their ability to
push the brake pedal to the floor with the vehicle stationary
and the engine running . If the Hydro-Boost brake pedal
is forced to the floor, as can be done, and the motion
stopping function and effectiveness of the brake system
is still considered normal, then the pedal travel action of
the Hydro-Boost brake system is also considered to be
normal . (See Pedal Travel Check in this section of the
manual.)
Figure 6-6
6-4
BRAKES
PARKING BRAKE(S)
Both the G-Series and P-Series are equipped with a parking
brake system. This system is mechanically operated
by a lever and strut or a pedal which will activate the rear
brakes only or the propshaft drum brake unit (P-Series
motor homes with a GVWR of 14,000 lbs. or more) . Very
little maintenance is required, but some periodic adjustment
is necessary . (See Figure 6-5.)
P-SERIES
WITH REAR WHEEL
PARKING BRAKES
WITH PROPSHAFT
PARKING BRAKE
CABLE TO
REAR WHEEL
BRAKES
NOTE: WITH REAR DRUM OR PROPSHAFT
DRUM PROPERLY ADJUSTED -
PROPER ADJUSTMENT OF THE
OPERATOR ORSCHELN PULL HANDLE
WILL REQUIRE 90 LBS. PULL OVER
FORCE.
See Figure 6-3 for typical brake drum assembly.
1 . Shoe Kit #1155270
' I/ 2. Drum &Flange #368008
SECTION 6
MAINTENANCE AND INSPECTION
FILLING THE MASTER CYLINDER
The master cylinder must be kept properly filled to ensure
adequate reserve and to prevent air from entering the
hydraulic system. However, because of expansion due to
heat absorbed from the brakes and from the engine, the
master cylinder must not be overfilled.
The -master cylinder is located under the floor on the
driver's side of the engine (P-Series), or on the cowl
(G-Series). The position of the master cylinder on the PSeries
may require the use of a flashlight and mirror to
check the fluid level .
Thoroughly clean the reservoir cover before removal to
avoid getting dirt into the reservoir . Remove the cover and
diaphragm. Add fluid as required to bring the level to
1/4 inch (plus or minus 1/8 inch) from the lowest portion
of the top of each reservoir . Use Delco Supreme No. II
Hydraulic Brake Fluid (DOT No. 3) or equivalent.
Do not use shock absorber fluid or any other fluid which
contains mineral oil . Do not use a container which has
been used for mineral oil or a container which is wet from
water. Mineral oil will cause swelling and distortion of rubber
parts in the hydraulic brake system and water will mix
with brake fluid, lowering the fluid boiling point. Keep all
fluid containers capped to prevent water contamination .
CAUTION : CHECK FOR LEAKS IF A LARGE AMOUNT
OF FLUID IS REQUIRED.
PEDAL TRAVEL CHECK
At periodic intervals, the motor home owner should inspect
the vehicle brake system for "pedal travel." Brake
pedal travel is the distance the brake pedal moves toward
the floor from the fully released position (foot not applied
to the brake). Brake pedal inspection should be made with
the brakes "cold ." With the engine turned off, depress the
brake pedal a minimum of four (4) times to exhaust all
vacuum and/or accumulator pressure . Applying approximately
90 pounds of pedal pressure, the distance the
brake pedal should travel is as follows :
G-Series with power brakes . . . . . . . . . . . . . . . . . . . . 3.5 inches
P-Series with drum rear brakes . . . . . . . . . . . . . . . . 3.5 inches
P-Series with disc rear brakes (JF9) . . . . . . . . . . 6.0 inches
BRAKE HOSE INSPECTION
The flexible hydraulic brake hose which transmits hydraulic
pressure from the steel brake pipe on the frame
to the rear axle and to the calipers should be inspected
regularly in accordance with the vehicle Maintenance
Schedule. The brake hose assembly should be checked
for road hazard damage, for cracks and chafing of the
outer cover, and for leaks and blisters . A light and mirror
may be needed for an adequate inspection. If any of the
above conditions are observed on the brake hose, it will
be necessary to replace it.
BRAKES
LINING INSPECTION
Inspect the brake linings per the vehicle Maintenance
Schedule and anytime the wheels are removed (tire rotation,
etc .) . Check both ends of the outer shoe by looking
at each end of the caliper . Check the lining thickness on
the inner shoe by looking down through the inspection
hole in the top of the caliper housing. Whenever the lining
is worn to the approximate thickness of the shoe, the shoe
and lining should be removed. After removal, measure the
lining thickness. The shoe and lining should be replaced
anytime the lining is worn to within 1/32 inch of a rivet or
of the shoe at any point, or when wear indicator contacts
the rotor. Always replace linings in sets (both right and
left front) .
Some front disc brakes have a wear indicator that makes
a noise when the linings wear to a degree where replacement
is required. (See Figure 6-6 .) The spring clip is an
integral part of the inboard shoe and lining . When the
lining is worn, the clip contacts the rotor and produces a
warning noise .,
Figure 6-7 - Disc Brake Wear Indicators
Check the flatness of the brake pads. Place inboard and
outboard pad surfaces together and check for a gap between
the pad surfaces . If more than a .005-inch gap is
measured at the middle of the pad (midway between attaching
lugs), the pad must not be used. This applies to
new or used brake pads. Whenever the front disc brakes
are relined, the rear brakes should also be checked .
BRAKE DRUM INSPECTION
Whenever brake drums are removed, they should be thoroughly
cleaned and inspected for cracks, scores, deep
grooves and out-of-round condition .
A cracked drum is unsafe for further service and must be
replaced . Do not attempt to weld a cracked drum.
Smooth up any slight scores. Heavy or extensive scoring
will cause excessive brake lining wear, and it will probably
be necessary to turn the drum on a lathe in order to true
up the braking surface.
If the brake linings are slightly worn and the drum is
grooved, the drum should be polished with fine emery
cloth but should not be turned . At this stage, eliminating
the groove in the drum would necessitate removal of too
much metal, while if left alone, the grooves and lining
ridges match and satisfactory service can be obtained .
If brake linings are to be replaced, a grooved drum should
be turned for use with new linings. A grooved drum, if
used with new lining, will not only wear the lining, but will
make it difficult, if not impossible, to obtain efficient brake
performance .
An out-of-round drum makes accurate brake shoe adjustment
impossible and is likely to cause excessive wear
of other parts of brake mechanism due to its eccentric
action . An out-of-round drum can also cause severe and
irregular tire tread wear as well as a pulsating brake pedal.
When the braking surface of a brake drum exceeds the
factory specification limits in taper and/or being out of
round, the drum should be turned to true up the braking
surface .
BRAKE ROTOR INSPECTION
To prevent brake roughness, the rubbing surfaces of the
rotor must be flat, parallel and with lateral runout held to
a minimum. The surface finish should be smooth to avoid
pulling or erratic brake performance . Light scoring which
results from normal use is not detrimental to brake operation
if the scoring does not exceed .015 inch in depth.
Lateral runout, the side-to-side movement of the rotor as
it rotates, if'excessive (over .004 inch total indicator reading),
can cause vibration when the brakes are applied . It
is checked using a dial indicator gage which a qualified
service shop should have.
DISC BRAKE SQUEAL OR SQUEAK
SECTION 6-BRAKES
A persistent amount of "squeal or squeak" is often associated
with heavy-duty disc brake usage. These noises
are common for both foreign and domestic disc brake
systems . Heat, humidity and severity of usage seem to
be contributing factors to brake noise. Changing the brake
pads, or rotor refinishing as a repair, is often considered
a temporary repair, or even, by some technicians as useless.
The recommended aproach is to have an inspection
to assure there is free and proper operation of all caliper,
parts. At this point, the owner should realize that the brake
noise exists, but is not detrimental to overall brake life.
BRAKE CALIPER NOISE
Sometimes on vehicles with high mileage, a noise or rattle
condition caused by wear at the brake caliper and knuckle
slide surfaces may be encountered. This condition does
not affect the operation of the brake system, but the noise
or rattle condition can be corrected by installing an oversized
key and spring available as a service replacement.
GM Bulletin 79-T-25 (Jan . 1980) in Appendix 6-1 at the
back of this section provides details for selecting the
proper size replacement key and how to install the key.
BRAKE PEDAL/STOPLIGHT ADJUSTMENT
NOTE: The adjustments listed below do not change with
time or miles. An incorrect adjustment would normally
be noted in the first few miles of vehicle life
or after service work of some kind performed under
the dash resulting in system malfunction .
1 . Check for a full upward and full release of the brake
pedal. Determine if the stoplight switch, cruise control
switch or any other item does not allow full upward
pedal travel. (See Figure 6-7.) The stoplight switch/
brake pedal mounting bracket provides automatic adjustment
when the brake pedal is manually returned
to its mechanical "up-stop" position .
2. Pull the brake pedal fully rearward against the pedal
stop until audible "click" sounds can no longer be
heard . This moves the stoplight switch assembly in a
tubular clip, as shown in Figure 6-7, and provides a
proper adjustment.
NOTE : Proper adjustment of the stoplight switch allows
.06 inch to .36 inch free pedal travel and will turn
on the stoplight switch after approximately .40
inch travel. (See Figure 6-8 .)
BRAKE PEDAL
MOUNTING BRACKET
CRUISE CONTROL
ONLY
(WITH CRUISE CONTROL)
(WITHOUT CRUISE
CONTROL)
NOTE: Refer to bulletin section on pads that will help
reduce brake noise on pre 1992 units. Figure 6-8 - Brake Pedal/Stoplight Switch Assembly
6-6
3. Check the 31-inch rod that runs down the front of the
chassis and connects the brake pedal to the Hydro-
Boost for proper adjustment. (See Figure 6-8 .) The rod
can be adjusted (longer or shorter) using the screw
adjustment located at the bottom of the rod . Block the
wheels and hold the inside pedal in the "full-up" position
. Check that there is free entry of the special bolt
through the relax4d pedal rod lever connecting the
linkage into the Hydro-Boost. Turn the adjustment
screw to lengthen or shorten the rod as necessary.
4. Tighten the adjusting lock nut to 22-30 ft. lbs. then
tighten the nut on the special bolt and install a new
cotter pin .
NOTE : Newer model rods can not be adjusted.
SECTION 6
PEDAL BUMPER
.06" TO .36" FREE
PEDAL TRAVEL
.40" PEDAL TRAVEL
REQUIRED TO TURN
STOPLAMP SWITCH ON
PEDAL ROD LEVER
PEDAL ROD END
Figure 6-9 - Actuating Rod/Brake Pedal/Stoplight
Adjustment
BLEEDING BRAKE HYDRAULIC SYSTEM
A bleeding operation is necessary to remove air whenever
it is introduced into the hydraulic brake system .
It may be necessary to bleed the hydraulic system at all
four wheel cylinders if air has been introduced through
low fluid level or by disconnecting the brake pipes at the
master cylinder. If a brake pipe is disconnected at any
wheel cylinder, then that wheel cylinder only needs to be
bled. If pipes are disconnected at any fitting located between
the master cylinder and wheel cylinders, then all
wheel cylinders served by the disconnected pipe must be
bled.
BRAKES
NOTE : The following procedure is for manual bleeding
of the brakes only. If possible, obtain approved
commercial pressure-bleeding equipment or the
GM Tools Vacuum Brake Bleeder. (See the GM
Wheel Service System Brake Bleeder in Appendix
6-2 at the back of this section for further information
regarding Brake Bleeder specifications,
usage and ordering information .)
With power brakes, remove the vacuum reserve by applying
the brakes several times with the engine off . Then,
complete the following steps:
1 . Fill the master cylinder reservoirs with brake fluid and
keep at least one-half full of fluid during the bleeding
operation. (See Figure 6-1 .)
2. If the master cylinder is known or suspected to have
air in the bore, then it must be bled (before bleeding
any wheel cylinder or caliper) in the following manner:
a. Disconnect the forward (blind end) brake pipe connection
at the master cylinder.
b. Allow brake fluid to fill the master cylinder bore until
it begins to flow from the forward pipe connector
port.
c. Connect the forward brake pipe to the master cylinder
and tighten .
d. Depress the brake pedal slowly one time and hold.
Loosen the forward brake pipe connection at the
master cylinder to purge air from the bore. Tighten
the connection and then release the brake pedal
slowly. Wait 15 seconds. Repeat the sequence, including
the 15-second wait, until all air is removed
from the bore. Care must be taken to prevent brake
fluid from contacting any painted surface.
e. After all air has been removed at the forward connection,,
bleed the master cylinder at the rear (cowl)
connection in the same manner as the front, as in
Step "d" above.
f. If it is known that the calipers and wheel cylinders
do not contain any air, then it will not be necessary
to bleed them.
3. Individual wheel cylinders or calipers are bled only after
all air is removed from the master cylinder.
a. Place a proper size box-end wrench over the
bleeder valve. Attach transparent tube over valve
and allow tube to be hand submerged in brake fluid
in a transparent container . Depress the brake pedal
slowly one time and hold. Loosen the bleeder valve
to purge the air from the cylinder. Tighten bleeder
screw and slowly release pedal. Wait 15 seconds .
Repeat the sequence, including the 15-second wait
until all air is removed. It may be necessary to repeat
the sequence ten or more times to remove all
the air.
4 . If it is necessary to bleed all of the wheel cylinders and
calipers, the following sequence should be followed :
1) Right-rear wheel cylinder; 2) Left-rear wheel cylinder;
3) Right-front caliper ; 4) Left-front caliper .
5. Check the brake pedal for "sponginess" and the brake
warning light for indication of unbalanced pressure .
Repeat entire bleeding procedure to correct either of
these two conditions.
BLEEDING HYDRO-BOOST BRAKE SYSTEM
Whenever the booster is removed and reinstalled, the
steering system should be bled as outlined below.
NOTE: Power steering fluid and brake fluid cannot be
mixed. If brake seals contact steering fluid or
steering seals contact brake fluid, seal damage
will result.
1 . Fill fluid reservoir to the proper level and let the fluid
remain undisturbed for at least two minutes.
2. Start the engine and let it run momentarily.
3. Add fluid if necessary.
4. Repeat above procedure until the fluid level remains
constant after running engine.
8. Lower the vehicle .
SECTION 6
5. Raise front end of the vehicle so that the wheels are
off the ground .
6. Turn the wheels (off ground) right and left, lightly contacting
the wheel stops.
7. Add fluid if necessary.
9. Start engine and depress the brake pedal several
times while rotating the steering wheel from stop to
stop .
10. Turn engine off and. then pump the brake pedal 4-5
times to deplete accumulator pressure.
11 . Check the fluid level and refill as required .
12. If fluid is extremely foamy, allow vehicle to stand for
a few minutes with the engine off and repeat above
procedure .
a. Check belt tightness and check for a bent pully.
(Pulley should not wobble with engine running .)
b. Check to make sure hoses are not touching any
other parts of the vehicle, particularly the sheet
metal.
6-8
BRAKES
c. Check the reservoir fluid level, filling it to the proper
level if necessary, following operations 1 through
10. This step and step "d" are extremely important
as low fluid level and/or air in the fluid are the most
frequent causes of objectionable pump noises.
d. Check for the presence of air in the fluid. Air will
show up as a milky-looking fluid. If air is present,
attempt to bleed the system as described in operations
1 through 10. If it becomes obvious that
the pump will not bleed after a few trials, refer to
the appropriate shop manual for more detailed test
procedures.
13. The presence of trapped air in the system will cause
the fluid level in the pump to rise when the engine is
turned off. Continue to bleed the system until this
condition no longer occurs.
POWER BRAKE UNITS
The hydraulic lines connecting the power steering pump,
Hydro-Boost unit and steering gear, as well as the components
themselves, should be checked regularly for
signs of leaks, damage or deterioration on vehicles so
equipped . For vehicles with vacuum boosters, inspect the
vacuum hoses and booster chamber for damage or
deterioration .
NOTE: Power steering fluid and brake fluid cannot be
mixed . If brake seals contact steering fluid or
steering seals contact brake fluid, seal damage
will result.
Both the vacuum booster and Hydro-Boost should be
serviced by a qualified repairman .
PARKING BRAKE
Adjustment of the parking brake cable is necessary whenever
holding ability is not adequate or whenever the center
brake cables have been disconnected . An improperly adjusted
parking brake cable may also cause the brakes to
drag. On 16,000# GVW units, the transmission must be in
neutral .
The service brakes must be properly adjusted as a base
for parking brake adjustment ; conversely, the parking
brake must be properly adjusted for the service brake to
function as intended .
Inspection
If a complete release of the parking brake is not obtained,
unless it is forcibly returned to its released position, or if
application effort is high, check parking brake assembly
for free operation. If operation is sticky or a bind is experienced,
correct as follows :
1 . Clean and lubricate brake cables and equalizer with
Delco Brake Lube (or equivalent) .
2. Inspect brake assembly for straightness and alignment
(replace if necessary).
3. Clean and lubricate parking brake assembly with Delco
Brake Lube (or equivalent) .
4. Check routing of cables for kinks or binding .
Drum Balance
An imbalanced parking brake drum can cause vibrations .
If a vibration occurs, perform the following to check for an
imbalance problem with the parking brake drum :
1 . Place the transmission into NEUTRAL and increase
the engine speed to the approximate speed that the
vibration is felt while driving the vehicle on the road .
2. If the vibration has disappeared, check the parking
brake drum on the back of the transmission if so
equipped.
3. Disconnect the propeller shaft at the back of the transmission
and remove the drum .
4. Retest as in Step 1; If the vibration is gone, replace
the drum. (See Figure 6-9 .)
NOTE: If a strobe light wheel balancer is available, position
the strobe pick-up against the transmission
pan. Adapt the procedure listed in the Driveline
Balance section of this manual to check for a
balanced drum. Add weight under the retaining
bolt of the parking brake drum as necessary .
Cable Adjustment
FOOT PEDAL TYPE (G-P series) - Before adjusting
parking brake, check service brake condition and
adjustment.
1 . Loosen the equalizer adjusting nut .
2. Apply parking brake four notches from fully released
position. Only 1 notch on P series .
3. Tighten the equalizer nut until a moderate drag is felt
when the rear wheels are rotated forward. (See NOTE
at the end of this procedure .)
4. Fully release parking brake and rotate the rear wheels.
No drag should be present.
ORSCHELN LEVER TYPE (P-SERIES) -
1 . Turn adjusting knob on parking brake lever counterclockwise
to stop.
2. Apply parking
SECTION 6-BRAKES
6-9
3. Loosen nut at intermediate cable equalizer and then
adjust nut to give light drag at rear wheels. (See NOTE
at the end of this procedure .)
4. Readjust parking brake lever knob to give a definite
snap-over-center feel . Proper pull-over force is 90
pounds.
NOTE: This fastener is an important attaching part in that
it could affect the performance of vital components
and systems, and/or could result in major
repair expense. It must be replaced with one having
the same part number or with an equivalent
part if replacement becomes necessary. Do not
use a replacement part of lesser quality or substitute
design ;
Propeller Shaft Drum-Type Brake
Adjustment (Adjustment - Drum On)
Refer to Figure 6-9 .
1 . Using a jack, raise vehicle so that at least one rear
wheel is off ground . Block wheels and release the hand
brake.
2. Remove cotter pin and clevis pin connecting the pull
rod and relay lever. This will assure freedom for full
shoe release .
NOTE : It may be necessary to knock out lanced area in
brake drum (or backing plate) with punch and
hammer to gain entry to adjusting screw through
brake drum . Be sure to remove any metal that
has fallen inside the parking brake drum.
3. Rotate brake drum to bring one of the access holes
into line with adjusting screw at bottom of shoes (manual
transmission), or top of shoes (automatic
transmission) .
4. Expand shoes by rotating adjusting screws with a
screwdriver inserted through hole in the drum . Move
outer end of screwdriver away from the drive shaft.
Continue adjustment until shoes are tight against drum
and drum cannot be rotated by hand. Back off adjustment
and check drum for free rotation .
5. Place parking brake lever in the fully released position .
Take up slack in the brake linkage by pulling back on
cable just enough to overcome spring tension . Adjust
clevis of the pull rod or front cable to line up with hole
in the relay levers .
a. Insert clevis pin and cotter pin,-then tighten clevis
locknut .
b. Install anew metal hole cover in drum to prevent
contamination of the brake.
c. Lower rear wheels. Remove jack and wheel blocks.
See Note under Cable Adjustment procedure in this
section .
The parking brake system on the 199016,000 pound GVW
P3 motorhome chassis incorporates a unique automatic
apply feature with an internal expanding parking brake. The
system is different than the 1989 and 1991 systems of the
same model . The parking brake is spring applied and
hydraulically released. Hydraulic pressure is supplied by
the power steering pump. Full brake disengagement requires
that 95-115 PSI pressure existat the brake actuator .
The parking brake can be applied by using a hand button
or automatically when the shift lever is in the park position .
The system features an HR-1 relay valve serving as a flow
control point. The HR-1 reduces and directs flow to and
from a spring actuator operating the parking brake (See
Figure 6-10).
Hydraulic System (Fig . 6-10)
Steering fluid under pressure is supplied from the power
steering pump which is then routed through the brake
Figure 6-1 0
SECTION 6 BRAKES
AUTOMATIC APPLY PARKING BRAKE
1990 P3 MOTOR HOME (16,000# GVW ONLY)
hydro-boost unit on to the power steering gear to port #1 of
the HR-1 relay valve thus pressurizing the system. All fluid
is then directed back to the power steering pump by way of
port #2 on the relay valve. Pressurized fluid is then directed
to port #3 of the HR-1 relay valve where it is held at port "A"
of the manual apply control valve . Fluid (assuming the shift
selector lever is not in the "park" position) is directed out of
port "B" of the manual valve to port °D" of the shift actuated
control valve. Ports "C" on the manual valve and "F" on the
shift valve are used to exhaust fluid and direct it back to the
power steering pump reservoir and are always at zero
pressure. Port "E" on the shift control valve is used as a
"signal" pressure (fed to port #4 of the relay valve) to shuttle
the relay valve to either channel pressurized fluid to or
exhaust it out of the hydraulic brake actuator (port #5 of the
relay valve) thereby releasing or applying the park brake
assembly.
Various modes of operation are as
follows:
Vehicle in park, engine running, manual
apply control valve in the "released" position
(Fig. 6-11)
Pressurized fluid is directed from port #3 of the relay valve
to port "A" of the manual valve, on through the manual valve
to its port "B" and then on to port "D" is blocked and
prevented from entering the valve. Also, ports "E" and "F"
are now hydraulically connected. With this connection, any
SECTION 6-BRAKES
fluid that was previously pressurized at port #4 of the relay
valve, is allowedto pass through the shift valve and exhaust
back to the power steering pump reservoir . With the lack of
pressurized fluid at port #4 on the relay valve, pressurized
fluid from port #1 of the relay valve is blocked inside of the
valve preventing it from reaching port #5 and charging the
brake actuator . Ports #5 and #6 of the relay valve are now
internally connected. This allows the fluid in the brake
actuator to exhaust through the relay valve and on to the
power steering pump reservoir. With no hydraulic pressure
at the actuator, spring pressure is free to apply the park
brake.
Figure 6-1 1
SECTION 6
.Vehicle in any gear position other than "park",
engine running, manual apply control valve
in the "released" position (Fig. 6-12)
Ports "E" and "F" of the shift valve are not hydraulically
connected . Port "E" is connected with port "D" directing a
signal feed to port #4 of the relay valve. This signal feed
BRAKES
actuates the relay valve which blocks the connection of
ports #5 and #6 in the relay valve and prohibits the exhausting
of the brake actuator. Ports #1 and #5 of the relay valve
are internally connected allowing pressurized fluid to be
directed to the brake actuator which forces the actuator
spring to be compressed and the park brake to release .
Figure 6-1 2
SECTION 6
Vehicle in apy gear position other than "park",
engine running, manual apply control valve
in the "applied" position (Fig. 6-13)
Ports "A" and "B" of the manual valve are not connected .
Pressurized fluid at port "A" is blocked, preventing it from
entering the valve . Ports °B" and "C" are hydraulically
connected. This allows any fluid that was previously directed
to port ""D'" of the shift valve to exhaust back to the
power steering pump reservoir . With no pressurized fluid
available at port "ID" of the shift valve, no signal feed can be
supplied to port #4 of the relay valve (via the internal
connection between ports "D" and "E" of the shift valve
based on the position ofthe shift valve) . This lack ofa signal
feed allows the relay valve to actuate, blocking the flow of
Figure 6-1 3
BRAKES
pressurized fluid from port #1 to port #5 in the valve and
opening the passage between ports #5 and #6 allowing the
fluid from the actuator to exhaust. With no pressurized fluid
to release the actuator, spring pressure takes over and
applies the park brake.
Operational Features
1 . In the event the vehicle stalls, the wheels can be spun
freely for at least ten minutes until pressure is drained
from the brake actuator and the spring brake reapplies .
2 . A parking brake light in the vehicle warns the operator
when the brake is applied . This brake light will come on
when the pressure at the actuator is less than 60 PSI .
SECTION 6
The parking brake system on the 1991 and 1993 16,000
pound GVW P3 motorhome chassis incorporates a revised
system from the 1990 . The Park position brake is spring
applied and hydraulic released, the same as 1990. The
1991-93 system incorporates a manual Parking brake
pedal which applies the system when the shift indicator is
in any position other than Park.
With the shift selector in park; Engine running; and the
manual foot lever in the released position, fluid will
flow from the steering gear to port "SR" on the relay
valve, through the relay valve and out port "TW" to the
control valve supply port "SC" . Once the system is
charged, the pressure should range between 130 and
150 psi . Any excess fluid will be discharged through
port "R" back to the pump. The supply port or charge
port "SC" is blocked off due to the control valve position
in the park mode.
Any previously built pressure in the control valve flows
through the control valve out port "EC" back through
70
70 . Bolt
71 . Actuator Air Bleed
72. Actuator
73. Inlet Pipe Seal
74 . Connector
75 . Actuator Inlet Pipe
76 . Actuator Bracket
1 . Parking Brake Cable
6-1 1
BRAKES
AUTOMATIC APPLY PARKING BRAKE
1991-1993 P3 MOTOR HOME (16,000# GVW ONLY)
the relay valve, this triggers a release of pressure from
port "D" of the relay, valve through port "ER" to the
reservoir . This allows the spring controlled actuator to
apply the parking brake. The spring will apply the
brake by traveling as far as the brake adjustment demand
requires to balance brake apply and spring
force.
When the valve is released from the park position, the
fluid charge at the shift control valve port "SC" is
diverted to port "DC". The shift control port "EC" is
blocked off. The fluid charge at the relay valve port
"SR" is diverted to port "D", this pressurizes the parking
brake system and actuator. The fluid pressure
working against the spring pressure in the actuator
releases the parking brake.
The manual foot lever should still be applied whenever
the vehicle is shifted into park. This will alert the driver
of the need for adjustment in the parking brake
system.
78 77
66. Parking Brake Control Rod
67. Steering Column
77. Transmission Control Equalizer
78. Jam Nut
79. Control Valve Lever
1 .
2.
3.
4.
5.
6.
7.
8.
9.
10 .
Power Steering Pump
Reservoir
Parking Brake Pedal
Actuator
Parking Brake
Pressure Switch
Control Valve
Relay Valve
Steering Gear
Master Cylinder
10
SR - Supply to Relay Valve
TW -Supply to Control Valve
R -Return to Pump
TWE -Control Valve Exhaust
ER -Exhaust to Reservoir
D -Delivery to Actuator
C -Control Signal
DC -Delivery From Control Valve
SC -Supply to Control Valve
EC -Exhaust From Control Valve
SECTION 6
28 29 Removinglinstalling Parking Brake Pedal
on P Motorhome Models
28. Bracket
29. Bon
30. Parking Brake Pedal
31 . Brace
32. Nut
31
6-1 2
BRAKES
43 . Actuator Cable P-Motorhome Model
44 . Clevis Pin
45 . Clevis Pin Relay Lever Assembly
46. Washers (3)
47. Washers (2)
48. Cotter Pin
49. Cotter Pin 52
50. Front Parking Brake Cable
51 . Clevis Pin
52. Cotter Pin
56 . Bracket
50
43
Relay and Control Valve
64 . Bolt
65. Control Valve
66. Parking Brake Control Rod
67. Steering Column
68. Relay Valve
69. Nut
P-Motorhome Model Cable Components
50 . Front Parking Brake Cable
43. Actuator Cable
53 . Brake Drum
54. Actuator Bracket
55 . Bolt and Clip
56. Bracket
BRAKE CALIPER NOISE
Reference: General Motors Dealer Service Technical
Bulletin No. 79-T-25 (January, 1980)
1974-1979 G-, P-30 Series Models with JB-8 or JF-9
Brake Option
The following information has been extracted from the
above mentioned bulletin .
A noise or rattle condition caused by wear at the brake
caliper and knuckle slide surface may be reported on
some high-mileage vehicles as a loose or rattling front
end on all but smooth roads. This condition does not affect
the operation of the brake system. The J13-8 and JF-9
brake systems have a caliper retention design which incorporates
a key and a leaf spring retained in a "V"
groove .
Vehicles which have the caliper rattle condition can be
corrected by installing an oversized key and newly designed
leaf spring available from General Motors Parts
Division. The service keys will be available in five sizes
(at .040-inch increments) to compensate for varying degrees
of wear.
Follow the procedure given below for correction of complaint
vehicles:
1 . Remove caliper from knuckle by unscrewing key retention
screw and tapping out key and spring.
2. Clean surfaces "A", "B", "C", and "D" (shown in the
following illustration) with a wire brush, filing smooth
any nicks and/or gouges.
APPENDIX 6-1
3. Lay a straight edge across the forward caliper surfaces
"C" and "D" (shown in the following illustration) and
measure with a feeler gage the,maximum depth of any
wear on these surfaces. Calipers worn to a depth of
.050 inch or more should be replaced .
4.
5.
6.
8.
6-13
Reinstall the caliper back into the knuckle. Install a
new standard size key .and reinstall the key retention
screw, but do not install the caliper support spring at
this time.
Insert a screw driver into center of key/bumper gap
and pry firmly to assure that caliper is seated against
three slide surfaces -,"A", "B", "C .''
Measure bumper gap with largest feeler gage (or stack
of gages) that will fit into the gap for its full length .
7. Select a replacement key according to the table on
page 6-12.
Install selected replacement key and new design
spring, GM Part No. 14023437, and reinstall retention
screw.
NOTE:
" If retention screw is damaged or shows signs of excessive
wear, replace with new part (GM Part No . 331478) .
" The spring has been redesigned from a "C" to an "M"
shape. The "M" spring must be installed with the large
radius in contact with the key.
APPENDIX 6-1
BRAKE CALIPER NOISE (Cont'd)
°C" SHAPE SPRING (OLD DESIGN)
"M" SHAPE
SPRING (NEW DESIGN)
BUMPER GAP (IN .)
MORE THAN BUT NOT" EXCEEDING REPLACEMENT KEY I.D. GM PART NO.
0 .060 Standard Size 1 14023439
.060 .100 .040 Oversized 11 14026793
.100 .140 .080 Oversized 111 14026794
.140 .180 .120 Oversized 1111 14026795
.180 .220 .160 Oversized 11111 14026796
.220 -
Replace Anchor Plate/Knuckle and
Caliper and use new standard size key
and new spring .
VACUUM BRAKE BLEEDER
The following information has been extracted from the GM
Dealer Equipment Catalog. Vacuum brake bleeder features,
specifications and ordering information has been
described .
FEATURES
" Vacuum operation
" Can be used for all types of cars, trucks, busses and
motor bikes.
" Fluid is retained in the canister, eliminating costly paint
damage from splashing .
" Brake set equipped with universal rubber connector on
40-inch quick-connect tubing and GM adapter.
SPECIFICATIONS
Air Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 CFM
Minimum vacuum capacity . . . . . . . . . . . . . . . . . . . . . . . . . .60%
Connection thread . . . . . . . . . . . . . . 1/4-inch female thread
Canister volume. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 gal .
HOW IT WORKS
The brake bleeder is used as outlined below:
1 . Connect the brake bleeder to an air supply (80 to 175
PSI) and the hose with the rubber connector end to
the brake bleed screw.
2. Depress the lever on the bleeder top to create a vacuum
in the canister.
3. Apply a suitable wrench to the bleed screw, and open .
Air and brake fluid will now be drawn out of the system.
APPENDIX 6-2
VEHICLE #1 VEHICLE #2
BRAKES APPLIED AT "Y" BRAKES APPLIED AT "X"
BRAKE LINING LIFE
EXPECTANCY
~10P
VEHICLE 2
B.1U.'s fill B.TU.'s MMUJ
TOTAL HEAT GENERATED IN BRAKES IS THE SAME FOR BOTH VEHICLES
150 HP ABSORBED
I--x.900 HP ABSORBED-y
VEHICLE #1 AND VEHICLE #2 TRAVELING AT SAME SPEED WHEN
The following information is provided courtesy of Gray-
Rock Company as an aid to the motor home owner in
understanding brake lining life expectancy and premature
drum failure. GM provides no statement as to the accuracy
of this information, although it would appear to be correct .
A brake is a heat machine. A soft touch on the brakes
pays off in any model vehicle in the form of brake life and
fuel economy. Each time brakes are applied, you are converting
forward motion (that you bought and paid for as
fuel costs) into heat energy of stopping .
Brakes change energy of motion to heat energy, and this
energy is the same for any stop from a given speed. Many
drivers take advantage of good brakes by stopping in
shorter distances than necessary. The following example
demonstrates improper braking techniques and the results
. (See diagram above.)
Assume both drivers (Vehicle No. 1 and No. 2) are operating
identical vehicles and making a stop from the same
speed. Vehicle No. 1 anticipates the stop and applies the
brakes at point "Y" as shown in the diagram above . Heat
is generated at a rate that the brakes of Vehicle No. 1
can handle - about 500°F at drum surface . The driver of
Vehicle No. 2, shown in the diagram, doesn't apply his
brakes until he reaches point "X."
Although the work load on the brakes of both vehicles is
the same, in the case of Vehicle No. 2, the work load is
"poured" into the brakes in 1/6th the time. This means
that the brakes must absorb 900 horsepower instead of
just 150. Vehicle No. 2 develops up to 2,000°F temperature
at drum surface and at a rate faster than it can be
transferred and dissipated. The result is short lining life
and premature drum failure.
APPENDIX 6-3
BRAKES ARE APPLIED
6-16
BRAKE DRUMS ON VEHICLE #1
DURING BRAKE APPLICATION
MINIMUM INPUT
FOR SAFE STOP
500°F - NORMAL HEAT
CONCENTRATION AT DRUM SURFACE
BRAKE DRUMS ON VEHICLE #2
DURING BRAKE APPLICATION
MAXIMUM INPUT
"K FACTOR" WILL ALLOW
1800-2000°F - HIGH HEAT
CONCENTRATION AT DRUM SURFACE
Your Chevrolet Motor Home Chassis is equipped with
either the 5.7L or 7.4L (Mark IV) gasoline engine or the
6.2L diesel engine. Both the gasoline and diesel engines
are four-cycle designs. That is, there are four distinct
strokes (intake, compression, power and exhaust) in the
power cycle of each. engine cylinder. The power cycle of
a cylinder takes plce through two .revolutions of the
crankshaft.
NOTE: There is a "truck rule of thumb" that says, "For
good engine life, the engine shall not cruise for
long periods of time at speeds in excess of 80
90 percent of engine governed speed or as
rated ." Full-rated speed is acceptable for short
durations such as when the transmission is going
through its shift points . The chart shown in Figure
7-1 shows the general relationship of engine
speed to engine life.
PRINCIPLES OF INCREASED ENGINE LIFE
Avoid Engine Idling For Long Periods Of
Time
Long periods of engine idling will drop engine temperature
and result in the incomplete burning of fuel. Raw unburned
fuel can wash lubricating oil off cylinder walls and result
in diluted crankcase oils and poor lubrication to all moving
parts.
High Operating Temperatures Increase Oil
Oxidation Rate
High engine temperatures that are caused by heavy loads,
faulty cooling systems, incorrect timing, improper spark
plugs, preignition and detonation, help to speed the oxidation
of oils . Every 20 degree increase of temperature
will double the oxidation rate. (See Figure 7-10.)
Extreme heat causes the'oil to oxidize which forms tar
and gum deposits inothe oil . Varnish will also form and
result in ring sticking, valve sticking and malfunction of
other vital engine parts .
Clean oil coolers have proven successful in maintaining
acceptable engine temperatures .
Allow Engine To "Cool Down" Slightly
Before Shut-Down
If an engine has been heavily worked, it is a good policy
to disengage the load from the engine and allow the engine
to idle for a few minutes before turning off the ignition .
This practice allows the engine to cool gradually and promotes
a desirable dissipation of heat from any localized
area of concentrated temperature. Such a practice avoids
the rapid cooling that can cause warped valves, valve
"tuliping," block distortion, cracked manifolds, etc. (See
the Exhaust Manifold and Plug Wire Failure section for
additional information, page 7-4 .)
SECTION 7 -- ENGINE
ENGINE
Figure 7-1- Engine Speed to Engine Life
Water Temperature Is Important To Engine
Operation And Engine Life
Water temperature of 195 degrees Fahrenheit or higher
assures that cylinder walls are heated to a proper temperature
needed to support good combustion and that
other working parts of the engine have expanded evenly
to favorable clearances for oil lubrication.
When water temperature , is too low, the cylinder
walls retard the heating of air during compression and
delay ignition . This causes incomplete combustion, excessive
exhaust smoke, poor emissions, and high fuel
consumption .
Water Condensation In A Cold Engine
Creates Unnecessary Engine Wear
It has been well established that low operating temperature
increases engine wear. The products of combustion
in a "cold-running" engine combined with moisture will
form a corrosive film of oxide on the cylinder walls and
engine components.
Engineers have estimated that as much as eight times
the cylinder and engine wear occurs to an engine operating
at temperatures to 100 degrees Fahrenheit compared
to an engine operating at a temperature of 195
degrees Fahrenheit.
Avoid Initial "Scuffing" After Engine
Rebuild
After an engine has been overhauled, a pressurized oil
system helps prevent damage to newly installed engine
parts caused from a lack of lubrication. The system sends
a supply of oil through the oil lines to the lifters, bearings,
etc ., before the engine starts .
Design engineers have approximated that'several
hundred engine revolutions are required before the average
lubrication system will supply the required amount
of oil to the vital moving parts. This time lapse results
because a normal oil pump must prime itself and then
pump the oil throughout the system.
If a newly overhauled engine is "dry" when started, the
newly installed parts will be more sensitive to break-in
abuse due to the high frictional temperatures caused by
the momentary lack of oil .
GASOLINE ENGINE
SECTION 7
Both the 5.71-(350 Cubic Inch Displacement) and the 7.41-
Mark IV (454 Cubic Inch Displacement) engines have
eight cylinders and are designed to operate on no-lead
gasoline .
1982-1989
Basic Specifications
Engine type . . . .
. . . . . .
. . . . . .
. .
. . . . . . . Valve-in-head
Piston displacement (Liter/Cu . In .) . . . . . . . . . . . . 7 .41454
Bore & stroke (nominal) . . . . . . . . . . . . . . . . 4 .25" x 4.00"
Compression ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 .9 :1
Carburetor type . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Barrel
Exhaust - Single . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . All
Engine Ratings - Typical
All States
Heavy Duty Emissions
(8501 lbs. GVWR and above)
SAE net horsepower (77 °F) . . . . . . . . . . . 240 @ 3800 rpm
SAE net torque ft-lb (77°F) . . . . . . . . . . . 375 @ 3200 rpm
0 4 8 12 16 20 24 28 32 36 40 44 48
REVOLUTIONS PER MINUTE (+100)
Figure 7-2 - Typical 7.4L Engine Ratings and
Specifications
7-2
ENGINE
Each is equipped with an electronic ignition system which
has no breaker points or condenser. The system uses a
spark plug in each cylinder to start combustion.
Typical 7.41- engine ratings and basic specifications are
shown in Figure 7-2 and 7-3.
DIESEL ENGINE
The V-8, 6.21- diesel engine is similar to a V-8 gasoline
engine in many ways but major differences exist in the
cylinder heads, combustion chamber, fuel distribution system,
air intake manifold and the method of ignition . The
cylinder block, crankshaft, main bearings, rods, pistons
and wrist pins are similar to those on a gasoline engine
but are of a heavy-duty design because of the high
compression ratio required in the diesel engine to ignite
fuel. Ignition of the fuel in a diesel engine occurs because
of heat developed in the combustion chamber during the
compression stroke . Thus, no spark plugs or high-voltage
ignition are necessary for a diesel engine.
Typical 6.21- engine ratings and basic specifications are
shown in Figure 7-4.
Basic Specifications
Engine type . . . . . . . . . . . . : . . . . . . . . . . . . Valve-in-head
Piston displacement (Liter/Cu . In .) . . . . . . . . . . . . 7.4/454
Bore & stroke (nominal) . . . . . . . . . . . . . . . . 4 .25" x 4 .00"
Compression ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 .9 :1
Carburetor type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TBI
Exhaust - Single . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . All
Engine Ratings - Typical
All States
Heavy Duty Emissions
(8501 lbs . GVWR and above)
SAE net horsepower (77 °F) . . . . . . . . . . . 230 (?a 3600 rpm
SAE net torque ft-Ib (77 °F) . . . . . . . . . . . 385 Q 1600 rpm
1990-1994
I I I I 1 I I I I I
4 8 12 16 20 24 28 32 38 40 44 48
ENGII4E RPM (+100)
-500
m
KF
Figure 7-3 - Typical 7.41- Engine Ratings and
Specifications
250 ..... .. .............s... s40 230
240 520 220
230 I::: 500 210
220 460
200
210 : :cast 460
190
200 440
180
180 420
180 400 170
:a33
170 380 180
z
160 .H.: 360 0 ~3' ISO
0
150 340 140
140 320
N
C 130
130 300 S
120
120 280 110
110 260
100
100 240
80
80 220
:::.': s0
..3- . ..-.--~ ....3 .3 .339*. 200
70 160 70
60 ::ISilt 160 60
50 I I I I I I I I I I I 1 140 $0 1
0
SECTION 7D
Engine type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Four cycle
No. of cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Bore & stroke . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.06" x 3 .82"
Displacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 cu . in .
Injection pump . . . . . . . . . . . . . . . Stanadyne Mechanical Type
Brake HP . . . . . . . . . . . . . . . . . . . . . . 155 BHP @ 3500 RPM"
Peak Torque . . . . . . . . . . . . . . . . . . . 285 lb . ft . @ 2000 RPM'
Comp. Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 .3 :1
Engine Specifications
Figure 7-4- Typical 6.21- Engine Ratings and
Specifications
ENGINE FUEL SYSTEMS
Engine Specifications
Engine type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Four cycle
No. of cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Bore & stroke . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 .98" x 3 .82"
Displacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 cu . i n .
Injection pump . . . . . . . . . . . . . . . Stanadyne Mechanical Type
Brake HP . . . . . . . . . . . . . . . . . . . . . . 190 BHP @ 3400 RPM'
Peak Torque . . . . . . . . . . . . . . . . . . . 380 lb . ft . C 1700 RPM"
Comp. Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 .5 :1
1200 1600 2000 2400 2800 3200 3600
ENGINE SPEED - RPM
POWER OUTPUT AT SAE J1349 conditions
Figure 7-5 -Typical 6.51- Turbocharged Engine
Ratings and Specifications
'HP and Torque range from 140HP/255 Ib . ft . to rating on chart . Combustion chamber . . . . . . . . . . . . . . . . . . . Indirect injection
Turbo boost . . . . . . . . . . . . . . . . . . . . . . . 10 psi @ peak torque
Turbo mfgr. . . . . . . . . . . . . . . .. . . . . . . . . . . . . Borg Warner/11-11
Performance Curve RPO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L65 H.D . engine
300 Performance Curve
280
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POWER OUTPUT AT SAE J1349 conditions
GM's 6.51. V8 TURBO DIESEL
ENGINE
Turbocharged
The 6.5L features a completely integrated Borg Warner/IHI
turbocharger. This turbocharger is waste-gated on the
exhaust side of the turbo with an all-new wastegate that is
patented by GM and is specifically designed for this
system. This new wastegate provides very tangible benefits.
By design, it reduces overall stress on the internal
engine components . To accomplish this, the wastegate is
designed to reduce turbo-boost pressure after maximum
torque is obtained . This turbocharger delivers a top-boost
of 10 psi at 1700 RPM and produces outstanding responsive
acceleration on demand with no detectable turbo-lag .
Crankshaft Bearing and Seal
The crankshaft bearings used in the 6.5L are made of a
more fatigue resistant bearing material . This material
promotes a higher stress life of the bearings. The rear
crankshaft seal is a one-piece seal that greatly reducesthe
chances of leakage.
Fuel Filtration System
SECTION 7D - ENGINE FUEL SYSTEMS
The double filtration fuel filter on the 6.51- combines the fuel
filter, water separator and fuel heater all in one canister. Its
location and top-load vertical design allows easy filter
cartridge replacement.
New Piston Design
The 6.5L bulkhead area was designed to handle the higher
cylinder firing pressures of a turbocharged engine. In addition
the coolant passages and the oil galleries were sized
to provide the increased flow required by a turbo engine.
Serpentine Belt Drive
The 6.51- features a single serpentine drive belt with an
automatic tension adjuster which improves belt life. The
system maintains the desired belt tension needed to run
the integral components while allowing for the easy
replacement.
Water Separator Draincock
As the water separator is an integral part of the fuel filter on
the 6.5L, the method of draining off the water has been
designed for convenience . The water separator draincock
has been located up front on the top of the engine, allowing
for easy draining when required .
Optimized Combustion Chamber
To provide smokeless performance and to meet stringent
emissions standards without sacrificing power, the 6.51-
was designed with an optimized combustion chamber. This
design provides an optimum balance of air in the prechamber
in the head and of air in the cylinder. This balance
of air enhances a more even and complete burning of the
fuel.
Horsepower & Torque
The 6 .5L Turbo Diesel has a horsepower rating of 190
3400 RPM and a torque rating of 380 Lb.-ft. @ 1700 RPM,
and provides a 30% torque rise over a usable 2800 RPM
range.
EXHAUST MANIFOLDS
SECTION 7
There are three types of materials used in the various
years and models of the G- and P-Series motor home
chassis. Each material described below has specific features
and drawbacks to be considered before being selected
by the design engineer.
" CAST IRON-Cast iron has been used for many years
for the 454 CID engines including some current year
engines. Cast iron is good for its ability to withstand
heat and it is easy to produce and machine. However,
a drawback to using cast iron a$ an exhaust manifold
is that it can crack easily and has a slight tendency to
warp.
NODULAR IRON - Nodular iron has been used on
many 350 CID and 454 CID engines . The nodular
manifold is 5/16 in. thick versus 3/16 for the cast
iron. Nodular iron has some of the same properties
of cast iron but is not as prone to cracking. Also,
nodular iron has less tendency to warp and become
distorted than conventional cast iron.
" STAINLESS STEEL - Stainless steel had come into
use with some past production 454 CID engines
with the new emissions Systems. Starting in 1985
midyear through 1989 federal and 1989 California. It
is very difficult to produce and the materials cost is
high. The net result is that the total cost of using
stainless steel manifold vs. the manifold cast family
itself is extremely high.
With any manifold, the extremes of use are great. At one
moment the manifold is 40 degrees Fahrenheit below zero
and a few minutes later the manifold itself is white hot .
Or, the manifold is white hot and the vehicle goes through
a water puddle and quenches the manifold . Any and all
parts can withstand a given amount of cycles or use before
failure. GM warrants exhaust manifolds as part of . the
normal, published warranties with the realization that it is
very possible to produce a defective manifold . However,
in instances where repetitive failures occur, the owner and
service technician should examine the actual applications
of use as to the cause of the failure (i .e ., overload, road
splash, poor air flow, incorrect bolt torque, incorrect parts
or improper installation) .
NOTE: Experience shows that installing exhaust
manifold gaskets rather than resurfacing the
manifold is only a short time repair . Leaking
manifolds should be resurfaced or replaced
and do not use a gasket but use anti-seize
compound #1052771 to increase manifold life.
SERVICE TIPS
NODULAR IRON MANIFOLD SHRINKAGE
At times a service technician may experience a problem
with replacement of a manifold after it has been removed
for service . The technician is unable to reinstall the attaching
bolts due to shrinkage of the manifold. This complaint
is a result of heat present at the time the manifold
7-3
ENGINE
was removed. The more heat present when the manifold
is removed, the greater the "apparent" shrinkage of the
manifold .
The manifold may be installed in the following manner:
1 . Install the two (2) center attaching bolts and torque the
bolts to 10 ft. lbs. Install additional bolts if alignment is
possible.
2. Connect the exhaust pipes, crossover pipe, etc . to allow
the engine to "run."
3. Start the engine and allow the engine to run (5 to 12
minutes) until the manifold expands allowing easy installation
of the remaining bolts.
4 . Torque the center bolts to a full 40 ft, lbs . torque and
apply slightly less torque for each bolt as you proceed
toward each end. (See Cast Iron Manifold Cracking
section below for additional information .)
NOTE: This procedure is not considered detrimental to
the exhaust manifold in any way and can be used
to save the expense of a new manifold.
CAST IRON MANIFOLD CRACKING
Before installing a new manifold, the dowel pin holes
and bolt holes should be increased 1/32 inch in
diameter to enable the manifold to expand and contract
without buckling . The reason for this is that in
some of the larger engines, the manifold actually increases
in length as much as 1/8 inch when going from
atmospheric temperature to operating temperature .
Apply a liberal amount of anti-seize compound
#1052771 to the manifold face and head face to increase
manifold life. The compound appears to create
a hard slate-like film with a very low coefficient of friction
allowing the manifold to expand and contract and
can be purchased through any Chevrolet dealership
parts department.
When installing a manifold on 454 engines, torque the
center bolts to a full 40 ft. lbs . torque and slightly less
torque for each bolt as you proceed towards either end .
NOTE : If the bolts are not tightened enough, leaks will
occur. If the bolts are overtightened, the manifold
cannot expand and will buckle. Use a torque
wrench whenever possible.
CAST IRON WARPING
Often times a warped cast iron manifold is caused by
loose, poorly torqued attaching bolts or a broken attaching
bolt. If the manifold is not held firmly against the block for
proper heat absorption, exhaust heat can add to a warpage
problem. The repair procedure may not require the
manifold to be replaced providing a quality machine shop
can resurface the face of the manifold flat. This can be
an advantage as the cast iron has been "cured" with many
heatings and coolings. Remachining the surface flat may
actually be a better repair than manifold replacement.
SECTION 7
EXHAUST MANIFOLD AND PLUG
WIRE FAILURE
Chevrolet has determined that right side exhaust manifold
and right side spark plug wire failure may be the result of
inadequate air flow. This is due to the absence of a wheelwell
panel on the right front wheel opening. This situation
allows necessary engine cooling air flow to exit the engine
compartment prior to passing the exhaust manifold and
spark plug wires and therby cooling the manifold and
spark plug wires as occurs on the left side of the engine
compartment. See Figure 7-4.
Figure 7-4 - Inadequate Engine Compartment
Air Flow
This condition can be corrected by fabricating a metal
panel similar to the one used on the left side of the vehicle .
Adding the panel forces the air flow to pass along the right
side of the engine compartment therby providing a cooling
effect and greatly extends the manifold and spark plug
wire life. See Figure 7-5 .
Figure 7-5- Corrected Engine Compartment Air Flow
NOTE: Installation of the right hand engine heat splash
shield GM Part #15680348 was implemented on
7-15-92 VIN #321432 see Figure 7-6-C.
ENGINE
Care must be taken in the design of the right side panel
as to provide proper clearances around any hoses, wires
and engine dress items and also to provide clearance for
the tire throughout its movements. The panel should extend
rearward to a point parallel to the number seven
spark plug wire. The panel should be shaped and positioned
similarly to the left side panel currently installed on
the vehicle . Care must be taken to leave an opening at
the rear of the engine compartment to allow cooling air to
exit the engine compartment as on the left side panel .
See Figure 7-5 .
The motor home owner should be advised that when stopping
the vehicle for fuel fill or rest stops after sustained
highway driving, the engine should be allowed to idle for
a period of three to five minutes before turning off the
engine. This "idle time" allows the cooling fans enough
time to reduce and stabilize the underhood temperature
thereby increasing effective component life (spark plug
wires, exhaust manifolds, belts, hoses, etc .).
EXHAUST MANIFOLD LEAKS
The following information is provided as an aid to the
motor home owner of vehicles experiencing difficulty of
both right and left exhaust manifold leaks. The information
has been extracted from a Chevrolet Dealer Service Bulletin
and intended to be used in conjunction with the right
panel air flow correction described above.
Reference: Chevrolet Dealer Service Bulletin
No. 86-255 (November, 1987)
`Some 1981-86 vehicles with 7.4L engines and cast iron
manifolds may experience a condition where an exhaust
leak develops between the manifold and the cylinder head
mating surface causing a "noise condition ."
Starting in 1987, an improved cast iron exhaust manifold
using nodular iron instead of grey iron was released on
the 1987 RV vehicles with the 7.41- engine. The nodular
iron manifold is less susceptible to heat warpage than the
previously used grey iron exhaust manifold . This manifold
can be used to repair leaking exhaust manifolds on earlier
year trucks and motor homes. This manifold is NOT interchangeable
with tubular manifolds used with the H5D
(Federal Emissions NA5/NA6 equipped trucks built after
July 1, 1985, with Heavy Duty Emissions and dual air
pumps) emission system .
NOTE: To Install the improved manifold, parts in
Figure 7-6-A are required .
SECTION 7
Figure 7-6 - Typical Manifold
NOTE: A recent study by our engineering department
has revealed that a substantial increase in exhaust
manifold life can be obtained by cutting
the manifold attaching support in 3 places between
bolts #2 & 3 and 4 & 5 and 6 & 7 with a
metal saw which allows each runner to move
independently. See Figure 7-6.
Figure 7-6-A
7-5
ENGINE
LEFT EXHAUST PIPE TO ENGINE OIL
FILTER INTERFERENCE
The following information was extracted from a Chevrolet
Dealer Service Bulletin relating to left exhaust manifold
header pipe redesign .
Reference: Chevrolet Dealer Service Bulletin
No. 86-250 (September, 1987)
Some 1985-86 P-3 models equipped with a 7.4L engine
and H5D emissions may exhibit a situation where the
left exhaust manifold pipe contacts the oil filter. This
condition was corrected (effective S.O.P. 1987) with
the release of a redesigned exhaust manifold pipe. See
Figure 7-6-B. This new pipe provides increased
clearances between the oil filter and the exhaust pipe.
This new exhaust manifold pipe may be obtained through
GM-SPO (GM Part No. 15559924) and may be used on
earlier production vehicles manufactured with a 7.4L engine
and H5D emissions .
Figure 7-6-B - Redesigned Left Exhaust Manifold Pipe
Figure 7-6-C
PARTS INFORMATIONIMPROVED
CAST IRON MANIFOLD
GM PART NO. USAGE QUANTITY.
14103191 Manifold-Exhaust LH 1
10045732 Manifold Assembly- 1
Exhaust RH
14053573 Stud-Exhaust 3
Manifold LH
14053574 Stud-Exhaust 3
Manifold RH
587575 Spring-Exhaust 6
Manifold
9422297 Nut-Exhaust 6
Manifold (3/8-16)
120395 Washer-Exhaust 6
Manifold (3/8-Flat)
15592451 Seal Assembly- 2
Exhaust Manifold
3909821 Bolt-Exhaust 16
Manifold
(3/8 x 1-3/16)
10017198 Plug-Oxygen Sensor 1
(18mm) LH Side
5617102 Gasket-Oxygen 1
Sensor Plug LH Side
10068600 Shield-Starter 1
9439915 Nut-Starter Shield 2
(114-20)
1052771 Anti-seize Compound 1
NOTICE : THE RIGHT HAND MANIFOLD
ASSEMBLY INCORPORATES A
SHORTER HEAT STOVE. TO
PROTECT STARTER WIRING, A HEAT
SHIELD (GM PART NO. 10068600)
MUST BE INSTALLED.
SECTION 7A
GENERAL DESCRIPTION
The oil pan acts as a reservoir for holding the oil waiting
to be circulated through the engine. The oil pan is attached
to the bottom side or pan rail of the engine.
A pressure-feed type pump is mounted to the bottom side
of the rear main bearing cap.
Extending down from the pump and into the oil, is a pickup
tube with a screen cover to filter out foreign material.
Oil is picked up by this tube and pumped through the
gear-type oil pump. In the gasoline engines, the distributor,
driven by a helical gear on the camshaft, drives the
oil pump. For the diesel engine, the pump is driven from
the engine camshaft by means of an intermediate shaft.
The oil is next pumped from the engine and through a
cooler located in front of the radiator which cools the oil
and thus helps to remove engine heat (Figure 7-7).
From the filter, the oil passes through a cooler. If this fullflow
filter becomes clogged, the engine is equipped with
a bypass valve which is spring loaded. This valve protects
the engine from oil starvation byopening when increased
ENGINE LUBRICATION
ENGINE LUBRICATION
Figure 7-7-Typical Engine Oil Cooler Installation- Mark IV-1986 and Earlier
7-6
pump pressure tries to pump oil through a clogged filter .
When the pressure causes the bypass valve to open, the
oil bypasses the filter and the engine continues to receive
lubrication . Replacement of the filter at proper intervals
will prevent damage to the engine due to a clogged filter .
From the filter, the oil is pumped through the drilled galleries
in the case to the various moving metal parts in the
engine. After being pumped to the critical engine parts,
oil drains back to the crankcase. Also, as the crankshaft
rotates it slings oil off the crankpins to cover cylinder wall
pistons, piston pin and piston rings. Oil drains off these
parts and back to the engine pan.
There is also a second bypass valve. This is the oil-cooler
bypass valve. It works much the same as the oil filter
bypass valve and opens to allow an alternate route for
the oil if the cooler should become clogged .
There is an oil pressure switch which is assembled to the'
top rear of the cylinder block to sense oil pressure in the
main gallery .
RADIATOR
OIL FILTER
ENGINE
OILS
QUALITY
Engine oils are labeled on the containers with various API
(American Petroleum Institute) designations of quality. For
gasoline engines, Chevrolet recommends the use of an
oil with the API designation "SG," either alone or shown
with otherdesignations such as "SG/CC." Oilswhich are
not labeled "SG" should not be used. Fordiesel engines,
Chevrolet recommends the use of oil designate of
"SG/CE" or "SG/CD." Other designations including
"SG" alone should not be used for diesel engines . Using
oils of a quality other than those recommended for
Chevrolet gasoline and diesel engines respectively
could cause engine damge.
VISCOSITY
SECTION 7A-ENGINE LUBRICATION
Engine oil viscosity (thickness) has an effect on fuel economy.
Lower viscosity engine oils can provide better fuel
economy; however higher temperature weather conditions
require higher viscosity engine oils for satisfactory
lubrication . Using any viscosity oils other than those
recommended could cause engine damage.
When choosing an oil, consider the range of temperature
your vehicle will be operated in before the next oil change.
Then, select the recommended oil viscosity from the applicable
chart shown in Figure 7-8 or Figure 7-9 .
GASOLINE ENGINES - For temperatures above 0°F,
SAE 10W-30, is preferred for a single-choice multi-viscosity
oil. However, for heavy-duty expressway driving in
summer temperatures, there can be an advantage to a
single-viscosity straight SG/CD 30 oil .
NOTE : 10W-40 is missing from the chart shown in Figure
7-8. 10VV-40 has been removed from all GM recommendations,
because GM Research Labora
tories have found generally a 1 .2% fuel economy
penalty compared to 10W-30. Of the oils surveyed,
some contained inadequate additives or
even no additives and some did not meet the
10W-40 viscosity requirements. GM testing
showed 10W-40 oils tended to be more prone to
high mileage ring sticking. These problems appeared
more frequently in 10W-40 oils than in
10W-30 oils.
As a rule of thumb, in heavy-duty applications and sustained
high-speed expressway driving, a single viscosity
grade oil such as SAE 30 will be more satisfactory than
multi-viscosity oils such as SAE 10W-30. Multi-viscosity
oils have an advantage of cold weather starting ease and
better initial lubrication with cold engine oils.
Notice that on the temperature chart shown in Figure
7-8, there is a trend away from the thinner viscosities as
temperature goes up. The reason is that light oils do not
have enough body for heavy-duty loads and high
temperatures .
Hot
Weather
Cold
Weather
Figure 7-8- Oil Viscosity Chart-Gasoline Engine
DIESEL ENGINES - For temperatures above 32°F,
SAE 15W-40 is the preferred viscosity grade. SAE 30 oil
can be used for continuous daily driving and all driving
where the temperature will not be less than 32°F.
These oils combine excellent film strength with the
best available additive package to prevent wear and
protect against piston ring sticking at higher mileages.
DO NOT USE SAE 10W-40 oils in diesel engines,
because most of them can cause piston ring sticking
and engine damage.
SAE 30 SG/CE and SF/CD oils are generally not suitable
when temperatures fall below 32 0 F because of cold
starting considerations. The use of SAE 15W-40 SG/CE
or SF/CD at these lower temperatures (and in extremely
cold areas SAE 10W-30 SG/CE or SF/CD) may be
necessary.
Hot
Weather
+60
+32
0
-20
Cold
Weather
,C .
+38
0
-18
-2s
SAE IoW-30
Figure 7-9- Oil Viscosity Chart- Diesel Engine
7-7
TEMPERATURE
ENERGY CONSERVING OILS
SYNTHETIC ENGINE OILS
SECTION 7A - ENGINE LUBRICATION
Study the chart shown in Figure 7-9 carefully and follow
its recommendations. As always, NEVER exceed the recommended
oil change intervals since oil quality deteriorates
rapidly with mileage, as carbon accumulates in the
oil.
SG/CD oils have generally proven to be the most successful
oils in diesel applications . The diesel combustion
process tends to produce sticking piston rings
and high-sulfur fuels create problems that SG/CD
chemistry is best suited to correct . Purchase fuels
with a sulfur content of less than 0.4%. When sulfur
content raises to between 0.4% and 1 .0%, it is a good
practice to change oil at one-half the normal interval .
When fuel sulfur content is above 1 .0%, oil should be
changed at one-fourth the normal interval .
SG/CE oils are generally best suited to gasoline
engines . Gasoline engines do not have to cope with
much of a sulfur problem and rarely develop ring sticking
problems with proper oil change intervals . Gasoline
engines, because of their temperatures and flat tappet
cams, need oils of superior anti-wear properties and the
SG/CE chemistry is much better for this application .
Normal engine lube oil temperature in a heavy-duty truck
engine is between the engine water temperature and 50
degrees above coolant temperature. When the temperature
of the engine lube oil exceeds the temperature of
the engine coolant by more than 50 degrees the engine
lube oil cooler is not doing its job properly and requires
immediate attention . Severe oxidation problems will occur
to lube oils that are subjected to high heat and extended
oil change intervals.
The oxidation rate of lube oils doubles with each 20 degrees
of increase in lube oil temperature. Also, oxidation
occurs in lube oil that is not being used or is in storage.
Figure 7-10 indicates the expected oxidation rate of a lube
oil containing a moderate amount of oxidation inhibitor
under temperature increases of 20 degrees .
It is recommended that you select an oil not only of the
proper quality and viscosity, but also a fuel-saving product.
These oils can be found in dealer service departments,
service stations and other retail stores. They are
identified by words such as: "Energy Conserving," "Energy
Saving," "Conserves Gasoline," "Gas Saving,"
"Gasoline Saving," "Friction Reducing," "Improved Gasoline
Mileage," "Improved Fuel Economy" or "Fuel Saving,"
etc . Be sure the fuel-saving oil you choose is of
the recommended viscosity and API designations.
Some fuel-saving oils do not meet the requirements necessary
for your vehicle's engine .
Synthetic engine oils and conventional, mineral-oil-based
engine oils have some similarities . They are both blends
7-8
Figure 7-10-Temperature vs. Oil Life Expectancy
of base oils and additives . In fact, most of the additives
used in synthetic engine oils, are identical to those used
in conventional engine oils; in at least one so-called synthetic
oil, mineral oil is used as the base.
The mineral oil used in conventional engine oils is a mixture
of hydrocarbons (hydrogen and carbon) obtained
from crude oil pumped from the ground and refined by
physical separation processes such as distillation and solvent
extraction. The base oil used in most synthetic engine
oils is obtained by chemical reaction processes involving
materials produced from the same crude oil . For example,
an acid and an alcohol can be obtained from crude oil
and reacted to produce an ester - a commonly used
synthetic base oil - which is a fluid composed of hydrogen,
carbon and oxygen.
The performance quality of a finished engine oil, either
conventional or synthetic, depends on a careful selection
of the base oil and additives to produce the desired
characteristics.
Chevrolet currently recommends the use of SG engine
oil only. To determine whether an oiI meets SG quality requirements,
engine dynamometer tests (called Sequence
Tests) are run which evaluate the ability of the oil to prevent
wear, deposits, and rust and corrosion, as well as
thickening of the oil itself.
The Sequence Tests have been carefully developed over
many years to ensure that an SG engine oil will perform
satisfactorily in car engines under a wide variety of service
conditions. Oil change intervals are selected based on
many miles of car test and field service experience . Oil
quality, engine design, type of service, and change interval,
must be carefully balanced to ensure satisfactory
engine performance and durability. The current recom-
DEGREES F LIFE EXPECTANCY
70 100 years
90 50 years
110 25 years
130 12 years 6 months
150 6 years 3 months
170 3 years 1 .5 months
190 570.70 days
210 285.35 days
230 142.67 days
250 71 .33 days
270 35.66 days
290 17.83 days
SECTION 7A
mended oil change intervals apply to any SG engine
oil, conventional or synthetic.
Information currently available on synthetic oils does not
justify. any additional lengthening of the oil change intervals.
Any engine part failures caused by using an oil beyond
the recommended change intervals will not be
covered under the New Vehicle Warranty .
MAINTENANCEAND INSPECTION
To provide proper lubrication for the engine and to help
prevent engine damage, the oil level should be checked
periodically to ensure that there is an adequate amount
of oil . Also, the engine oil must be drained and replaced
with fresh oil, and the oil filter replaced at the intervals
recommended in the appropriate Maintenance Schedule.
CHECKING OIL LEVEL
" Warm - The best time to check the engine oil level is
when the oil is-warm, such as during a fuel stop. First,
allow a minimum of 10 minutes for the oil to drain back
to the oil pan. Then pull the dipstick out, wipe it clean
and push it back down all the way.
NOTE: Failure to allow sufficient time for the oil to drain
back into the oil pan can give an erroneous "low
oil" reading and the appearance of excessive oil
consumption . This applies to both gasoline and
diesel engines. Approximately 10 minutes are required
for full drain-back. NOTE :
Pull the dipstick back out and look at the oil level on the
dipstick . Some dipsticks are marked with "Add" and "Full"
lines. Others are marked "Add 1 Qt." and "Operating
Range." In all cases, keep the oil level above the "Add"
line. Push the dipstick back down all the way after taking
the reading. Add oil if needed.
" COLD -- If you check the oil level when the oil is cold,
do not run the engine first. The cold oil will not drain
back .to the pan fast enough to give a true oil level.
A good method of checking oil is as follows : At the end
of a day's driving, pull the dipstick out slightly from the
tube so that the tube is not sealed by the cap at the top
of the dipstick . Leave the dipstick in this position overnight .
Before starting the engine again the following day, seat
the dipstick and check the oil level. This method will allow
the oil to drain down easily and provide a more accurate
reading.
CHANGING THE OIL
Oil can be-drained from the engine through the drain hole
in the bottom of the oil pan. Replacment oil is added
through the fill tube at the top of the engine and near the
radiator. Generally, the recommended oil change interval
for heavy-duty service is 3,000 miles. More frequent intervals
are recommended if any of the following severe
operating conditions are encountered:
" Frequent long runs at high speeds and high ambient
temperatures
ENGINE LUBRICATION
7-9
" Operating in dusty areas
" Towing a trailer or car
" Idling for extended periods and/or low-speed operation
" Operating when outside temperatures remain below
freezing and when most trips are less than 4 miles (6
kilometers) .
NOTE: Refer to the owner's manual and vehicle Maintenance
Schedule for the oil type, viscosity and
alternate change intervals recommended for the
operating conditions encountered.
CHANGING THE OIL FILTER
The oil filter is a spin-on type which can be removed with
a band-type filter wrench . The replacement filter should
be installed and hand tightened following the instructions
with the filter.
454 ENGINE OIL FILL CAPACITY
The 454 engine used in the motor home has a crankcase
capacity of six (6) quarts plus one (1) quart for the ACPF35
oil filter for a total of seven (7) quarts. The seven
(7) quart system has been in place for many years.
After an oil and filter change, an incorrect dipstick
reading could occur showing an overfill. Chevrolet
has determined the problem to be in the dipstick
and/or tube calibration . Through the process of
converting to metric, several different parts
sources, and some stack-up and assembly tolerance,
it is difficult to fully understand the problem.
Chevrolet has determined that there is not
a durability problem with operating the seven (7)
quart system down as much as two (2) quarts.
Nevertheless, to comply with the original design
criteria and for other technical reasons, it is recommended
you verify the dipstick calibration .
An accurate procedure is as follows :
1 . Drain the engine oil when hot and remove the oil
filter. Allow 10 minutes for complete drain.
2. Install a new AC-PF35 oil filter and 6 quarts of oil.
3. Start engine and run 5 minutes and shut off and
allow 10 minutes for oil to drain down from the
heads.
4. Dipstick the engine 3 times, and with a small file,
make a mark at the fluid edge in the dipstlck that
will indicate the new "add oil" mark.
5. Add 1 quart of oil, let set 5 minutes and again
dipstick the engine 3 times and make a mark at the
fluid edge which will indicate the full mark.
SECTION 7A
DIPSTICK REPLACEMENT
Some owners of the 1987 P-30 motor home chassis with
7.4L carbureted engines may realize problems with the
oil level indicator (dipstick) assembly. Problems include
(1 .) the oil level indicator is difficult to reinstall or (2.) the
gage shows an incorrect oil level.
ENGINE LUBRICATION
If these conditions are encountered, they can be corrected
by replacing the oil level indicator (GM Part No .
10085674) . The new oil level indicator incorporates a "T"
handle on the end and'a twist on the shaft making it easier
to install, and the new indicator has relocated oil fill level
markings.
APPENDIX 7-1
GUIDELINE FOR ENGINE OIL
CONSUMPTION
The following information has been provided as a guide
to the motor home owner concerning engine oil consumption.
GM has produced the following guideline based
upon information developed by Detroit Diesel .
Many attempts have been made byvarious manufacturers
to establish how much oil consumption can be expected
by the owner. Detroit Diesel established a series of charts
that took individual engine families from the smallest to
the largest . As an example, the smallest engine family
(2-71) operating at 2,100 RPM could be expected in a
10-hour working period to use about one-half quart of oil:
The largestengine normally used in stationary application
(about seven feet high by nine feet long in an engine
stand) is d 16-cylinder engine (called a 16V-71T) that
normally uses 8 or 9 quarts of oil at 2,300 RPM in a 10-
hour working period. In a stationary application, a very
accurate prediction can be made, because the engine
generally runs at a given RPM, is of a known size and is
doing a given task, so the operator can easily use the
charts.
Charts could be produced for gasoline engines just as
well, but generally in the automotive industry most applications
are not stationary uses. Rather, the normal highway
usage includes everything from idle, to wide-open
throttle, to pulling a trailer . You have learned from the
Detroit Diesel information that the bigger the engine and
corresponding horsepower the greater the thirst for oil and
petroleum products . For the standard automotive application,
General Motors has developed a graph illustrating
the relationship between minimum acceptable engine oil
consumption and fuel usage. (See Figure A7-1-1 .) Engines
with oil consumption below the level indicated by
the "acceptable" line are potential candidates for repair .
Note that engines working harder, i .e. using more fuel,
will have higher oil consumption . Heavy-duty trucks, for
example, will not achieve the same level of oil economy
as passenger cars and, therefore, should not be considered
for repair at the same levels .
10 15 20 25
FUEL MPG
(MILES PER GALLON)
- i MARGINAL OIL
CONSUMIJTION
- DIFFICULT TO DIAGNOSE /
- POSSIBLE CAUSE:
EXTERNAL LEAKS,
MALFUNCrI01NING PCV /
SYSTEM
* MISSING, WORN OR
MISLOCATED VALVESTEM
SEALS
-HIGH OIL CONSUMPTION
-CAUSE NORMALLY IDENTIFIABLE
-MAY INVOLVE
0 ANY OF THE ABOVE
*PISTON, PISTON RING, OR BORE'
SCORING OR WEAR
" VALVE GUIDE SCUFF OR WEAR
" MISSING OR BROKEN RINGS
30 35
Figure A7-1-1- Engine Oil Consumption vs. Fuel Usage
7-11
The graph shown in Figure A7-1-1 does not consider time
as a factor, however, two time-related factors are involved:
(1 .) Judgements of excessive oil consumption should not
be made until the engine is fully broken in (approximately
5,000 miles) and (2.) A sudden or significant change in
oil consumption (when operating conditions remain the
same) should be considered when deciding if repair is
justified .
Engines with very high oil consumption normally have
obvious, easily diagnosed causes. Scuffed bores, broken
or overlapped rings, or worn valve guides or seals are
typical examples.
Engines with marginally high oil consumption (indicated
by the darkened section of the graph in Figure A7-1-1)
are very difficult to diagnose even after disassembly. In
these cases, initial efforts to correct the complaint should
be directed at replacement of easily accessible items like
gasketed areas with heavy leakage, PCV valve or oil separator,
or valve stem seals, and verifying that the owner
APPENDIX 7-1
GUIDELINE FOR ENGINE OIL
CONSUMPTION (Cont'd)
is using the best weight engine oil for the operating temperature
before starting heavy repair in the piston ring and
bore area.
Manufacturers of power piston rings state that piston rings
in today's engines, control oil very effectively. If 1/10th of
a drop of oil would be consumed per explosion when
driving at 60 MPH, an eight-cylinder vehicle would use
about 90 quart§ of oil on a 600-mile trip. The actual average
consumption of oil per explosion in today's engines
is from 1/1,000th to 2/1,000th of a drop.
NOTE: If a service technician determines that your engine
valve seals need replacement, the recommended
seals for the 454 engine are the
Orange VITON engine seals (GM Part No.
460527). VITON is an extremely good material
for heavy-duty usage and is standard in the 454
& 427 truck engine.
SECTION 7B- ENGINE COOLING SYSTEM
ENGINE COOLING SYSTEM
GENERAL DESCRIPTION
To remove the excess heat from the engine and to maintain
normal engine operating temperatures, both of the
gasoline engines, and the 6.21- diesel engine use liquid
cooling systems . Components of a typical system include
a pump, thermostat, radiator, coolant recovery tank and
hoses.
In operation, the pump circulates coolant through passages
in the engine cylinder block and heads ,where it
absorbs heat. The hot coolant flows out of the engine
through a hose to the radiator . In the radiator, the coolant
loses heat to the outside air circulating around the radiator
core tubes. Cooled coolant then flows out of the radiator,
through a hose back to the engine.
The engines have pressure-type cooling systems with
thermostatic control on coolant circulation . The cooling
system is sealed by a pressure-type radiator filler cap
which causes the system to operate at higher-thanatmospheric
pressure.
The higher pressure raises the boiling point of the coolant
which increases the cooling efficiency of the radiator . The
15-pound pressure cap used raises the boiling point of
coolant to approximately 262°F at sea level .
All models have a closed cooling system using a round
pressure cap (Figure 7-11) and a coolant reservoir . Coolant
can be added without removing the radiator cap.
Figure 7-11- Radiator Pressure Cap
A pressure-vacuum valve radiator cap (Figure 7-11) is
used. As the engine warms up, pressure is developed due
to the temperature expansion of the coolant . When pressure
reaches the preset cap value (usually 15 PSI), the
big spring compresses and the large gasket contacting
the radiator neck unseats and allows the surplus coolant
and air to flow into the coolant overflow tank. As the system
cools upon shutdown, the coolant shrinks in volumetric
size creating a partial vacuum in the radiator . This
partial vacuum overcomes a small hidden spring and the
very center relief valve of the cap unseats. Consequently,
coolant from the overflow tank returns to the radiator to
start the process over again .
7- 1 3
Using the pressure relief cap in conjunction with the
overflow tank, the design intent is to assure a 100 percent
filled radiator at all times with any air or bubbles being
pushed out of the radiator into the overflow tank. However,
if the coolant level is too low initially, the cycle between
the system and reservoir will not take place.
THERMOSTAT
The thermostat consists of a restriction valve actuated by
a thermostatic element to help regulate the operating temperature
of an engine. This is mounted in the forward part
of the intake manifold, under the coolant outlet on the 5.71-
and Mark IV gasoline engines and in the coolant crossover
pipe located at the front of the engine on the 6.21- diesel
(Figures 7-12 and 7-13) . Thermostats are designed to
open and close at predetermined temperatures.
Figure 7-12- Coolant Thermostat Location --
7.4L Mark IV Gasoline Engine
All Chevrolet engines have a pellet-type thermostat
(Figure 7-14) which is used in the coolant outlet passage
to control the flow of engine coolant . It provides fast engine.
warm-up and regulates coolant temperature levels . A wax
pellet or power element in the thermostat expands when
heated and contracts when cooled. The pellet is connected
through a piston to a valve. When the pellet is
heated, pressure is exerted against a rubber diaphragm
which forces the valve to open . As the pellet is cooled the
contraction allows a spring to' close the valve. Thus, the
valve remains closed while the coolant is cold, preventing
circulation of coolant through the radiator, but allowing the
coolant to circulate through the engine to warm it quickly
and evenly.
SECTION 713-ENGINE COOLING SYSTEM
Figure 7-13 - Coolant Thermostat Location-
6.21. Diesel
FLANGE PISTON
COIL SPRING
WAX PELLET RUBBER DIAPHRAGM
Figure 7-14- Thermostat- Typical
As the engine becomes warm the thermostat pellet expands
and the thermostat valve opens, permitting the
coolant to flow through the radiator where heat is passed
through the radiator walls. This opening and closing of
the thermostat valve permits enough coolant to enter the
radiator to keep the engine operating temperature above
the lowest operating value stamped on the thermostat.
The engine thermostat is often the first item that is suspected
and replaced when the engine overheat condition
is encountered. The thermostat is only designed to keep
the engine operating temperature above the thermostat
minimum or rated temperature. It has no way to control
temperature above this. If an engine is overheating, replacing
a thermostat rated at 195°F with one rated at 165°F
7-1 4
would not reduce the maximum operating temperature 30
degrees . If an engine is overheating, it is obviously operating
above both 165 and 195 degrees Fahrenheit.
ENGINE COOLING FANS
Both the 5- and 7-blade engine cooling fans tend to be
very noisy and draw a lot of horsepower. By varying the
fan speed, both horsepower losses and noise are lowered
except in maximum cooling demand situations. According
to numerous industry tests, maximum cooling is required
less than five percent of the total vehicle time. With the
fan operating on low speed 95 percent of the time, there
is a reduction in noise level and substantial savings in
fuel.
The fan should be viewed as a two-speed fan - low and
high speed . When in the hi-speed mode, the noise level
will be more than double . Noise levels are somewhat logarithmic
in nature. Viscous drive fans always provide
some air flow across the radiator and air conditioning . This
type of fan drive also helps maintain design temperature
differential between inlet temperature and outlet temperature
to a 10°F and 15°F differential at maximum engine
speed and load. Good cooling system design avoids excessively
cold coolant from going back into the bottom of
the block. School bus engines will sometimes have heat
shock problems because in addition to the radiator there
are as many as four or five heater-and-defrosters and very
long lines removing large amounts of heat from the coolant
above and beyond the radiator capacity.
The variable drive fan is controlled by a temperature-sensitive
clutch . (See Figure 7-15 .) The clutch housing is
constructed of lightweight metal which is filled with silicone
oil and hermetically sealed.
Thermostat control of the fluid clutch permits the fan to
operate only when additional air flow is required to reduce
radiator coolant temperatures . During periods of operation,
when radiator discharge air temperature is low, (be--
low approximately 150°F), the fan clutch limits fan speed
to 800-1,400 RPM. At this RPM, the clutch is disengaged
since a 'small oil pump, driven by the separator plate,
forces the silicone oil into the reservoir between the separator
plate and the front cover assembly. Also the passage
from this cavity to the clutch area is closed by a
sliding valve. (See Figure 7-16, Line A.)
As operating conditions produce a high radiator discharge
air temperature (above approximately 150°F), the
temperature-sensitive bimetal coil tightens to move the
sliding valve plate, allowing the flow of silicone oil into the
clutch chamber to engage the clutch, providing maximum
fan speed of approximately 2,200 RPM . (See Figure
7-16, Line B .)
The clutch coil is calibrated so that with a road load at an
ambient temperature of approximately 90°F, the clutch is
at a point of shifting between high and low fan speeds.
SECTION 7B -ENGINE COOLING SYSTEM
Figure 7-15-Engine Cooling Fans
NOTE: The 2nd design was interim 1988 to 4-1-89. The 3rd design started 4-2-89. Part #15643265 stamped RL -
the clutch is engaged at all speeds to help reduce the radiator temperature and fan noise. It engages only
the amount required to keep the radiator within the operating temperature.
PASSENGER CARS, LIGHT-DUTY TRUCK
AND MOTOR HOMES
4500
4000
3500
0 3000
a 2500
zQ 2000
1500
1000
500
INPUTSPEED = N'
00
Figure 7-16- Typical Speed andTemperatureModulations
I/ .
/
I
/ o IW
y
l w
I w
I Wz
f I la
ll!
Z4 I~
ENGAGED AN SPEED
I
I
N' = Nf (FAN SPEED
FAN DRIVE)
WITHOUT
ME,
ONE .
MEN
.
B PP_
ONNE
Fur
0 1000 2000 3000 4000 50
In extreme high temperature for rescue and multi-stop
delivery vehicles or winter snowplow applications where
the snow blade interferes with air flow, disconnecting the
fan clutch thermostat control increases air flow through
the radiator by allowing the fan speed to more closely
follow engine speed until approximately 2,000 RPM.
SECTION 7BNo
attempt should be made to adjust the calibration of
the engine fan clutch assembly as each assembly is individually
calibrated at the time of manufacture.
To disconnect the bimetal coil spring thermostat on Eaton
and Delco types, move the spring end tab out of the retaining
slot and position counterclockwise (Figure 7-17) .
Figure 7-17-Spring End.Tab
CAUTION : DO NOT REMOVE THE SPRING COMPLETELY.
COMPLETE REMOVAL OF THE SPRING
CAN CAUSE THE FAN TO "FREE WHEEL" AND
CAUSE OVERHEATING.
RADIATOR/HEATER AND ENGINE
DEAERATION SYSTEM (After 1983 Model)
Heavy-duty cooling equipment is required when air conditioning
or auxiliary belt-driven equipment is 'installed.
Continuous coolant flow is necessary from the heater connection
on the engine to the heater connection on the
radiator to control oil temperatures during closed thermostat
(warm-up) operation. Shutting off this flow may
result in premature engine or transmission failure.
If a heater unit is not installed in the vehicle or a heater
shut-off valve is required, a line connecting the heater
connection on the engine to the heater connection on the
radiator must be installed . When a shut-off valve is required
in the heating system, it must be "tee'd" into the
system in such a manner as to maintain a continuous flow
between the engine heater connection and the radiator
heater connection at all times.
ENGINE COOLING SYSTEM
7-1 6
NOTE: The heater hose routing should not be altered
from the standard system. If an auxiliary heater
is added, it should be routed similarly to the RPO
(C36) rear heater. Where the heater water return
is routed to the radiator outlet tank, a shut-off
valve should not be placed in the heater circuit .
A nipple has been provided in the radiator outlet tank for
heater return water (Figure 7-18). The temporary rubber
shipping cap should be removed, and the heater return
(suction) hose should be attached to the radiator nipple
using the clamp supplied with the shipping cap.
Figure 7-18 - Radiator Outlet Tank - Heater Return
Water
Figure 7-19-6.2L Diesel Engine Hot Water Flow
SECTION 78
The 454 CID gasoline engine is essentially-the same as
the 6.21- diesel engine shown in Figure 7-19 except that
hot water comes from the thermostat housing. Hot water
enters the bottom of the heater core and exits out the top
for better heat dissipation .
MAINTENANCE AND INSPECTION
The coolant level, appearance and strength should be
checked periodically . It should be drained and replaced
at the intervals recommended in the Maintenance Schedule,
or sooner if it is dirty. Hoses should be checked regularly
for signs of damage or deterioration and hose
clamps tightened if necessary.
Check hoses for cuts or abrasion damage. If the hoses
have become hard and brittle and show signs of cracking
as a result of engine heat, they should be replaced . Hoses
should also be replaced if they are soft and spongy, or
swollen as a result of exposure to oil and grease. Any
flaking or deterioration of the inner lining of the hose is
also reason for replacement. Such particles can clog the
cooling system, reducing its efficiency.
The radiator cap should be washed with clean water and
pressure checked every 12 months.
COOLANT LEVEL
The need for additional coolant can be detected by observing
the level of coolant in the "see through" reservoir
while the engine is at normal operating temperature. The
radiator cap need not normally be removed. (See Figure
7-20.)
Figure 7-20- Coolant Recovery Bottle
ENGINE COOLING SYSTEM
7- 1 7
The coolant level should be at the "Full Cold" mark when
the system is cool or at ambient temperature. After the
vehicle has been driven sufficiently to obtain normal operating
temperatures, the level should be above the "Full
Cold" mark.
Periodically, the radiator cap should be removed to observe
coolant level in the radiator .
CAUTION: TO HELP AVOID THE DANGER OF BEING
BURNED, DO N,PT REMOVE THE RADIATOR CAP
WHILE THE ENGINE AND RADIATOR ARE STILL HOT.
SCALDING FLUID AND STEAM CAN BE BLOWN OUT
UNDER PRESSURE IF THE CAP IS TAKEN OFF TOO
SOON.
Coolant levels in any radiators with coolant recovery bottles
should be maintained to the top of the filler neck.
The recovery bottle should be at its appropriate mark
when checking.
Regardless of whether freezing temperatures are expected
or not, cooling system protection should be maintained
at least to -34°F, to provide adequate corrosion
protection and loss of coolant from boiling . When adding
solution due to a loss of coolant for any reason or in areas
where temperatures lower than -34°F may occur, a sufficient
amount of an ethylene glycol based antifreeze that
meets GM specification 1825-M should be used (GM Part
No. 1052753 - Gallon or equivalent) .
Antifreeze with a glycol content less than required for
-34°F protection, also has a boiling point that is less than
the temperature indicating light setting . The chart shown
in Figure 7-21 shows the boiling point of water and of
glycol in relation to pressure, and as CONCENTRATED
ANTIFREEZE IS FLAMMABLE the chart shown in Figure
7-22 shows the relationship of the freeze point/flash point
of antifreeze at various percentages by volume of solution .
Understanding this potential fire source requires studying
the chart of Figure 7-21 in relation to the information presented
in Figure 7-22. It should be noted that an antifreeze
related fire is the result of sustained driving while the
vehicle is in an "overheat condition" indicated by a full
scale reading of the temperature gage and/or steam from
under the hood. These fires appear after catastrophic engine
damage has occurred.
Figure 7-21 - Boiling Point vs. Pressure Chart-
Water/Glycol
NOTES :
SECTION 713
Factory-installed temperature gages have been calibrated
so the owner sees a mid-range reading as the
"normal" operating temperature. The reason for this is
that many owners tend to perceive 212°F as the boiling
point. However, this is not the case in an engine with
a 15-lb. pressure system and a 50/50 solution of glycol
and water, as shown in Figure 7-21 . If the engine is
equipped with a master gage or with one of the various
digital electronic gages installed by RV manufacturers,
the temperature reading of the engine will be higher
than that of the factory-installed system. No matter
which gage system is utilized, the motor home owner
must realize that the purpose of any gage is to provide
a warning of any rapid change in temperature from the
"normal" reading of that particular gage.
ENGINE COOLING SYSTEM
7-1 8
Figure 7-22 -Coolant Freeze Point/Flash Point
" Alcohol- or methanol-based antifreeze, or plain water,
are not recommended for your engine at any time. They
will not provide proper protection against corrosion .
" Additives in addition to a good quality ethylene glycol
based antifreeze meeting the GM specifications are not
required or recommended. Many of the claims for additives
are associated with better heat transfer or cooling,
but these claims are not supported by test data. In
some instances, the ingredients may be incompatible
with the recommended coolant . Also, when used alone
with water as is sometimes suggested, the additive may
not provide the corrosion protection given by the recommended
coolant solution .
THERMOSTAT CHECK
If the thermostat is suspected of not operating properly,
it can be removed and tested as follows :
1 . Disconnect the battery negative cable at the battery .
2. Drain the cooling system until the radiator coolant level
is below the thermostat.
3. Remove the coolant outlet attaching bolts and remove
the outlet and thermostat.
4. Hang the thermostat on a hook in a minimum of 33%
glycol solution at 25 degrees above the temperature
stamped on the thermostat valve. Submerge the valve
FREEZING POINT & TEMPERATURE
BOILING POINT FREEZE BOIL'`
33% by Volume Solution 0°F 220°F
40% by Volume Solution -12°F 222°F
50% by Volume Solution -34°F 227°F
60% by Volume Solution - 63°F 232°F
68% by Volume Solution -90°F 241°F
(Maximum Freezing
Protection)
Concentrated -8°F 320°F
Flash Point (Cleveland
Open Cup)
68% by Volume Solution None
Concentrated 257°F
Fire Point (Cleveland
Open Cup)
68% by Volume Solution None
Concentrated 266°F
* At sea level atmospheric pressure. The boiling
point decreases about 2 degrees Fahrenheit per
1,000 feet of altitude and increases about 2.5
degrees Fahrenheit per pound of pressure
developed in the system.
BOILING POINT (°F)
PRESSURE
(LBS./SQ. IN.) GLYCOL MIX
WATER (5A/50)
0 212 223.5
1 215.3 227.2
2 218.5 230.0
3 221 .6 233.0
4 224.6 236.0
5 227.4 238.8
6 229.8 241 .6
7 232.8 244.0
8 234.8 246.2
9 237.1 249 .2
10 239.4 251 .7
11 241 .6 254.5
12 243 .7 256.3
13 245 .7 258.3
14 247.8 260.3
15 249.7 262.5
16 251 .7 264.4
17 253.6 266.2
SECTION 7B
completely and agitate the solution thoroughly. Under
this condition, the valve should open .
5. Remove the thermostat and place it in a 33% glycol
solution that is 10 degrees below the temperature indicated
on the valve. With the valve completely submerged
and the solution agitated thoroughly, the valve
should close completely.
If the thermostat tests O.K., it can be reinstalled . If not, it
should be replaced.
Prior to installing the thermostat, make sure the thermostat
housing and coolant outlet sealing surfaces are clean.
1 . Place a 1/8-inch bead of RTV sealer (GM Part No.
1052366 or-equivalent) all around the coolant outlet
sealing surface on the thermostat housing.
2. Place the thermostat in the housing.
3. Install the coolant outlet while the RTV sealant is still
wet. Torque the retaining bolts to 20 ft. lbs.
ENGINE COOLING SYSTEM
Various methods and equipment may be used to perform
this service . If special equipment such as a back flusher
is used, equipment manufacturer's instructions- should be
followed. However, it is advisable to remove the thermostat
before flushing the system .
4. Connect the battery negative cable .
5. Fill the cooling system with an ethylene glycol antifreeze
'and water mixture of 50/50.
6. Start and run the engine with radiator cap removed
until the radiator upper hose becomes hot (thermostat
open) .
7. With the engine idling, add coolant to the radiator until
the level reaches the bottom of the filler neck.
8. Install the cap, making sure arrows line up with the
overflow tube.
FLUSHING COOLING SYSTEM
RADIATOR ADDITIVES
The following information has been extracted from GM
Research Laboratories investigations concerning radiator
additives for the prevention of overheating in the engine
cooling system . The information is provided as an aid to
the motor home owner in understanding the effects of
using radiator additives .
The object of the investigation was to review the use of
radiator additives that are being marketed with the claim
that they improve heat transfer and reduce the coolant
temperature in the engine cooling system.
Conclusions were:
1 . These radiator additives are composed principally of
either water, ethylene glycol, or a combination of the
two, and inhibitors such as those commonly used in
antifreezes . Some additives contain oil and/or a surface
active agent.
2. Tests with these additives fail to show any added benefit
in heat transfer or reduction in coolant temperatures .
3. When these additives are used with water alone, they
will probably provide less corrosion protection than an
antifreeze used at the recommended concentration ;
when used with conventional water-glycol solutions,
the additive inhibitors may not be compatible with those
from the glycol antifreeze.
4. Engine damage may result from loss of coolant due to
overheating if the vehicle owner follows the recommendation
to use these additives with water alone.
(The boiling point of water is below the temperature at
which the warning light is activated and the driver may
not receive warning of a boiling condition .)
5. It is recommended that a strong position be taken
against the use of these additives .
There has been a proliferation of additive products on the
market that are purported to increase the cooling capability
of the cooling system . These products are usually
sold in one-quart containers at a price ranging between
$2.00 and $3.50 .
Although a number of claims are made for these products,
such as added corrosion protection, the removal ofscale,
and pump lubrication, the principal claim is that associated
with improved cooling .
APPENDIX 7.2
The major portion of these additives is either water,
ethylene glycol, or a mixture of the two. Inhibitors have
been added that are typical of those commonly used in
antifreeze or in summer inhibitor additives . Some of the
inhibitors in the additives may be incompatible with inhibitors
in antifreeze solutions ; for example chromates are
often incompatible with ethylene glycol antifreeze. If the
additives are used with water alone, the inhibitors may
not provide sufficient protection to all metals, and in some
cases they may cause excessive corrosion ; for example,
amine inhibitors are aggressive to copper alloys and nitrite
attacks solder unless other inhibitors are present to compensate
for these effects.
The one variant in some cases is the use of a surface
active agent that may increase heat transfer at a metal
surface . One laboratory has shown increased heat transfer
under controlled laboratory conditions but not in automotive
service . However, surface active agents are
often unstable at high temperatures, and they would not
be expected to endure for long . The disadvantage of the
surface active agent, as well as oil, is its tendency to cause
increased foaming in the cooling system.
Most of the claims are associated with better heat transfer
or cooling, but these claims are not supported by testdata.
Since the bulk of the material is water or ethylene glycol,
it should not be expected that the addition of these additives
would prevent overheating or make the engine run
any cooler than when a quart of water or antifreeze had
been added . It is possible that, in practice, the addition of
a quart of this material may restore the coolant to the
proper level, which provides better cooling, but so would
the addition of water or ethylene glycol antifreeze.
The claim that these additives provide better heat transfer
when added to water alone, is apparently based on the
fact that they contain inhibitors that prevent the formation
of corrosion products that would impair heat transfer .
However, the suggestion that they can be used with water
alone may offer a problem . First, the concentration of
inhibitors may be less than that normally provided by a
good antifreeze at the minimum recommended concentration
of 33-1/3 percent and second, the inhibitors may
not be as effective in preventing corrosion as those in a
well-formulated antifreeze. Furthermore, the boiling point
of water is 12 degrees lower than that of a 44 percent
ethylene glycol solution (262°F vs. 250°F at 15 PSIG), and
this may lead to loss of coolant and damage to the engine
because the warning light is set to come on at higher
temperature than that of the boiling point of water.
ENGINE COOLING
INSTRUCTIONS TO RV
MANUFACTURERS
The following information is provided as an aid to the
motor homeowner in understanding the essentials of the
engine cooling requirements as provided to major RV
manufacturers . All chassis manufacturers (Chevrolet/
GMC, John Deere/Ford, Dodge) furnish the various RV
manufacturers with Body Builders Books which provide
basic instructions for the correct building procedures on
an individual chassis.
Essential engine cooling requirements are :
1 . All chassis manufacturers require a minimum grille
opening stated in square inches to provide sufficient
air to cool the manufacturer's engine. The instructions
also indicate the grille to be a minimum of four inches
from the radiator core. Listed below are the minimum
frontal areas for the major manufacturers .
Chevrolet/GMC . . . . . . . . . . . . . . . . . . . . .360 square inches
John Deere/Ford . . . . . . . . . . . . . . . . . . .530 square inches
1976 Dodge. . . . . . . . . . . . . . . . . . . . . . . . . 367 square inches
1979 Dodge . . . . . . . . . . . . . . . . . . . . . . . . . 430 square inches
Dodge and John Deere specify a maximum 45-degree
air entry angle.
2 . Large objects should not be placed in front of the radiator
core or grille such as batteries, spare tires,
washer bottles, coolant overflow tanks, bicycles, etc.,
as these types of items restrict air flow to the radiator
core.
APPENDIX 7-3
3. The grille opening should be "open" in configuration .
Small holes for the grille opening tend to restrict air
flow more than large holes although both may have
the same frontal area.
4. Cooling can be improved by inserting filler panels
between the outer vertical side edges of the
radiator and grille. In addition, a filler panel should
be fitted horizontally from the bottom of the
radiator out to the bottom of the grille . This will prevent
air from by-passing the radiator and exiting
through the front wheel house area or under the
radiator . These panels will force the air through the
radiator .
5. A flexible air-tight seal must be provided between the
upper radiator support and the body to aid idle cooling
and prevent hot air recirculation. The seal assures that
incoming "ram air" must go through the radiator core
rather than by passing the radiator core (going up and
over the core) .
6. Bug screens should be avoided if at all possible. If
conditions require a bug screen, motor home owners
are advised to be alert to possible engine overheating
problems as well as temperature changes . The
screen's mesh should be - at most - half as dense
as that of standard household screening. Household
screening will create an overheating condition . The bug
screen should be removed immediately upon leaving
the bug infested area.
GASOLINE ENGINE
Fuel Types
SECTION 7C ,
Unleaded Gasoline - (In GM Vehicles Designed for
Leaded Fuels) The need for leaded gasoline in the U.S.
is decreasing as older vehicles designed for leaded gasoline
are replaced with new ones requiring unleaded gasoline.
Furthermore, the U.S. Environmental Protection
Agency (EPA) began phasing down the concentration of
lead in leaded gasoline during July, 1985 . These two facts
taken together could result in limited supplies of leaded
gasoline being available for vehicles designed for such
fuel .
The lead phasedown was based on health considerations
and a desire to eliminate fuel-switching - the practice of
using leaded gasoline in vehicles equipped with catalytic
converters. Due to the fact that lead destroys the emission
control properties of catalysts, leaded gasoline should not
be used in engines equipped with these devices. GM supports
this EPA effort to reduce lead emissions and to
reduce fuel-switching .
All GM gasoline-fueled engines in (1 .) passenger cars
starting in 1971, (2.) 1971-78 trucks less than 6,000 lbs.
GVW, and (3.) rucks less than 8,500 lbs. GVW starting
in 1979, were designed to use unleaded gasoline and are
unaffected by lead reduction efforts.
For all GM gasoline-fueled engines in (1 .) pre-1971 passenger
cars and trucks, (2.) 1971-78 trucks over 6,000
lbs. GVW, and (3.) trucks over 8,500 lbs . GVW starting
in 1979, concerns exist about engine knock and exhaust
valve seat durability when such engines are operated on
gasoline without lead .
The octane quality of leaded regular gasoline is generally
higher compared to unleaded regular gasoline . Thus,
switching from leaded regular to unleaded regular in vehicles
designed for leaded regular may cause some engines
to knock. Occasional light knock is of little concern.
However, persistent, heavy knock can cause engine damage
and should be avoided . Two alternatives are available
to avoid knock. The first is to use unleaded premium gasoline
(or a mixture of unleaded regular and unleaded premium).
The other is to retard the engine's basic spark
timing.
The lead in gasoline creates a "cushion" between the
valve and valve seat to minimize wear. Valve seat wear
is aggravated by operating at high engine speeds and
loads, particularly for long periods of time . Engines designed
to use unleaded gasoline have hardened valve
seats to compensate for the removal of lead.
Engines designed to use leaded gasoline can avoid excessive
wear if operation is limited to reasonable speeds
7-22
ENGINE FUELS
ENGINE FUELS
and loads. However, if excessive valve seat wear does
occur, cylinder heads may be rebuilt with hardened valve
seat inserts to avoid recurrence of the problem.
For those engines designed for leaded gasoline, GM recommends
that they continue to be fueled with leaded gasoline
as long as such gasoline is available .
Lead Substitute Additives -GM has not issued a service
bulletin recommending the use of any lead substitute
additive by the individual customer. GM has taken the
position that many additives on the market today do not
have sufficient data and testing to factually back up some
of the claims being made . Some additives may in fact
actually be counterproductive to the government's reasoning
for lead removal and create undesirable emissions
problems as well as being detrimental to overall engine
life . There is a consensus among fuel and lube engineers
that the use of lead substitute additives should not be a
consumer decision and that if the need for an additive
becomes established, the product should be blended into
the gasoline as the fuel is produced by the the gasoline
supplier to ensure better chemistry control .
Gasohol - Gasohol, a mixture of 10 percent ethanol
(grain alcohol) and 90 percent gasoline may be used in
Chevrolet gasoline engines without voiding the warranty .
However, because of the composition of gasohol, engines
will tend to operate leaner with gasohol than with gasoline.
This can result in drivability conditions usually associated
with leaner mixtures. Also the increased volatility of
gasohol can contribute to hot weather drivability problems
if adjustments are not made to the gasoline blend during
the refining process.
The higher octane rating of gasohol compared to most
unleaded gasolines, could help" reduce the tendency for
spark knock. But, gasohol contains less energy than gasoline,
and fuel economy may or may not be quite as good.
However, in some instances, depending on the entire design
and calibrations, and certain operating conditions, it
is possible to get improved fuel economy.
Exhaust emission levels may change up or down with the
use of gasohol, again, depending on the calibration of the
engine . At the present time, however, the EPA has not
restricted the use of gasohol .
If gasohol is spilled on a painted surface, some dulling or
softening of the paint may result.
NOTE: Refer to the information contained in Appendix
7-4 and Appendix 7-5 at the end of this section
of the manual concerning the use of gasohol in
vehicles equipped with gasoline engines, and potential
problems of using methanol/gasoline
blends.
DIESEL ENGINE
Fuel Types
NOTE : Do not use starting fluids . Such aids can cause
immediate engine damage.
Diesel fuel is available in No. 1 or No. 2 grades. The
difference between the grades is that No. 1 diesel fuel
has had much of the paraffin (wax) removed. While the
wax content increases the amount of energy in the fuel,
it can clog the fuel filter(s) in cold weather, and stop the
flow of fuel to the engine.
The Cetane Number used in rating diesel fuels is an indication
of the energy content of the fuel - the higher the
Cetane Number, the higher the energy content . The
higher Cetane rating will improve the cold-starting performance
of the engine, as long as the higher wax content
SECTION 7C-ENGINE FUELS
does not impede the flow of fuel through the system. This
introduces two other factors which affect diesel fuel -
Cloud Point and Pour Point. The Cloud Point represents
the temperature at which a predetermined percentage of
the wax content in the fuel solidifies. The Pour Point represents
a lower temperature at which the fuel cannot be
made to flow.
The moisture content of the fuel can also affect cold
weather starting and performance. Water can separate
out of the fuel, settling in low points of the fuel line and
freezing, or forming minute ice particles which flow into
the filter(s) and tend to clog the filter(s) .
Additives can be used to lower the Pour Point of the fuel,
and to prevent moisture freezing in the fuel. However$
additives will have little effect on the Cloud Point. Mixing
different grades of diesel fuel can also be used to change
the Pour Point and to change the Cloud Point as well.
USE OF GASOHOL IN GASOLINE
ENGINES
The following information was extracted from a Chevrolet
Dealer Service Information Bulletin relating to the use of
gasohol in vehicles equipped with gasoline engines.
Reference: Chevrolet Dealer Service Information Bulletin
No. 80-1-3 (July, 1979)
Gasohol, a fuel generally composed of 10 percent ethanol
(grain alcohol) and 90 percent gasoline, is receiving considerable
attention as a fuel for gasoline engines. It is
possible that other kinds of alcohol, such as methanol
(wood alcohol) may be added to gasoline in the future ;
however, this bulletin deals only with gasohol containing
up to 10 percent ethanol . (Gasohol containing methanol
is not being marketed at this time.) The purpose of this
bulletin is to provide information which may be helpful in
answering questions about gasohol which may arise
regarding:
" Availability
" Drivability
" Fuel Economy
" Service Adjustments
" Warranty Coverage
" Emission Levels
Availability
Gasohol currently is available at many retail stations in
the Midwest and some retail stations on the East Coast.
Nationwide availability is expected to increase .
Drivability
Due to the composition of gasohol, vehicles equipped with
gasoline engines will operate leaner with gasohol than
with gasoline . This leaner operation with gasohol may
tend to cause drivability conditions usually associated with
leaner mixtures . However, drivability of vehicles with Computer
Controlled Catalytic Converter (C-4) or Closed Loop
Catalytic Converter (CLCC) Systems probably will be affected
less, because these systems compensate for the
leaning effect of gasohol.
NOTE: (Provided as a reference for the motor home
owner.) If your vehicle is several years old, you
should plan on changing all of the fuel filters at
least once and the carburetor filter more than
once. The reason given for this is that alcohol in
itself is a solvent which dissolves the deposits left
by gasoline in the fuel system .
APPENDIX 7.4
The increased volatility of gasohol also can contribute to
hot-weather drivability problems if, during the refining
process, adjustments are not made to the gasoline blend.
In general, gasohol has a higher octane rating than most
unleaded gasolines, and it could help reduce the tendency
for spark knock.
Fuel Economy
Gasohol (10 percent ethanol, 90 percent gasoline) contains
less energy than gasoline by itself . Consequently,
fuel economy of gasohol may not be quite as good as
gasoline. However, there are differences in engine design
and calibration which make it possible in some instances
to achieve better fuel economy with gasohol.
Service Adjustments
Specified engine settings must not be changed for
gasohol use. The service specifications for which the vehicle
has been certified must be maintained.
Warranty Coverage
The use of gasohol containing up to 10 percent ethanol
will not void the vehicle warranty. Dealers are requested
to inform their Area Service Manager of any fuel system
failures which are believed to be related to gasohol use .
If gasohol contacts a painted surface, it may cause dulling
or softening of the paint. Dulling or softening of paint due
to contact with gasohol is not covered under the vehicle
warranty.
Any drivability condition which is related solely to gasohol
use is not covered under the vehicle warranty.
Emission Levels
Some changes in vehicle exhaust emission levels may
occur when using gasohol. For example, carbon monoxide
(CO) emissions will decrease in most vehicles, due
to leaner mixture, but hydrocarbons (HC) and oxides of
nitrogen (NOx) emissions may either decrease or increase,
depending on how the engine is calibrated. Exhaust
emission levels of vehicles equipped with C-4 or
CLCC systems should be affected less than vehicles without
these systems . The generally higher volatility of gasohol
compared to gasoline may result in increased
evaporative emissions .
At the present time, the Environmental Protection Agency
is not restricting the use of gasohol. However, local or
state regulations, if applicable, must be observed .
The following information has been extracted from a GMC
Newsletter and is provided as an aid to the motor home
owner concerning the potential problems posed by methanol/
gasoline blends.
Reference : GMC Truck & Bus Group Newsletter
(January, 1984)
USE OF GASOLINE/ALCOHOL
BLENDS EXPLAINED IN
OWNER'S MANUALS
Owners of 1984 model GM automobiles are given
specific information in their owner's manuals on
what types of fuel may be used in their vehicles . On
the subject of gasoline/alcohol blends, the manuals
state :
Gasoline/Ethanol Blends
Blends of unleaded gasoline and ethanol (grain alcohol),
sometimes known as gasohol, are available
in some areas. You may use these blends in your
car, if they are not more than 10 percent ethanol,
without jeopardizing the New Vehicle and Emission
Warranties. Be sure the gasoline/ethanol blend has
octane ratings no lower than those recommended
for unleaded gasoline . Most drivers will not notice
operating differences with blends of up to 10 percent
ethanol, but some may. In that case, your dealer
can make certain adjustments, provided they do not
violate the Federal Emissions Standards . If you are
still not satisfied with ethanol-gasoline blend performance,
you may prefer to use unleaded gasoline .
Other Gasoline/Alcohol Blends
Some fuel suppliers sell gasoline containing alcohol
without advertising the presence of alcohol or giving
it a special name such as gasohol . If you are not
sure whether there is alcohol in the gasoline you
buy, check with the service station operator .
DO NOT USE gasolines containing methanol
(methyl or wood alcohol) that do not also contain
cosolvents and corrosion inhibitors for methanol.
Also, DO NOT USE gasolines that contain more
than five percent methanol even if they contain cosolvents
and corrosion inhibitors. Fuel system damage
or vehicle performance problems resulting from
the use of such fuels are not the responsibility of
General Motors and may not be covered under the
new vehicle warranties.
Although gasolines containing five percent or less
methanol and appropriate cosolvents and inhibitors
for methanol may be suitable for use in your car,
evidence of their suitability is as yet incomplete ;
therefore GM cannot, at this time, endorse their use.
APPENDIX 7-5
METHANOL/GAPOSE SOLINE BLENDS
POTENTIAL PROBLEMS
7-25
METHANOL/GASOLINE BLENDS
POSE POTENTIAL PROBLEMS
Gasoline quality is an important factor in providing satisfactory
engine and vehicle performance and fuel system
life. Gasoline has traditionally been composed entirely of
a mixture of hydrocarbons and its quality generally has
been sufficient to prevent problems with vehicle performance
and fuel system materials .
In recent years, howevet, the quality of some gasolines
has changed. Economic and other factors have led suppliers
to use alcohols as gasoline components. The first
of these was ethanol (grain alcohol), which was popularized
in gasoline under the name "Gasohol." Vehicle performance
and fuel system durability with gasolines
containing up to 10 percent ethanol, by volume, have
generally been satisfactory .
More recently, methanol (wood alcohol), an alcohol with
distinctly different properties than ethanol, has become a
gasoline blending agent. The,addition of methanol to gasoline
for use in motor vehicles is receiving increased attention
due to favorable economics, excess methanol
production capacity, and the desire to reduce petroleum
imports .
General Motors recognizes the favorable aspects of pure
methanol as a future alternative fuel and certainly will
produce cars that can use methanol if it becomes generally
available . However, current use of methanol in gasoline
can pose problems if used in today's cars over an
extended period - even at low methanol concentrations
in gasoline .
GM is concerned about the rapid increase in the use of
methanol/gasoline blends in today's cars for two reasons :
" There is no hard evidence on how much methanol can
be blended with gasoline without adversely affecting
vehicle operation and durability.
" There is no adequate service station pump labeling
system that will tell motorists the methanol content of
the fuel they are purchasing.
There is limited information that suggests small amounts
(up to five percent) of methanol in gasoline may be suitable
if a cosolvent- an ingredient that prevents the gasoline
and methanol from separating when trace amounts
of water are in the fuel - and a corrosion inhibitor to
prevent damage to fuel system components are used.
Evidence on the suitability of such blended fuels is incomplete
and, therefore, their use cannot be endorsed by
GM at this time.
METHANOL/GAS'LOLINE
BLENDS POSE POTENTIAL
PROBLEMS (Cont1d)
It is likely some engines and fuel systems will be sensitive
to methanol/gasoline blends that contain higher concentrations
(greater than 10 percent) of methanol - even if
the fuels contain cosolvents and corrosion inhibitors. This
sensitivity is generally related to compatibility with materials
commonly used in vehicle fuel systems, such as fuel
tank plating and certain rubber parts in carburetion systems.
Also, drivability - performance of the vehicle - is
adversely affected .
GM is continuing to evaluate methanol/gasoline blends in
both laboratory and vehicle tests to determine the effects
of the blends on fuel system materials, engine deposits,
drivability, emissions and fuel economy.
There are economic advantages that encourage blending
methanol with gasoline. The average national tank price
for unleaded gasoline sold to service station dealers (excluding
taxes) in August, 1984 was approximately 94
cents a gallon, while methanol's cost was between 45 and
49 cents a gallon . On the other hand, ethanol's cost was
between $1 .62 and $1 .80 per gallon . Ethanol/gasoline
blends are competitive with gasoline only if a tax subsidy
is allowed, but methanol/gasoline blends are not only
competitive, they are enticing for the refiner, blender and
retailer.
The U.S. Environmental Protection Agency (EPA) has
granted waivers, legally allowing the blending of methanol
in gasoline . Waivers cover methanol concentrations as
high as 12 percent, as long as cosolvents are used . GM
and other auto companies have not agreed with the EPA's
decisions granting waivers for methanol/gasoline blends.
The concern over use of methanol/gasoline blends has
been heightened because illegally high levels of methanol
have been found in some gasolines.
An EPA probe that began in the spring of 1983 in the
Detroit area, revealed illegally high levels of methanol in
gasoline . Out of 250 samples of unleaded gasoline from
about 150 service stations, about eight percent - or 20
samples - had levels of methanol above those allowed
by waivers, or did not contain cosolvents.
Because of concern over the compatibility of methanol/
gasoline blends with current vehicle engines and fuel systems,
and illegal blending of methanol in gasoline, a number
of states are planning to require that the methanol
content of the fuel be posted on dispensing pumps. Although
this is a step in the right direction, GM believes
that motorists would be better served by a uniform labeling
system nationwide. This would eliminate confusion
caused by states adopting different labels .
APPENDIX 7-5
7-26
Historical Perspective
Alcohol/gasoline mixtures have been studied for more
than 50 years. In the 1960s and early 1970s, the use of
these blends was proposed (not always appropriately) as
a way to reduce vehicle exhaust emissions and improve
fuel economy. However, because the cost of alcohol was
significantly higher than that of gasoline, the widespread
use of alcohol/gasoline blends was not economically
feasible.
Two significant actions of the past decade have renewed
and expanded interest in alcohol/gasoline blends.
First, the severe interruptions of petroleum imports emphasized
the need to increase production of domestic
energy sources and reduce dependence on imported oil.
The production of alcohol fuels, particularly ethanol, became
politically attractive in the late 70s at the height of
the energy crisis . Its use was encouraged through tax
subsidies. Commonly sold as Gasohol, it is now also marketed
as unleaded, super unleaded, or premium unleaded
gasoline (depending on its octane level), marked "with
ethanol ."
Also, during the recent recession, capacity for production
of methanol from natural gas far exceeded demand. Methanol
thus assumed a new attraction as a gasoline blending
agent. The outlook for use of pure methanol as an automotive
fuel is positive because the technical knowledge
necessary to design and build methanol-fueled engines
and vehicles is rapidly developing . (See Figure A7-5-1 .)
In blends with gasoline, as stated earlier, methanol may
not be suitable for use in either existing vehicles or future
model year vehicles unless the vehicles are modified .
NOTE: Several trade publications have predicted a sharp
increase in the amount of methanol used as automotive
fuel by the end of the decade. The
"Lundberg Letter" projects methanol fuel use in
1990 will be 40 times greater than in 1980.
The second action which increased interest in alcohols
as fuels was the reduction in the amount of lead antiknock
additives used in gasoline . This reduction spurred by the
EPA, occurred for two reasons:
" The need for unleaded gasoline in cars equipped with
catalytic converters.
" The need to limit the emissions of lead into the atmosphere
(by lowering permissible lead concentrations in
leaded fuel).
Figure A7-5-1- U.S. Fuel Methanol Forecast
Alcohols offer a means of replacing some of the octane
(antiknock) quality previously provided by lead
compounds .
Major Disadvantages- of Methanol/Gasoline
Blends
There are a number of disadvantages associated with the
use of methanol/gasoline blends in vehicles designed for
gasoline. Of major significance are:
" DETERIORATION OF FUEL SYSTEM MATERIALS.
Rubber, plastic, and metallic fuel system components
in most vehicles were designed for use with gasoline,
and may not provide satisfactory service with methanol/
gasoline blends. Although few long-term durability tests
have been run with blends, the results from a number
of laboratory evaluations, as well as problems reported
by motorists, make it clear that a variety of problems
can occur. Most material problems are a function of
time rather than distance traveled, so a 50,000-mile test
completed in one year may not indicate what would
happen during 50,000 miles of operation over four or
five years. Components possibly affected include fuel
tanks, in-tank fuel pumps, carburetion and fuel injection
systems, and nitrile rubber commonly used in vehicle
fuel systems.
APPENDIX 7-5
METHANOL/GASOLINE
BLENDS POSE POTENTIAL
PROBLEMS (Cont'd)
7-27
" DRIVABILITY. Drivability is generally worse with
methanol/gasoline blends than with gasoline alone . In
hot weather, the generally high volatility of the blends,
compared with gasoline, causes a greater tendency
toward vapor lock problems. Cold weather problems -
stalling and hesitation - have been reported.
" SEPARATION . The presence of even trace amounts
of water in the fuel system may cause methanol/gasoline
blends to become cloudy and separate into two
layers, a gasoline layer on top and an alcohol/water
layer on the bottom. A vehicle will not run satisfactorily
on the alcohol/water mixture and corrosion of fuel system
parts and deterioration of rubber parts can be
greatly accelerated by contact with this mixture . Water
tolerance of blends is increased by cosolvents, but even
these do not completely eliminate the separation
problem.
" FUEL ECONOMY. In late-model cars, fuel economy
(miles per gallon) generally decreases with the addition
of methanol to gasoline. This is due to the lower energy
content (per gallon) of methanol compared with gasoline.
For example, a blend of 10 percent methanol in
gasoline contains about five percent less energy per
gallon than gasoline .
" EVAPORATIVE EMISSIONS. Unless major changes
are made in the distillation characteristics of gasoline,
the addition of methanol to it significantly increases vapor
pressure. This almost always results in a substantial
increase in vehicle evaporative emissions .
Regulatory Considerations
The regulatory aspects of methanol/gasoline blends are
complex . The Clean Air Act prohibits the addition of additives
to unleaded fuel, including methanol, unless the
fuel additive manufacturer obtains a waiver from the EPA.
In order to obtain such a waiver, the fuel additive manufacturer
must show that the fuel will not cause - or contribute
to - the failure of the vehicle or engine to meet
the applicable emission standards for five years, or 50,000
miles.
The EPA has published guidelines that stress the need
for development of data on possible methanol blending
problems . GM supports the principles embodied in the
guidelines, but believes it is important that the EPA give
careful consideration to potential problems when reviewing
any fuel additive waiver application for alcohol/
gasoline blends. During the last five years, a number of
waivers have been granted.
METHANOUGASOLINE
BLENDS POSE POTENTIAL
PROBLEMS (Cont'd)
GM and other automobile manufacturers are concerned
that some of the blends approved by the EPA may be
detrimental to vehicle emissions, performance and components.
Although several fuel suppliers have been
successful in marketing methanol/gasoline blends, the
long-term effects of the blends on vehicle durability are
not yet known. To assure customer satisfaction with its
vehicles, GM is establishing a system to track reported
APPENDIX 7-5
vehicle problems to determine if methanol/gasoline blends
are responsible . If further investigation determines
methanol/gasoline blends can be used in the existing fleet
of vehicles without materials, drivability, or emissions
problems, GM believes their use should be permitted. But
only with adequate labeling of fuel at the pump will consumers
be able to recognize the contents in the fuel they
are purchasing .
ENGINE FUEL SYSTEMS
There are distinct differences between the gasoline and
diesel engine fuel systems. The 5.7L and 7.4L (Mark IV)
gasoline engines use a carburetor to mix fuel with air.
Strong engine vacuum, drawing intake air through the
carburetor venturis, causes fuel to flow from the carburetor
ports to be mixed in the air stream turbulence. This air/
fuel mixture is distributed to each cylinder through the
intake manifold. Engine speed is controlled by the position
of throttle plates in the carburetor which open and close
(by means of the accelerator linkage) to vary the amount
of air/fuel mixture entering the manifold and cylinders .
In the diesel engine, fuel is injected directly into a prechamber
above each cylinder where it is mixed with air .
Engine speed is controlled by varying the amount of fuel
injected.
The components used in each system, gasoline and diesel,
will be described in separate sections .
GASOLINE ENGINE
SYSTEM DESCRIPTION
SECTION 7D - ENGINE FUEL SYSTEMS
The gasoline engine fuel system includes the fuel tank,
fuel pump, fuel filter, carburetor and all fuel and vacuum
lines.
FUEL TANK
The fuel tank is located behind the rear axle and is
strapped to the frame. It includes the fuel filler cap and
Figure 7-23-Evaporative Control System
7-29
neck, and a fuel gage sending unit. Its sole purpose is to
provide a place for fuel storage.
FUEL PUMP
The fuel pump is located on the lower front half of the
engine block on the passenger's side. Its purpose is to
provide adequate pressure to move fuel to the carburetor.
The fuel pump is a diaphragm-type pump and is actuated
by the rocker arm through a link and a push rod .
Some vehicles have a fuel pump with an outlet for a
vapor return system. Any vapor which forms, is returned
to the fuel tank along with hot fuel through a separate
line. This greatly reduces any possibility of vapor lock
by keeping cool fuel from the tank constantly circulating
through the fuel pump. Some units are built
with both mechanical and electric in tank pumps.
EVAPORATIVE CONTROL SYSTEM
Light-duty and some heavy-duty vehicles are equipped
with an emissions system designed to prevent escape of
fuel vapor to the atmosphere (Figure 7-23). Vapor generated
by evaporation of fuel in the tank, previously exhausted
to the atmosphere, is transferred by an emission
line to .the engine compartment . During periods of inoperation,
an activated. charcoal canister located in the
emission line stores any vapor generated, for consumption
during the next period of operation .
L
VENT TO ATMOSPHERE
(Above 10,000 Lbs. GVW - Federal)
Z
-
---
r _J LT I'II
I I
L__J
CHARCOAL_
CANISTER
(Below 10,000 Lbs.
GVW - Federal;
All GVW - California)
TRANSFER VALVE
(If So Equipped)
AUXILIARY FEL TANK MAIN FUEL TANK (If-so equipped- ,-requires- additional
charcoal canister with NOTE: 1985-1/2 thru 1989 HD5 Emissions - All capacity for second tankv.
ent)ing models are vented to charcoal canister.
SECTION 7D
The amount of vapor drawn into the engine at any time
is too small to have any effect on fuel economy or engine
operation.
With this closed system, it is extremely important that only
vapors be transferred to the engine. To avoid the possibility
of liquid fuel being drawn into the system, the following
features are included as part of the total system :
1 . A fuel tank overfill protector is provided on all series
to assure adequate room for expansion of liquid fuel
volume with temperature changes. (Fill is limited to 80-
90 percent total capacity.)
2. A one-point fuel tank venting system is provided on all
series to assure that the tank will be vented under any
conceivable vehicle attitude.
3. To protect the tank from mechanical damage in the
event of excessive internal or external pressures resulting
from the operation ofthis closed system, a pressure-
vacuum relief valve, located in the gas cap, will
control the tank's internal pressure.
System Hook-Up for Auxiliary Tank
If an auxiliary fuel tank is to be added, it must be vented
as shown in Figure 7-23. See Figure 7-24 for additional
fuel tank considerations .
FUEL FILTERS
An engine fuel filter is located in the carburetor fuel inlet.
These fuel filter elements are of pleated paper. Elements
ENGINE FUEL SYSTEMS
are placed in the inlet hole with the gasket surface outward.
A spring holds the element outward, sealing it by
compressing a gasket surface against the inlet fitting .
The carburetor inlet fuel filter should be replaced at the
internals shown in the Maintenance Schedule. A plugged
filter and/or check valve will restrict fuel flow.
After assembling any filter element in the carburetor, always
start the engine and check for leaks in the fuel line
and fittings before installing the air cleaner ..
For the P-Series, an additional fuel filter is located in the
fuel line along the inside or outside of the right frame rail
depending on the year built. It is replaced by disconnecting
the fuel line on both sides of the filter assembly, removing
the old assembly, installing a new one, and then reconnecting
the fuel line. Use caution to avoid fuel spillage .
NOTE: The position of the filter(s) may vary on the
P-Series with the installation of aftermarket fuel
tanks. The installation of additional filters at each
tank is not recommended, because of the added
work load these restrictions would place on the
mechanical fuel pump.
A woven plastic filter is located on the lower end of the
fuel pickup pipe in the fuel tank. This filter prevents dirt
from entering the fuel line. Normally, no maintenance is
required. Fuel stoppage at this point, indicates that the
tank contains an abnormal amount of sediment; consequently,
the tank should be removed and cleaned
thoroughly.
RETURN LINE
IMPORTANT STORAGE
VAPOR DOME ALLOWS NECESSARY
ROOM FOR FUEL EXPANSION.
POSITION OF SPIT BACK
TUBE IN CONJUNCTION WITH
LENGTH/POSITION OF FUEL FILL
NECK CONTROLS FUEL FILL
LEVEL TO APPROX. 80%
RESTRICTED VENT
.050
ORIFICE
ELECTRICAL
CONNECTION
FOR FUEL GAGE
TYPICAL GM FUEL TANK
TYPICAL SQUARE WELDED-UP---'O
RV TANK SHOULD INCLUDE
SAME FEATURES AS GM TANK
ASPECIAL CAP DRAWS IN AT 2.0-2.4 INCHES
OF VACUUM = 27-32 INCHES OF WATER
COLUMN. THE CAP BLOWS OFF AT 2.2-2 .9
PSI = 60-80 INCHES OF WATER COLUMN.
SUCTION PICK-UP
W/SOME FORM OF SOCK FILTER
FOR ROCKS AND BROOMSTRAWS
AUX. POWER SHOULD
NOTGO TO BOTTOM OF TANK
TO ALLOW ENGINE RESTART TO
GETOFF CAMP GROUND
ALL SHOULD HAVE RESTRICTED
VENT TO PREVENT FUEL SIPHON
WITH FUEL SLOSH AND
DETER OVERFILL
.055 DEPTH OF
060 RESTRICTOR SPIT BACK TUBE CUrv i rsvw 80% TO 90% FILL
Figure 7-24-Typical Fuel Tank Design Considerations
7-30
CARBURETOR
The carburetor is located on the top of the engine block,
just under the air filter housing . Proper operation of the
carburetor is extremely important as it performs several
necessary functions . First, it controls the amount of air
drawn in by the engine and controls the amount of fuel
that is combined with air to form a combustible mixture .
This must be done adequately to cover a wide range of
operating speeds and conditions. Consequently the carburetor
also controls engine output and speed by varying
the amount of mixture reaching the eight cylinders .
Finally, the carburetor provides vacuum control for the
spark advance and vacuum source for many of the federally
mandated emission controls .
The M4MC model carburetor is used on most of the gas-
TBI
INJECTOR TBI UNIT THROTTLE BODY
PRESSURE REGULATOR
IN-LINE
FUELFILTER FUEL PRESSURE LINE
FUEL RETURN LINE
PURPOSE
SECTION 7D
GENERAL DESCRIPTION
The fuel control system is controlled by an electronic
control module. The ECM is the control center of the
computer command control system and is located
under the steering column support bracket.
The basic function of the fuel control system is to control
fuel delivery to the engine. Fuel is delivered to the
engine by a throttle body injection (TBI) unit.
The main control sensor is the oxygen (O~ sensor,
which is located in the exhaust pipe. The OZ sensor
tells the ECM the amount of oxygen in the exhaust
gas, and the ECM changes the air/fuel ratio to the
engine by controlling the fuel injector. A 14.7:1 air/fuel
ratio is required for efficient catalytic converter operation.
Because the constant measuring and adjusting
of the air/fuel ratio, the fuel injection system is called a
"Closed Loop" system (Figure 7-26).
ENGINE FUEL SYSTEMS
Figure 7-25 - TBI Fuel Supply System (Typical)
7-31
oline engines. It features tamper-resistant controls to discourage
readjustment of factory settings, which could
affect either or both emission control and drivability .
MAINTENANCE AND INSPECTION
The system should be inspected and maintained in accordance
with the Maintenance Schedule. Fuel lines
should be checked for signs of leakage, damage or deterioration.
Clamps must be tightened if they are loose.
Filters in the fuel line and the evaporative control system
should be replaced at the recommended intervals. The
carburetor choke linkage should be checked and the
mounting bolts tightened as recommended.
CAUTION
1990 fuel injection requires only no lead fuel be used
as regular fuel will ruin the catalytic converter.
MODES OF OPERATION
The ECM monitors voltages from several sensors to
determine how much fuel to give the engine. The fuel
is delivered under one of several conditions called
;.`modes." All the modes are controlled by the ECM .
Starting Mode
When the key is first turned "ON," the ECM turns on
the fuel pump relay for two seconds and the fuel pump
builds up pressure to the TBI unit. The ECM checks the
coolant temperature sensor, throttle position sensor
(TPS), manifold absolute pressure map sensor, and
crank signal, then determines the proper air/fuel ratio
for starting . This ranges from 1 .5:1 at -36°C (-33°F) to
14.7:1, at 94°C (201°F) running temperature .
The ECM controls the amount of fuel delivered in the
starting mode by changing how long the injector is
turned "ON" and "OFF." This is done by "pulsing" the
injector for very short times.
OTHER
SENSOR ELECTRONIC 14 .7 .1 COMMAND
INPUT CONTROL "CLOSED LOOP"
INFORMATION MODULE 6S 2692-6E
Figure 7-26 - "Closed Loop" TBI System
Clear Flood Mode
If the engine floods, clear it by pushing the accelerator
pedal down all the way. The ECM then pulses the injector
at a 20:1 air/fuel ratio, and holds this injector
rate as long as the throttle stays wide open, and the
engine is below 600 rpm. If the throttle position
becomes less than 80%, the ECM returns to the Starting
mode.
Run Mode
The Run mode has two conditions called "Open Loop"
and "Closed Loop."
Open Loop
SECTION 7D-ENGINE FUEL SYSTEMS
When the engine is first started, and it is above 400
rpm, the system goes into "Open Loop" operation. In
"Open Loop," the ECM ignores the signal from the 02
sensor, and calculates the air/fuel ratio based on inputs
from the coolant temperature and MAP sensors.
The system stays in "Open Loop" until the following
conditions are met:
1 . The 02 sensor has varying voltage output, showing
that it is hot enough to operate properly. (This
depends on temperature.)
2. The coolant temperature sensor is above a
specified temperature.
3. A specific amount of time has elapsed after starting
the engine .
The 7.4L engine is designed to operate "Open Loop" at
idle. The system will go to "Closed Loop" when the
rpm is increased and all conditions above are met.
Closed Loop
The specific values for the above conditions vary with
7-32
different engines, and are stored in the programmable
read only memory (PROM). When these conditions are
met, the systems go into "Closed Loop" operation. In
"Closed Loop," the ECM calculates the air/fuel ratio
(injector on-time) based on the signal from the 02 sensor.
This allows the air/fuel ratio to stay very close to
14.7:1 .
Acceleration Mode
The ECM looks at rapid changes in throttle position
and manifold pressure, and provides extra fuel .
Deceleration Mode
When deceleration occurs, the fuel remaining in the intake
manifold' can cause excessive emissions and
backfiring . Again, the ECM looks at changes in throttle
position and manifold pressure and reduces the
amount of fuel. When deceleration is very fast, the
ECM can cut off fuel completely for short periods.
Battery Voltage Correction Mode
When battery voltage is low, the ECM can compensate
for a weak spark delivered by the distributor by:
" Increasing injector on time of fuel delivered
" Increasing the idle rpm
" Increasing ignition dwell time
Fuel Cutoff Mode
No fuel is delivered by the injectors when the ignition
is "OFF." This prevents dieseling . Also, fuel is not
delivered if no reference pulses are seen from the
distributor, which means the engine is not running.
Fuel cutoff also occurs at high engine rpm, to protect
internal engine components from damage.
FUEL CONTROL
OPERATION
The fuel control system (Figure 7-27) consists of the
following components:
" Throttle body injection (TBI) unit
" Fuel pump
" Fuel pump relay
" Fuel tank
" Accelerator control
" Fuel lines
" Fuel filters
" Evaporative emission control system
The fuel control system has an electric fuel pump,
located in the fuel tank on the gage sending unit. It
pumps fuel to the throttle body through the fuel supply
line, then through an in-line fuel filter . The pump is
designed to provide pressurized fuel at about 125
kPa (18 psi).
SECTION 7D
a FUEL PUMP AND
SENDING UNIT
FUEL SUPPLY LINE
FUEL FILTER
TBI UNIT
FUEL RETURN LINE 4S0055-6E
Figure 7-27 - Fuel Control System
A pressure regulator in the TBI keeps fuel available to
the injectors at a constant pressure between 62 and 90
kPa (9 and 13 psi). Fuel in excess of injector needs is
returned to the fuel tank by a separate line.
The ECM controls the injectors that are located in the
fuel meter body assembly of the TBI. The injectors
deliver fuel in one of several modes, described above .
In order to properly control the fuel supply, the fuel
pump is operated by the ECM through the fuel pump
relay and oil pressure switch (see "Fuel Pump Electrical
Circuit").
MODEL 220 TBI UNIT
Model 220, (Figure 7-28), consists of three major casting
assemblies:
" Fuel meter cover with:
- Pressure regulator
13
a5 6
FUELINJECTORS
THROTTLE BODY ASSEMBLY
THROTTLE POSITION SENSOR (TPS)
IDLE AIR. CONTROL (IAC) VALVE ASSEMBLY
FUEL METER BODY ASSEMBLY
FUEL METER COVER ASSEMBLY 8P 0922-AS
Figure 7-28 - Model 220 TBI Unit
ENGINE FUEL SYSTEMS
7-33
" Fuel meter body with:
- Fuel injectors
" Throttle body with:
- Idle air control (IAC) valve
- Throttle position sensor (TPS)
Vacuum Ports
The throttle body portion of both TBI units maycontain
ports located above, or below the throttle valve. These
ports generate the vacuum signals for the exhaust gas
recirculation (EGR) valve, MAP sensor, and the
canister purger purge system .
Fuel Injector(s)
The fuel injectors (Figure 7-29) are solenoid-operated
device, controlled by the ECM. The ECM turns on the
solenoid, which lifts a normally closed ball valve off a
seat. Fuel, under pressure, is injected in a conical
spray pattern at the walls of the throttle body bore
above the throttle valve.
The fuel which is not used by the injectors passes
through the pressure regulator before being returned
to the fuel tank.
Pressure Regulator
The pressure regulator(see Figure 7-29) is a diaphragma
13
PRESSURE REGULATOR
®FUEL INJECTOR
FUEL INJECTOR INLET FILTER
THROTTLE BODY ASSEMBLY
FUEL FROM PUMP
INJECTOR ELECTRICAL TERMINALS
CONSTANT BLEED - (SOME MODELS)
PRESSURE REGULATOR DIAPHRAGM ASSEMBLY
PRESSURE REGULATOR SPRING
FUEL RETURN TO TANK
THROTTLE VALVE
0G
8P0320-SY
Figure 7-29 - TBI 220 Unit Operation
operated relief valve with injector pressure on one side
and air cleaner pressure on the other. The function of
the regulator is to maintain a constant pressure at the
injectors at all times, by controlling the flow in the
return line (by means of a calibrated bypass).
The pressure regulator on a TBI 220 unit is serviced as
part of the fuel meter cover and should not be
disassembled.
Idle Air Control System
SECTION 7D
All engine idle speeds are controlled by the ECM
through the idle air control (IAC) valve mounted on the
throttle body (Figure 7-30). The ECM sends voltage
pulses to the IAC motor windings causing the IAC
motor shaft and pintle to move "IN" or "OUT" a given
distance (number of steps) for each pulse, (called
counts).
0
A
B
D
FUEL METER COVER & BODY ASSEMBLIES
THROTTLE BODY ASSEMBLY
IDLE AIR CONTROL VALVE ASSEMBLY
FILTERED AIR INLET
PINTLE
THROTTLE VALVE
VACUUM PORTS - FOR ENGINE OR EMISSION
CONTROLS 8P 0319-SY
Figure 7-30 - Idle Air Control System (TBI 220 Unit)
This movement controls airflow around the throttle
plate, which in turn, controls engine idle speed, either
cold or hot. IAC valve pintle position counts can be
seen using a "Scan" tool. O counts corresponds to fully
closed passage, while 140 counts or more (depending
on the application) corresponds to full flow.
" Actual or "controlled" idle speed is obtained by the
ECM positioning the IAC valve pintle . Resulting idle
speed is generated from the total idle air flow (IAC/
ENGINE FUEL SYSTEMS
7-34
passage + PCV + throttle valve + vacuum leaks) .
Controlled idle speed is always specified for normal
operating conditions. Normal operating condition is
coolant temperature in operating range, the A/C is
"OFF," automatic transmission in drive with proper
Park/Neutral switch adjustment. A high or low
coolant temperature, or A/C clutch engaged may
signal the ECM to change the IAC counts.
The minimum idle air rate inset at the factory with a
stop screw. This setting allows enough air flow by
the throttle valves to cause the IAC valve pintle to be
positioned a calibrated number of steps (counts)
from the seat during normal controlled idle operation.
The IAC counts will be higher than normal on
an engine with less than 500 miles, or an engine
operating at high altitude or an engine with an accessory
load such as the alternator, A/C, power
steering or hydra-boost brakes activated.
0
11
TERMINAL PINS
BALL BEARING ASSEMBLY
STATOR ASSEMBLY
ROTOR ASSEMBLY
SPRING .
PINTLE
LEAD SCREW
Figure 7-31 - Idle Air Control (IAC) Valve (TBI 220)
Throttle Position Sensor UPS)
The throttle position sensor (TPS), is mounted on the
side of the throttle body opposite the throttle lever
assembly. Its function is to sense the current throttle
valve position and relay that information to the ECM
(see Figure 7-32). Throttle position information allows
the ECM to generate the required injection control
signals (base pulse).
If the TPS senses a wide open throttle, a voltage signal
indicating this condition is sent to the ECM. The ECM
then increases the injector base pulse width, permitting
increased fuel flow.
As the throttle valve rotates in response to movement
of the accelerator pedal, the throttle shaft transfers
this rotation movement to the TPS. A potentiometer
(variable resistor) within the TPS assembly changes its
resistance (and voltage drop) in proportion to throttle
movement.
THROTTLE VALVE
ENGINE CONTROL MODULE (ECM) i
THROTTLE POSiT10N AT
SENSOR (TPS)
e
Figure 7-32 - Throttle Position Sensor (17BI 220)
FUEL PUMP CIRCUIT
SECTION 7D ,
By applying a reference voltage (5.0 volts) to the TIPS
input, a varying voltage (reflecting throttle position) is
available at the TPS output . For example, approximately
2.5 volts results from a 50% throttle valve
opening (depending on TIPS calibration). The voltage
output from the TPS assembly is routed to the ECM for
use in determining throttle position.
The fuel pump' is a turbine type, low pressure electric
pump, mounted in the fuel tank. Fuel is pumped at a
positive pressure (above 62 kPa or 9 psi) from the fuel
pump through the in-line filter to the pressure regulator
in the TBI unit (see Figure 7-25). Excess fuel is returned
to the fuel tank through the fuel return line.
The fuel pump is attached to the fuel gage sender
assembly. A fuel strainer is attached to the fuel pump
inlet line and prevents dirt particles from entering the
fuel line and tends to separate water from the fuel.
Vapor lock problems are reduced when using an electric
pump because the fuel is pushed from the tank
under pressure rather than being pulled under vacuum,
a condition that produces vapor.
When the key is furst turned "ON" without the engine
running, the ECM turns a fuel pump relay "ON" for two
seconds. This builds up the fuel pressure quickly. If
the engine is not started within two seconds, the ECM
shuts the fuel pump "OFF" and waits until the engine
starts . As soon as the engine is cranked, the ECM
turns the relay "ON" and runs the fuel pump.
On the 5.7L engine in the G van and all other 5.7L or
7.4L engines in vehicles over 8500 GVW, a fuel module
will override the ECM and the fuel pump will run for approximately
twenty seconds. The fuel module corrects
a hot restart (vapor lock) during a high ambient condition.
ENGINE FUEL SYSTEMS
When the engine is cranking or running, the ECM
receives distributor reference pulses which in turn
energize the fuel injectors.
As a backup system to the fuel pump relay, the fuel
pump can also be turned on by an oil pressure switch .
When the engine oil pressure reaches about 28 kPa (4
psi), through cranking and the fuel pump relay does
not complete the circuit, the oil pressure switch will
close to complete the circuit to run the fuel pump.
An inoperative fuel pump relay can result in long
cranking times, particularly if the engine is cold. The
oil pressure switch will turn on the fuel pump as soon
as oil pressure reaches about 28 kPa (4 psi).
FUEL FILTER PART #25055052 A-C GF 481
In-line Filter - located inside RF from rail
FUEL FILTER #25055052 GF481
25055129(48508)
3975550 (4852()
15530354(48520)
CAUTION :
Figure 7-33
To reduce the risk of fire and personal
injury, it is necessary to allow fuel
pressure to bleed off before servicing
fuel system components. (See "Fuel
System Pressure Relief Procedure.")
The in-line filter is located in the fuel feed line. It
prevents dirt from entering the TBI unit.
In-Tank Filter
A woven plastic filter is located on the lower end of the
fuel pickup tube in the fuel tank. The filter prevents dirt
from entering the fuel line and, also, stops water,
unless the filter becomes completely submerged in
water. This filter is self-cleaning and normally requires
no maintenance. Fuel stoppage, at this point, indicates
that the fuel tank contains an abnormal
amount of sediment or water; the tank should,
therefore, be thoroughly cleaned.
FUEL AND VAPOR PIPES
The fuel feed and return pipes and hoses extended
7-35
from the fuel pump and sender to the TBI unit. They are
secured with clamps and are routed along the frame
side member.
The vapor pipe and hoses extend from fuel pump and
sender unit to the evaporative emission control vapor
canister.
FUEL TANK
The fuel tank, at the rear of the underbody, is held in
place by two metal straps. Anti-squeak pieces are used
on top of the tank to reduce rattles.
Filler Neck
Fuel Filler Cap
SECTION 7D-ENGINE FUEL SYSTEMS
To help prevent refueling with leaded gasoline, the fuel
filler neck on a gasoline engine vehicle has a built-in
restrictor and deflector. The opening in the restrictor
will only admit the smaller unleaded gas nozzle spout,
which must be fully inserted to bypass the deflector.
Attempted refueling with a leaded gas nozzle, or
failure to fully insert the unleaded gas nozzle, will
result in gasoline splashing back out of the filler neck.
The fuel tank filler neck is equipped with a screw-type
cap. The threaded part of the cap requires several
turns counterclockwise to remove. The long threaded
area was designed to allow any remaining fuel tank
pressure to escape, while the cap was being removed.
A built-in torque-limiting device prevents overtightening
. To install, turn the cap clockwise until a clicking
noise is heard. This signals that the correct torque has
been reached and the cap is fully seated.
EVAPORATIVE EMISSION CONTROL
The system transfers fuel vapors from the fuel tank in-
Figure 7-34 - Diesel Engine Fuel System
7-36
to a vapor canister and then vapors are purged into the
intake manifold air flow and consumed in combustion.
DIESEL ENGINE
SYSTEM DESCRIPTION
The 6.2-liter diesel engine fuel system is composed of:
" Fuel tank with water sensor and screen filter
" Primary fuel filter
" Mechanical fuel pump
" Secondary fuel filter
" Fuel line heater
Injection distributor pump
" High pressure lines
" Fuel injection nozzles.
Fuel is pulled from the fuel tank by the mechanical pump
which is located on the right side of the engine. It is driven
by an eccentric lobe on the camshaft through a pushrod.
Fuel is pulled through the primary filter, by the mechanical
pump. Fuel is then pumped through the fuel line heater
and through the secondary filter mounted on the inlet manifold.
Both filters remove foreign material which could
damage the injection pump or clog the injector nozzle.
From the filter, the fuel is pumped to the injection pump.
(See Figure 7-25.)
The 6.2-liter injection pump is mounted on top of the engine
under the intake manifold . It is gear driven by two
gears - one attached to the front end of the camshaft
which drives the second gear that is attached to the end
of the injection pump shaft. These two gears are the same
size and have the same number of teeth ; thus, the injection
pump shaft turns at the same rate as the camshaft
and one-half the speed of the crankshaft. The pump will
turn in the opposite direction to that of the camshaft and
crankshaft.
INJECTOR
NOZZLES (8)
INJECTOR PUMP
SECONDARY FILTER - VARIES BY MODEL & YEAR
(AC PART NO. TP943 - SPIN-ON TYPE)
(AC PART NO. T936 - SQUARE-SHAPED TYPE)
PRIMARY FUEL FILTER
(AC PART NO. T944)
WATER
DRAIN
SIPHON
VALVE
SECTION 7D
The injbction pump is a high-pressure rotary-type pump
that directs a metered, pressurized fuel through the high
pressure tubes to the eight injector nozzles . The eight
high pressure lines are all the same length although their
shapes may be different. This prevents any difference in
timing, cylinder to cylinder.
The fuel line heater operates when the ambient temperature
is low enough to require heating of the fuel.
MAINTENANCE AND INSPECTION
WATER IN FUEL
The diesel engine has a "water-in-fuel" warning system
allowing the user to guard against water in fuel, which is
very critical in diesel engines.
The fuel tank is equipped with a filter which screens out
the water and lets it lay in the bottom of the tank below
the fuel pickup. When the water level reaches a point
where it could be drawn into the system, a warning light
flashes in the cab. A siphoning system starting at the tank
and going to the rear spring hanger on some models and
at the midway point of the right frame rail on other models
permits the user to attach a hose at the shut-off and siphon
out the water.
A primary filter (Figure 7-26) is located on the front of the
dash and it also has water-draining provisions.
A secondary in-line fuel filter (Figure 7-27) is the final filter
before fuel enters the injection-pump .
See Appendix 7-8 - Secondary Fuel Filters at the back
of this section of the manual for additional equipment operation
information.
When changing the fuel filter or when the vehicle has run
out of fuel, disconnect the connector .from the temperature
switch and jumper connector terminals . This will aid in
purging air from the pump. (This procedure is necessary
only on a hot engine, as the circuit will always be closed
when the engine is cold.)
PRIMARY FUEL FILTER WATER DRAIN
If it should become necessary to drain water from the fuel
tank, check the primary fuel filter (Figure 7-26) for water.
This can be done as follows :
1 . Open the petcock on the top of the primary filter
housing.
2. Place a drain pan below the filter and open the petcock
on the bottom of the drain assembly. (A length of hose
is attached to the petcock to direct drained fluid below
the frame.)
3. When all water is drained from the filter, close the
petcock firmly.
ENGINE FUEL SYSTEMS
7-37
PRIMARY FUEL
FILTER (MOUNTED
ON FRAME RAIL -
P-SERIES)
Figure 7.35 - Primary Fuel Filter (AC Type T944)
30 FT. LBS.
4. Close the upper petcock tightly .
Figure 7-36 - Secondary Fuel Filter (AC Type TP943)
NOTE: If the filter is completely drained, remove the filter
and refill it with clean diesel fuel to prevent engine
stalling .
5. Start the engine and let it run briefly . The engine may
run roughly for a short time until the air is purged from
the system.
6. If the engine continues to run roughly, check that both
petcocks at the primary filter are closed tightly .
SECONDARY FUEL FILTER
(See Figure 7-27)
Removal
1 . Remove the fuel filter lines from the adapter.
2. Remove the fuel filter adapter from the intake manifold .
3. Remove the filter.
Installation
Anytime either of the fuel filters is removed or replaced,
refill it with clean diesel fuel to prevent engine stalling after
start-up, and to avoid very long engine cranking time.
1 . Install the filter to the adapter.
2. Install the adapter to the intake manifold .
3, Install the fuel filter lines.
SECTION 7D
DIESEL FUEL MANAGER/FILTER
ELEMENT REPACEMENT
6.5L MODEL FM 100
(See Figure 7-28)
Removal
1 . Remove the fuel filler cap to release any pressure or
vacuum in the fuel tank.
2. Remove the element nut (7) turning it by hand in a
counter-clockwise direction . If unable to turn by hand,
a strap wrench (oil filter type) may be used to "break
loose" the element nut .
3. Remove the element (8) by lifting it straight up and out
of the heade assembly (9). It is not unnecessary to drain
fuel from the header assembly (9) to change the filter
element (8) since the fuel will remain in the header
assembly's cavity.
Important
Make sure the mating surface between the element
assembly and the header assembly is clean before installation
.
Installation
1 . Install the new element assembly by aligning the widest
key slot located under the element assembly cap with
the widest key in the header assembly.
Push the element in a downwards direction until the
mating surfaces make contact .
2. Install the element nut (7).
ENGINE FUEL SYSTEMS
Tighten
9 Tighten the element nut (7) securely by hand.
1 . Bleed air from the fuel manager/filter as follows :
a. Open the air bleed valve on top of the fuel manager/
filter assembly.
b. Connect a hoseto the air bleed valve located on top
of the element assembly and place the other end of
the hose into a suitable container .
CAUTION: THE WATER/DIESEL FUEL MIXTURE IS
FLAMMABLE, AND COULD BE HOT. TO HELP AVOID
PERSONAL INJURY AND/OR PROPERTY DAMAGE,
DO NOTTOUCH THE FUEL COMING FROM THE DRAIN
HOSE, AND DO NOT EXPOSE THE FUEL TO OPEN
FLAMES OR SPARKS.
BE SURE YOU DO NOT OVERFILL THE CONTAINER.
HEAT (SUCH AS FROM THE ENGINE) CAN CAUSE THE
FUEL TO EXPAND. IF THE CONTAINER IS TOO FULL,
FUEL COULD BE FORCED OUT OF THE CONTAINER.
THIS COULD LEAD TO A FIRE AND THE RISK OF
PERSONAL INJURY AND/OR VEHICLE DAMAGE.
7. NUT, ELEMENT
8. ASSEMBLY, ELEMENT
9. ASSEMBLY, HEADER
10 . SEAL, WATER SENSOR
11 . ASSEMBLY, WATER SENSOR
12 . SCREW, SENSOR MOUNTING
14 . SEAL, CAP
15 . ASSEMBLY, HEATER
16. NUT, CAP
18. CAP, AIR BLEED
V2639
7-38
Figure 7-28 - Diesel Fuel Manager/Filter (6.5L)
c. Disconnect the fuel injection pump shut-down solenoid
wire .
d. Crank the engine in 10 to 15 second intervals until
clear fuel is observed at the air bleed hose (wait for
one minute between cranking intervals) .
e. Close the air bleed valve.
f. Connect the shut-down solenoid wire and reinstall
fuel filler cap.
Start the engine and allow to run for five minutes at
idle.
h. Check the fuel manager/filter for leaks.
9.
FUEL PUMP REPLACEMENT
(See Figure 7-29)
Removal
1 . Remove the negative (-) battery cable(s) .
2. Remove the electrical wiring from the pump.
3. Remove the harness from the pump support bracket .
4. Remove fuel lines from the pump.
0 Use two wrenches to remove the lines.
5. Remove the pump support bracket screws.
6 . Remove the support bracket from the brake lines.
7. Remove the pump and bracket from the frame rail.
Installation
1 . Install the pump and bracket to the frame rail.
2. Install the support bracket to the brake lines.
3. Install the pump support bracket screws.
4. Install the fuel lines to the pump.
Use two wrenches to install the lines.
5 . Install the wiring harness to the support bracket .
6. Install the electrical wiring to the pump.
7. Install the negative (-) battery cable(s) .
Inspect
Inspect thefuel lines between fuel filter and tank for
restrictions .
Inspect the fuel tank sending unit for restrictions .
If "OK" replace the fuel pump.
FUEL PUMP TESTS
SECTION 7D
If the fuel system is suspected of not delivering enough
fuel, it should be inspected as follows and both the "Fuel
Pump Flow Test" and the "Fuel Pump Pressure Test"
should be performed .
ENGINE FUEL SYSTEMS
7-38A
Figure 7-29 - Pump # 6442656 - Fuel Pump
Location
Make certain that there is sufficient fuel in the tank.
" Check for leaks at all fuel connections from the fuel
tank to the injection pump.
Tighten any loose connections .
With the engine running, check all hoses and lines
for flattening or kinks that would restrict the flow of
fuel .
" Air leaks or restrictions on the suction side of the fuel
pump will seriously affect pump output .
FUEL PUMP FLOW TEST
1 . Remove the fuel line at the fuel filter inlet.
2. Disconnect the fuel injection pump electric shut-off
solenoid wire (pink wire) .
3. Place a suitable container at the end of the fuel filter
inlet line.
4. Crank'the engine. for 15 seconds .
5. The fuel pump should supply 237 ml (1/2 pint) or more
in 15 seconds .
6. Install the fuel injection pump electric shut-off solenoid
wire (pink wire).
7. Install the fuel line at the fuel filter inlet.
0 If the system fails to pass the above test:
Inspect
Inspect the fuel lines between fuel filter and tank for
restrictions.
Inspect the fuel tank sending unit for restrictions .
If "OK" replace the fuel pump.
FUEL PUMP PRESSURE TEST
1 . Remove the fuel line at the fuel filter inlet.
SECTION 7D - ENGINE FUEL SYSTEMS
2 . Disconnect the fuel injection pump electric shut-off
solenoid wire (pink wire) .
3. Install a low pressure gage to the line.
4. Crank or run the engine for 10 to 15 seconds .
5. Fuel pressure should be 40 to 60 kPa (5.8 to 8.7 psi).
6. Connect the fuel injection pump electric shut-off solenoid
wire (pink wire) .
7. Install the fuel line at the fuel filter inlet.
If the system fails to pass the above test:
APPENDIX 7-6
PLUGGED FUEL RETURN LINE
AND ENGINE PERFORMANCE
The following information has been extracted from a
Chevrolet Dealer Service Technical Bulletin and concerns
poor engine performance due to a plugged fuel return line
on the G-30 Cutaway and P-Series Class A 'Rail.
Reference: Chevrolet Dealer Service Technical Bulletin
No. 78-I-53 (September, 1978)
Prior to Cutaway and Class A Rail body completion, a
temporary fuel tank was utilized and required that the fuel
return line remain disconnected and plugged.
The line was to be unplugged and connected by the body
builder prior to final delivery of the completed vehicle .
Failure to reconnect the fuel return line can cause a vapor
lock condition at high altitudes or high ambient
temperatures.
In the event of a lack of power or rough engine complaint
on the subject vehicles, check for the proper connection
of the fuel return line. (See Figure A7-6-1 .)
NOTE: , Some 1978 and 1979 "G" Vans with V-8 engines,
when operated in high ambient temperatures and
under high engine fuel demands, have experi
enced the deformation of the flexible hose which
connects the fuel feed line to the fuel pump. (See
Figure A7-6-1 .)
This condition is difficult to diagnose due to the unusual
conditions under which it takes place.
To prevent this hose from deforming, a new molded hose
(GM Part No. 14010036) has been released for 1980 production
and can also be used for service replacement.
Effective with 1980 model production, an improved flexible
hose was also introduced into production for the Class A
Motor Home chassis. The new hose resists "sucking shut"
in high heat and high fuel demand situations; however, it
still will draw closed if tank or line filters become plugged.
(GM Part No. 14026551 for 454 engines and GM Part No.
14026550 for 350 engines.)
FUEL PUMP
FUEL FEED 1 ASSEMBLY
FRONT PIPE
FUEL RETURN
FRONT PIPE
FUEL RETURN HOSE
(32) MODELS EXCEPT
DIESEL ENGINE
FigureA7-6-1-- Fuel Return Line Connections
VAPOR LOCK CAUSE AND CURE
The following information has been compiled from extensive
research and testing performed by Chevrolet Engineering
and RV manufacturers concerning fuel handling
problems of the Class A Motor Home (during 1982 and
1983) . Chevrolet and the RV manufacturers examined
typical "problem units" furnished by various owners in
order to better understand "real-world" vapor lock problems
in the highly customized Class A Motor Home and
develop corrective actions .
This information is presented as an aid to the motor home
owner in understanding the problems associated with vapor
lock and their suggested solutions .
Fuel System Plumbing
As determined from initial studies, Chevrolet engineers
and RV manufacturing representatives determined that
part of the problem concerning vapor lock involved the
RV manufacturers' approach to the fuel system plumbing.
Examination of problem units identified considerable
plumbing errors, such as :
" Four feet of rubber hose added in the middle of the
stretch chassis.
" A length of hose positioned over the top of the tank to
the pickup.
" Total rubber plumbing which is tied to the rear hot water
lines with zip straps so that there was a tendency for
the fuel to boil and the lines to "suck shut" or kink at
each zip strap.
" Vehicles equipped with a defective switch valve so that
the ports did not line up properly and some of the valves
would only switch occasionally. (Ports that did not line
up caused restriction as did units that had two additional
fuel filters and a stretch chassis. All of these factors
add to the load on the mechanical fuel pump.)
" An electric fuel pump installed in the return line rather
than the suction line.
Incorrect tank cap venting .
And so on.
Chevrolet and the RV manufacturers' representatives determined
that 100 percent of the motor homes produced
with . plumbing errors such as those above could have
vapor locking problems. Investigation showed that a properly
plumbed fuel system down the inside of the frame
rail was also not a 100 percent cure for the problem.
Fuel Properties
As part of the investigation, Chevrolet Fuel and Lubrication
Engineers conducted a nationwide survey examining
the possibility that fuels could cause vapor lock. Results
of the survey show that oil companies have contributed
APPENDIX 7.7
7-40
to the cause of vapor lock by the addition of alcohol to
the fuel without informing the public or advertising the fuel
as gasohol . Also, it was determined that butane was
added to "cover up" lower grade crudes and to increase
octane ratings . The result of the fuel being adjusted and
the octane modifiers was a general increase in the Reid
vapor pressure (RVP) of the fuels (the higher the Reid
vapor pressure the greater the possibility of vapor lock) .
The average Reid vapor pressure of regular unleaded
gasoline was 9.3 in 1980, 9.8 in 1981 and 10.3 in 1982
(with individual locations showing a reading of 12 and 13) .
With fuel changes toward the higher Reid vapor pressure
fuels, some motor home owners who have never experienced
any problems could have vapor lock problems
that did not exist a year or so ago . Also, it was determined
that mountains, steep grades and overloaded vehicles
tend to aggravate the vapor lock problem, as recorded
in a park survey at Pikes Peak. Vapor lock at Pikes
Peak is the single most recorded mechanical problem
encountered.
Results of Vapor Lock Investigation
During the week of October 17, 1983, Chevrolet invited
all Class A Motor Home manufacturers to the GM Proving
Grounds in Phoenix, Arizona. The purpose of this meeting
was to discuss the findings of the investigation into the
cause. of vapor lock and to make specific corrective recommendations
for current and future production vehicles
(including changes in truck emissions) . The meeting was
attended by 34 of 36 RV manufacturers . Chevrolet suggested
that the RV manufacturers incorporate the following
recommendations into current and future vehicle
building, as well as develop some adaptation for problem
units already existing in the field. The following recommendations
were presented :
A one-half inch steel fuel line mounted on the outside
of the frame rail, protected against rub and
chafe (see Figure A7-7-2) .
" Also recommended is a pump bypass line along
with a check valve. The 12-801 is a positive displacement
pump and will not allow fuel flow if it stops
running . The bypass, which closes under fuel
pressure, will allow the engine mounted mechanical
pump to pull fuel from the tank in the event of an
electric pump failure. (See figure A7-7-1) .
" The fuel requirements for the 454 engine at wideopen
throttle are 25 gallons per hour at 2 PSI
minimum and 3 PSI maximum. If fuel line lengths or
routings create a situation where this cannot be
met, an electric pump should be added at the fuel
tank to supply fuel to the mechanical pump on the
engine. Pressure in the supply line will further
reduce the chance of bubbles forming versus a
negative pressure situation with a mechanical
pump only. (See Pressurized Fuel System Diagnosis
Chart in Figure A7-7-8.)
VAPOR LOCK
CAUSE AND CURE (Cont'd)
" A single in-line filter should be placed between the tank
and the electric fuel pump. (One filter choice is AC Part
No . GF62C.)
" A 3/8-inch rubber fuel line connection should be made
at the mechanical fuel pump and at the fuel pump sending
unit.
" Power for the electric fuel pump should be controlled
through a relayorspecial oil pressureswitch to assure
shut-down in the event of vehicle upset (see Figure
A7-7-3). Consideration could be given to a manual
priming override in the event the system has totally
run out of fuel. Normal starts would occur with the
fuel remaining in the carburetor and upon starting
as oil pressure came up the special switch or relay
and would turn on the electric pump. (See installation
instructions in Figure A7-7-4.)
" AC electric fuel pump (AC Part No. EP89) can also be
used and does not require a fuel pressure regulator .
The wiring remains the same.
Chevrolet invited all RV manufacturers to the Phoenix
meeting to share the findings and test information, as it
would be difficult for a singular RV manufacturer (or
customer) to produce these tests on their own. Chevrolet
informed the RV manufacturers that all necessary steps
would be taken to correct any vapor lock problem on any
chassis with a 137-, 158-, 178-inch wheelbase with a 100
percent factory system. As an additional commitment to
the 1983 meeting, Chevrolet has informed all RV manufacturers
that all necessary steps will be taken to correct
any vapor lock problem for the 208-inch wheelbase Model
CP32032 entering production for the 1988 model year with
a 100 percent factory system. Additionally, Chevrolet requested
that the RV manufacturers correct any field problems
that are reported to them on any units that have
been modified by the RV manufacturer - such as stretch
chassis, dual tanks, dual fuel, oversize tanks, etc ., as the
individual manufacturers are more knowledgeable of their
own systems and are in a better position to make their
own modifications for the various models, years and
options .
NOTE: Chevrolet has completed testing of a new 60-
gallon tank. With the start of 1985 production, new
fuel lines were installed on the outside of the
frame rail. In the spring of 1985, a complete system
was in production with in-tank electric pusher
pump and external regulator adjustable by the RV
manufacturer for an oversize wheelbase . (See
Figure A7-7-5.)
APPENDIX 7-7
7-41
Check Valve Installation
To install a fuel line anti-siphon check valve into the
system, a 3/8" bypass line must be installed around
the electric fuel pump and regulator (See Figure
A7-7-1.) The valve is manufactured by Aluminum
Fabricated Products (AFP 200) and must be fitted with
3/8" hose connector, available from Parker-Hannifin
Corporation (Part No. 126HBL-6-6.) These parts are
usually available from marine hardware suppliers.
Install as follows :
" Connect a 3/8" hose to the T's .
Install one 3/8" T-fitting in the fuel line between the
regulator and the mechanical fuel pump and one
3/8" T-fitting between the electric fuel pump and the
fuel tank.
If the bypass fuel line is already in place, remove
1-1/2,inches of 3/8 fuel line and insert check valve.
" Insert valve side in line toward mechanical fuel
pump; insert fitting side into line from fuel tank.
" Secure bypass line and valve with 3/8" hose clamps.
REGULATOR
To
MECHANICAL
FUEL PUMP
00°
o0i
3/8" TEE
CHECK VALVE
AFP200
ELECTRIC
FUEL PUMP
11/2 " 3/8' HOSE
FEMALE FITTING
PARKER N126HBL-66
FROM
FUEL
TANK
Figure A7-7-1
APPENDIX 7-7
VAPOR LOCK
CAUSE AND CURE (Cont'd)
3/8"
RUBBER
LINE
MECHANICAL
FUEL PUMP
1/2"
STEEL
LINE
3/8" ELECTRIC FUEL
RUBBER PUMP &
LINE REGULATOR
FUEL FILTER
Figure A7-7-2 - 1984 Recommended Field Fix
OIL PRESSURE
SWITCH
GM PART NO. 3986857
GM PART NO. CONNECTION
25036851
457874
14034354
IGNITION
+ 12V
NOTE: THE FOLLOWING OIL PRESSURE
SWITCHES CAN BE USED WITH OR
WITHOUT A RELAY SWITCH AND ARE
CAPABLE OF HANDLING CURRENT
DRAW REQUIREMENTS OF THE
HOLLEY GPH 110 (PART NO. 12-801)
MAX-PRESSURE PUMP.
1/8 - 27 DRYSEAL (NPTF)
1/8 - 27 DRYSEAL (NPTF)
1/4 - 18 DRYSEAL (NPTF)
RELAY SWITCH GM PART NO. 356284
ELECTRIC
FUEL PUMP
CONNECTOR 12101921 WITH LOCK 12010259
CAN BE USED AS THE ELECTRICAL
CONNECTION FOR EACH OF THESE
SWITCHES.
HOLLEY ALSO PRODUCES A SWITCH (PART
NO. 12-810) THAT DOES NOT REQUIRE A
RELAY.
Figure A7-7-3 - Electric Fuel PumpfOil Pressure Switch Relay
7-42
VAPOR LOCK
CAUSE AND CURE (Cont'd)
GROUND ELECTRIC
PUMP
OIL PRESSURE
SWITCH
COIL
TO
ACCESSORIES
Figure A7-7-4 - Oil Pressure Switch - Typical Wiring Diagram
INSTALLATION INSTRUCTIONS
NOTE: Please read instructions completely before making
installation .
1 . Disconnect cable from battery.
2. Remove original equipment oil pressure switch and
retain .
3. Screw a 1/8-inch pipe nipple into the hole from which
the pressure switch was removed . Use any suitable
thread sealant on all fittings, taking care to avoid an
excess which might contaminate the engine.
4. Screw a 1/8-inch pipe tee onto the nipple and position
it in a manner to facilitate the installation of the original
oil pressure switch and the new fuel pump pressure
switch in the remaining two holes.
5. Screw in the two switches and reconnect the lead to
the original equipment oil pressure switch .
APPENDIX 7-7
7-43
NOTE: The pump oil pressure switch will normally have
three terminals marked: C (common), NC (normally
closed), and NO (normally open) .
6. Connect the fuel pump (black lead) to the terminal
marked "C." In this line, add an in-line fuse holder and
a 7.5-amp fuse.
7. Connect the terminal marked "NO" to the ON terminal
of the ignition switch .
8. Connect the terminal marked "NC" to the starter motor
circuit.
9. To complete the installation, connect the ground cable
to the battery.
BE SURE TO CRIMP SECURELY ALL ELECTRICAL
CONNECTORS AND CLEAN ANY AREA WHERE
GROUND LEADS WILL BE FASTENED.
1/2-INCH
RUBBER LINE
GM PART NO. 15530403
MECHANICAL
FUEL PUMP
ENGINE ELECTRICAL RELAY
GM PART NO. 15528707
OIL PRESSURE SWITCH
SEE 1 .800 GROUP
FORWARD LINE NS
REAR LINE NS
NOTE : In July, 1985, GM began production of a new
pressurized fuel system. From production, the RV
manufacturer may choose a 40-gallon standard
system, an optional 60-gallon system (Option No.
NN4) or specify Option No. 9H2. Option No. 9H2
deletes Chevrolet's system and requires the manufacturer
to install its own system . Check the
Service Parts Identification Label for appropriate
option number. See page 1-3.
APPENDIX 7-7
VAPOR LOCK
CAUSE AND CURE (Cont'd)
1985 112 THRU 1989 PRODUCTION SYSTEM
FUEL FILTER
GM PART NO. 25055347
AC TYPE GF-509
1/2 INCH
STEEL
LINE
REGULATOR
GM PART NO. 15598336 .
Figure A7-7-5 - 1985 112 to 1989 Pressurized Fuel System Components
HI PRESSURE HOSE
GM PART NO.:
15530451-40 GAL.
15530401-60 GAL.
40 GAL. TANK GM PART NO. 14042352
60 GAL. TANK GM PART NO. 14042378
40 GAL. IN TANK PUMP GM PART NO. 6472311
60 GAL. IN TANK PUMP GM PART NO. 6472526
40 GAL. TANK STRAPS GM PART NO. 472286
60 GAL. TANK STRAPS GM PART NO. 15597850
NOTE : The factory electric in-tank fuel pump has an activating
relay that is shipped loose in the parts
box to the RV manufacturer. The wire harness is
located at the left front corner of the engine compartment.
There are two studs on the engine side
of the tow pan for mounting the relay. See Figure
A7-17-2 for mounting location.
Figure A7-7-6
NOTE: Viton hose and clamp Kit #25028041 for short
hose between electric fuel pump and fuel
meter in tank.
Fuel Hoses 1990-92
Pressure line tank to rail line 15666408
Pressure line, rail to injector 15613689
Return line, injector to rail line 15613690
Return line, rail line to tank 15666409
Temporary fuel line usage was eliminated SOP 5-31-91 .
APPENDIX 7-7
VAPOR LOCK
CAUSE AND CURE (Cont'd)
11:411M'101i
ENGINE ELECTRICAL RELAY
GM PART #10052954
OIL PRESSURE SWITCH
SEE 1 .800 GROUP
FUEL LINES NS
FUEL TANK OPTIONS
STD. 40 GALLON
NN4 60 GALLON
NJ9 80 GALLON RH OR LH FILL
1990-1993 PRODUCTION SYSTEM FUEL INJECTION
FUEL FILTER
GM PART NO. 25055052
AC TYPE GF481
FUEL LINES RUN
INSIDE OF FRAME
40 GAL. FUEL SENDER GM PART NO. 25094633 PEW
60 GAL. FUEL SENDER GM PART NO. 25094631 PEX
80 GAL. FUEL SENDER GM PART NO. 25094783 PEY
FUEL SENDER TO TANK SEAL GM PART NO. 3893116
FUEL PUMP FITS ALL 3 GM PART NO. 6472763
FUEL IN TANK FILTER GM PART NO. 25055455
1994
40 GAL. WITH PUMP GM PART NO. 25028266
60 GAL. WITH PUMP GM PART NO. 25028269
80 GAL. WITH PUMP GM PART NO. 25028272
PUMP ONLY GASGM PART NO. 6443146
DIESEL METEOR ONLY
40 GAL. GM PART NO. 25027045
60 GAL. GM PART NO. 25004132
80 GAL. GM PART NO. 25029695
LIFT PUMP
1994 7.4 GAS
40 GAL. FUEL SENDER GM PART NO. 25028266
60 GAL. FUEL SENDER GM PART NO. 25028269
80 GAL. FUEL SENDER GM PART NO. 25028272
FUEL PUMP GM PART NO. 6443146
1994 6.2 DIESEL
40 GAL. FUEL SENDER GM PART NO. 25027045
60 GAL. FUEL SENDER GM PART NO. 25004132
80 GAL. FUEL SENDER GM PART NO. 25029695
LIFT PUMP GM PART NO. 6442656
APPENDIX 7-7
VAPOR LOCK
CAUSE. AND CURE (Cont'd)
m
Figure A7-7-7 - Engine Electrical Fuel Pump Relay - Typical Wiring Diagram
NOTE: Without activation of the electric in-tank fuel
pump, the chances for a vapor lock in the system
increases because of the increased workload on
the mechanical pump through the electric pump.
To check the system, perform the following operational
test. Turn the ignition key to the RUN
position. Have an assistant check (listen/feel) the
tank end for pump operation as a capacitor
charges in the relay. The pump will run for approximately
five seconds after the key has been
turned. (Twelve volts is also supplied to the pump
in the crank position and as the engine starts and
oil pressure builds, 12 volts is supplied to the
electric fuel pump whenever the engine is
running.)
VAPOR LOCK
CAUSE AND CURE (Cont'd)
1985 112 Through 1989 Model Year
Verify that the coach was built with a Chevrolet fuel
tank or that it contains an electric intank fuel pump.
This can be done by checking the invoices or Service
Parts I.D. Label . A 40-gallon tank is standard. Option
NN4 indicates a 60-gallon tank was installed . Option
9H2 indicates that the fuel system was installed by the
coach builder and may not be of Chevrolet design.
Once the system has been identified, determine that
the electric fuel pump is operating, as follows.
" With transmission in PARK position and emergency
brake ON, turn ignition ON. DO NOT START
ENGINE.
" Have someone hold their hand against the bottom
of the fuel tank.
" A vibration should be felt on the hand for approximately
5 seconds after the ignition is turned on.
If the pump does not operate, and a vibration is not
felt, check the fuel pump relay system wiring (see page
7-43 and 7-96 for location) . Check electrical continuity
from electric fuel pump relay (Fig. A7-7-3) to oil
pressure switch and from oil pressure switch to electric
fuel pump.
It is the responsibility of the coach manufacturer to in-
APPENDIX 7.7
sure that the electric fuel pump operates properly at
time of coach assembly.
If the coach does not have an electric fuel pump, or
was built before 1985 1/2, use the diagnostic chart on
page 7-48.
Gas Fumes in Engine Compartment or
Fuel in Charcoal Canister
1 . Remove line from charcoal canister that runs to the
fuel tank.
2. Remove gas cap from filler spout.
3. Blow air into disconnected canister line (Tank must
be at least 1/4 full.)
4. Listen at spout for bubbles in the fuel tank.
5. If air bubbles in gasoline, the lines are crossed .
This condition usually occurs when the coach manufacturer
has stretched the frame and the fuel lines
have been extended. Look for a crossed line where the
fuel lines have been spliced .
If blowing air into the disconnected line does not
cause bubbles, check for damage to fuel lines, to the
canister, and the valve on top of canister. (Fig. 7-96)
APPENDIX 7-7
VAPOR LOCK
CAUSE AND CURE. (Cont'd)
PRESSURE 11/2 to 5 PSI
SYSTEM O.K. AT IDLE PRESSURE
ROAD TEST AND OBSERVE GAGE
AT PROBLEM ROAD SPEED
INSTALL PRESSURE GAGE AT CARE. RUN ENGINE AT IDLE.
EQUIPPED WITH ELECTRIC PUMP
AND RETURN LINE HOOKED UP
ADJUST OR INSTALL A PRESSURE
REGULATOR SET TO 45 PSI AT
ENGINE IDLE
EQUIPPED WITH ONLY
MECHANICAL PUMP
DISCONNECT RETURN LINE AT
MECHANICAL PUMP AND WITH A
TEMPORARY TEST HOSE RETURN
FUEL TO A GALLON JUG UNDER
PRESSURE AT CARIB . INLET
ABOVE 5 PSI
Figure A7-7-8 - Pressurized Fuel System Diagnosis Chart For Pre 1985 112 and Units
NOTE : Cool fresh air should be introduced through the
fresh air induction via hose from the front of the
radiator to the carburetor air cleaner snout. This
has proven effective in reducing fuel percolation
in the carburetor fuel bowl .
PRESSURE 11/2 to
5 PSI
PRESSURE
PRESSURE 0 to 1 1/2 PSI ABOVE 5 PSI,
VEHICLE
PRESSURE PRESSURE PRESSURE PRESSURE
11/2to5PSI ABOVE 5 PSI 11/2 to 5 PSI ABOVE 5 PSI
SYSTEM O.K . ADD ELECTRIC PUMP .
PROBLEM SUGGEST HOLLEY 12-801
ELSEWHERE PUMP WITH HOLLEY 12-810 PRESSURE SHUT-OFF SYSTEM DEFECTIVE RESTRICTED- REPLACE
SWITCH. INSTALL AC-GF62C NORMAL REGULATOR PINCHED MECHANICAL
FILTER PRIOR TO PUMP AND RETURN LINE PUMP,
REGULATOR . INSTALL AS BACK TO TANK (RESTRICTED
CLOSE TO TANK AS
ABOVE 5 PSI ORIFICE
POSSIBLE . REMOVE ANY RETURN INOTHER
LINE FILTERS SIDE PUMP)
BETWEEN TANK AND CARB . REPAIR-AIR
ADJUST REGULATOR TO PRESSURE
OBTAIN 4-5 PSI MECHANICAL DISCONNECT ELECTRIC TO PUMP SHOULD
PUMP INLET WITH ENGINE AND BYPASS PLUMBINGTANK TO EASILY BLOW PRESSURE
RUNNING AT IDLE AND WITH LINES TO MECHANICAL PUMP INTO TANK 11h to 5 PSI
RETURN LINE HOOKED UP
AND FUNCTIONAL : 454 ENGINE
REQUIRES HIGH-VOLUME
PUMP AS ENGINE CAN USE 25 FOLLOW RETURN LINE DIAGNOSIS RETEST WITH SYSTEM O.K .
GALLONS OF FUEL PER HOUR
FOR NONELECTRIC PUMP RETURN LINE
AT WOT. FUEL SUPPLY LINE RECONNECTED
SHOULD BE ROUTED OUTSIDE
THE FRAME RAIL FOR HEAT .
SHIELD . 1/2 INCH PREFERRED
WITH 3/8 INCH REDUCING
ENDS . RUN FULL LENGHT AS PRESSURE PRESSURE
SMOOTH AND UNBROKEN AS 11/2 to 5 PSI ABOVE 5 PSI
POSSIBLE SECURED FOR NO
CHAFE OR RUB . USE STEEL
LINES WITH RUBBER
CONNECTIONS AT ENDS. LINE TOO SYSTEM O.K . SMALL OR
STILL HAS A
RESTRICTION
APPENDIX 7-7
VAPOR LOCK
CAUSE AND CURE (Cont'd)
RECHECK, FUEL PUMP
FOR PRESSURE 4 1/2 TO
5 PSI AT IDLE
UNIT REPAIRED .
PRESSURE 0 PSI
INSTALL REMOTE PRESSURE GAUGE AT MECHANICAL FUEL PUMP
INLET LINE. RUN ENGINE AT IDLE .
s
12 VOLTS AT
BOTH TERMINALS
CHECK WIRING CIRCUIT FROM
RELAY TO ALL PRESSURE SWITCH
CHECK WIRING FROM RELAY TO ELECTRICAL
SENDER AT TANK. DRAIN TANK AND
REMOVE FUEL GAUGE AND PUMP - CHECK
AND OR REPLACE FUEL PUMP .
CAUTION: DO NOT TEST OR RUN FUEL
PUMP ON BENCH OR IN DRY FUEL TANK
- PUMP DAMAGE MAY RESULT - MUST BE
TESTED IN LIQUID .
PUMP RUNS - SET FUEL REGULATOR TO
4 1/2 to 5 PSI AT IDLE - ROAD TEST.
PRESSURE 4-5 PSI
SYSTEM OK AT IDLE
J
REPLACE FILTER AND
TEST AGAIN AT ROAD
SPEED 2-4 PSI
ADEQUATE.
CAUTION: Electric fuel pumps must never be tested
dry. Can cause premature pump failure if
not tested in liquid .
PRESSURE ABOVE 4-5 PSI
Figure A7-7-9 - Pressurized Fuel System Diagnostic Chart 1985 112 thru 1989
SEE NOTE PAGE 7-46
FUEL PUMP DIAGNOSIS . ROAD TEST AND OBSERVE GAUGE CHECK & ADJUST PRESSURE
CHECK FOR INOPERATIVE
FUEL PUMP .
AT PROBLEM ROAD SPEED REGULATOR TO 4 1/2 TO 5 PSI .
PRESSURE 2-4 PSI PRESSURE 0-2 PSI
PUMP INOPERATIVE-PERFORM UNABLE TO ADJUST -
FUEL PUMP RELAY SYSTEM REPLACE DEFECTIVE
DIAGNOSIS .
REGULATOR AND SET
A-KEY ON-5 SECONDS SYSTEM OK
AT 4 1/2 TO 5 PSI .
SHOULD HAVE CURRENT PROBLEM ELSEWHERE CHECK ADJUSTMENT
BOTH TERMINALS - IF ON FUEL REGULATOR
ONLY ONE TERMINAL HAS AND/OR CHECK FOR
12 VOLTS - REPLACE RELAY PLUGGED INLINE FUEL
#15528707 - LOCATION FILTER ON FRAME
SEE PAGE 7-102 . #GF 509
The following information is presented as an aid to the
motor home owner and RV manufacturers in understanding
some of the problems and the suggested solutions for
after-market fuel systems .
This information has been extracted from a GM field representative
research and testing report concerning problems
with after-market fuel systems. Chevrolet and RV
manufacturers examined typical "problem units" furnished
by various owners to better understand aftermarket
fuel system problems that are unknowingly built
into a fuel system.
GM has taken the position that any repairs to after-market
fuel systems will be the responsibility of the RV manufacturer
and/or the motor home owner. Problems associated
with the vehicle fuel system will not be corrected
under the GM warranty unless the system is a 100 percent
GM fuel tank and system . (For additional information, see
Appendix 7-7- Vapor Lock Cause and Cure referring to
the Chevrolet/RV Manufacturers meeting held in Phoenix,
Arizona, October, 1983.)
RESEARCH FINDINGS - Many RV manufacturer's
customer service representatives have experienced
customer complaints in several areas concerning aftermarket
fuel systems. The three overall complaints are :
1 . Raw fuel is spilled out the vent to the ground or fills
the charcoal canister .
2. The fuel tank fills slowly.
3. Raw fuel "shoots" from the tank when the fuel cap is
removed.
COMPLAINT No. 1 - The situation of raw fuel spilling
out the vent to the ground can only occur when the fuel
tank reaches a 100 percent "brim-full" condition . As there
is no air pocket in the top of the tank, the fuel expands
as it is heated and creates one of two possible situations.
Either the fuel tank itself will bulge due to the expansion
of the fuel, or the fuel escapes through the vent to the
ground or the charcoal canister at a rate that is controlled
by pressure and the size of the vent.
APPENDIX 7-8
TROUBLESHOOTING
AFTERMARKET FUEL SYSTEMS
COMPLAINT No. 2-The "slow fill" complaint occurs on
after-market fuel systems as the fuel entry point is positioned
midway on the side of tank. This is a design "tradeoff"
versus a top-fill or corner-fill fuel entry location. When
the level of the fuel covers the fill opening in the side of
the tank, the fill rate slows because the incoming fuel must
move or "displace" the existing fuel out of the way. Also,
the size of the vent and the spit-back tube have a bearing
on the rate of fuel fill . Even if the top of the fuel tank was
completely removed (similar in appearance to a pail), the
fill rate would still be very slow as the incoming fuel must
still move and displace the existing fuel .
EXAMPLE: Filling a fuel tank would be much easier by
pouring the fuel into the top to "splash" to the bottom
versus filling the tank by forcing the fuel at the bottom of
the pail which requires gravity to work against fluid weight
and displacement .
COMPLAINT No. 3 - Fuel "shooting" from the fuel tank
when the cap is removed is caused by the vent being too
small, and/or an incorrect position of the main side-fill fuel
entry tube and spit-back tube.
CASE STUDY EXAMPLE : An after-market fuel system
was fitted with a spit-back tube extending approximately
1-3/8 inches into the fuel tank based on a planning design
of 90 percent fill capacity of a tank 14 inches deep. (This
is not enough of a margin of air space for all applications.)
In this situation, when the fuel was above the half-way
point of the tank, fuel was in the tank filler neck at the
same level of the fuel in the tank. As the pressure increased
in the tank from heat expansion and slightly restricted
venting, the pressure was actually over the entire
surface of the fuel. The moment the filler cap was removed,
fuel rushed backward up the filler neck as the spitback
tube could not bleed off the pressure fast enough.
(This situation is similar to shaking a carbonated soft drink
to obtain maximum "fizz," then turning the bottle or can
upside down and opening the container slowly.)
With a top-fill or corner-fill tank, (even with a restricted
vent) the chance of fuel "spitting out" is greatly reduced
as fuel is not present in the fill neck. The worst problem
associated with a top-fill or corner-fill tank is air relief as
the cap is removed.
The problem of fuel "spit back" can be corrected for a
side fill tank IF the pressure is removed from the top of
the tank.
TO HELP CORRECT THIS CASE STUDY COMPLAINT:
A design change is necessary in the restriction size of the
vent line. As the size of the orifice is currently about a
.030-inch opening, the above case study system would
benefit by opening the vent hole to between .055 inch and
.060 inch. This would allow additional pressure to bleed
out of the top of the tank and to reduce downward pressure
on the surface of the fuel.
A restricted vent is needed for two reasons:
" The restricted vent is required to make the automatic
fuel shut-off work with the spit-back tube.
" The restricted vent also serves as an anti-siphon device
when the fuel runs to one end of the tank.
A restricted vent that is too large defeats the purpose of
the automatic shut-off and anti-siphon system. However,
a restricted vent that is too small invites excessive pressure
build-up in the tank.
APPENDIX 7-8
TROUBLESHOOTING
AFTERMARKET. FUEL
SYSTEMS (Cont1d)
Ideally, the spit-back tube should be positioned in the tank
to allow approximately 20 percent free air level. 'A top-fill
or corner-fill system should be considered with the fill pipe
extending into the tank to the same depth as the spit-back
tube and cut at an angle horizontal to the fluid level. This
remedy should be used in conjunction with a .055-inch to
.060-inch restricted vent and a GM-type fill cap.
ADDITIONAL TIPS - Troubleshooting after-market fuel
systems does not end with tank hardware. Generally,
pressure is a side effect of heated fuel causing expansion
and fume pressures . A service technician should also examine
the source(s) of the heat. Possible causes are:
" A hole in the exhaust blowing directly on the fuel tank.
" Serious overload or pulling of a trailer which puts abnormal
"fire" in the exhaust.
" An engine that is running poorly having higher than
normal unburned fuel in the exhaust system which is
burned off with the A.I.R. pump increasing exhaust
temperatures .
" An altered or modified exhaust system (by owner or RV
manufacturer) with an improper tank-to-pipe clearance.
SECONDARY FUEL FILTERS
The following information has been extracted from the GM
6.2-Liter Diesel Engine manual . The information covers
general operation, application and replacement part numbers
of both the Model 75 and Model 80 Secondary Fuel
Filter.
G-P SERIES-MODEL 75 SECONDARY
FUEL FILTER
The G-P Series uses a Stanadyne Model 75 secondary
fuel filter in 1983. (See Figure A7-9-1 .) It is fastened using
two ball clips. It is particularly important to place absorbent
towels under the filter when changing it to improve cylinder
and case valley drain and prevent fuel oil contamination
of the clutch-driven disc.
Figure A7-9-1 - Model 75 Secondary Fuel Filter
Figure A7-9-2- Relative Size of Micron Particles
APPENDIX 7.9
RELATIVE SIZE OF MICRON PARTICLES
MAGNIFICATION 1000 TIMES
1 MICRON = .000039 INCH
LOWEST VISIBILITY RANGE = 44 MICRONS ( .0017 INCH)
HUMAN HAIR = .003 INCH
.003 INCH
44 MICRONS
7-52
The Model 75 filter is a two-stage pleated paper type filter .
The first stage consists of approximately 400 square
inches of filtering area and will remove 94 percent of particles
10 microns or larger. The second stage is made of
the same paper material and consists of approximately
200 square inches of filtering surface . The second stage
is 98 percent effective in filtering the fuel already filtered
by the first stage.
Particles which are larger than 10 microns may damage
the pump's internal components. Figure A7-9-2 compares
various micron sizes and will, ultimately show the filter's
effectiveness .
G-P SERIES - MODEL 80 SECONDARY
FUEL FILTER
The Model 80 Stanadyne Fuel Filter provides the following
features in one unit:
" Two-stage fuel filter
" Fuel/water separator
" Electronic "water-in-fuel" signal
" Electric fuel heater
" Integral hand primer
" "Filter change" signal - removed starting 1989.
Fuel Heater
The purpose of the heater (see Figure A7-9-3) is to heat
fuel, so that the filter does not plug with paraffin wax
crystals. This will allow use of fuels at temperatures substantially
below the Cloud Point of the fuel. The heater is
electrically powered from the ignition circuit 39 and is thermostatically
controlled to work when waxing of the fuel is
expected.
The device can be divided into two major functional components
- the heater and the power control assemblies.
SECONDARY FUEL FILTERS
(Cont'd)
OPTIONAL
WATER DRAIN
LOCATION
FILTER
CHANGE
SIGNAL
CONNECTOR
"WATER IN FUEL"
WATER DRAIN \SIGNAL CONNECTOR
OPTIONAL WATER DRAIN
LOCATION
Figure A7-9-3 - Model 80 Fuel Filter and Base
Assembly
Fuel Filter
The engine fuel filter is a two-stage pleated paper type
filter (see Figure A7-9-4) . The first stage consists of approximately
350 square inches of filtering area and will
remove 96 percent of particles 5-6 microns or larger (see
Figure A7-9-2). The second stage is made of the same
paper material with glass particles and consists of approximately
100 square inches of filtering surface .
Figure A7-9-4 - Model 80 Filter Cross Section
APPENDIX 7-9
7-53
The second stage is 98 percent effective in filtering the
fuel already filtered by the first stage. Particles which are
larger than 10 microns may damage the pump's internal
components.
Water Sensor
The 6.21- uses a "water-in-fuel" warning system, which
allows the user to guard against water in the fuel.
The water is detected by a capacitive probe located in the
filter base. Electronics within the probe will connect a
ground (circuit 150) to the ground side of the "water-infuel"
lamp (circuit 508) . This lamp is in the center of the
instrument panel next to the glow plug lamp. In 1984
(4-wire water-sensor module) a bulb check was made
anytime the ignition switch was in the start position. A
"B+" signal on the purple wire at the "A" test switch
(Figure A7-9-5) causes pin "D" to pull low, grounding the
"water-in-fuel" bulb. In 1984-1/2 and 1985 (3-wire. watersensor
module) when the ignition is turned on, the lamp
will glow from 2 to 5 seconds, and fade away. This is done
as a bulb check.
'12VOLT D.C . SYSTEM
BAT. NEG. (GROUND)
BAT. POS. (SWITCHED)
SIGNAL LIGHT
BAT. POS. (SWITCHED)
TEST SWITCH
BAT. NEG.
BAT. POS. (SWITCHED)
SIGNAL LIGHT (250 mA MAX.)
Figure A7-9-5 - Filter Base Wiring
Water Separator
The bottom of the filter is a hollow water collector (Figure
A7-9-6) . Because of the greater density of water, the water
droplets will separate from the fuel oil . It will hold approximately
260 cubic centimeters of water (approximately
3-10 percent).
A nylon/fiberglass coalescent is used to blend the small
water droplets into larger ones.
Fuel Flow
SECONDARY FUEL FILTERS
(Cont'd)
See Figure A7-9-6 . Fuel enters at the top right inlet and
flows into the heating chamber. The heater is activated
at 8°C (46°F). and below. The heated fuel enters the element
at the top and flows down through the two-stage
WATER SENSOR
Figure A7-9-6-Filter and Base Flow Schematic .
APPENDIX 7-9
fuel filter media pack. While passing through the third
stage, water coalesces and drops to a sump holding area.
Clean fuel returns to the base and exits.to the fuel injection
pump. An electrical signal is obtained from the filterchange
sensor located in the return path.
SECTION 7E-ENGINE ELECTRICAL SYSTEM
ENGINE ELECTRICAL SYSTEM
The engine electrical system is separate from the motor
home "living" system . It consists of a chassis battery,
starting (cranking) system, charging system, ignition system
and instrument panel wiring and chassis information
gages.
BATTERY
GENERAL DESCRIPTION
The battery is a device designed to store electrical power
for later use. It performs this function through chemical _
action .
The battery has three major functions in the electrical
system. First, it is a source of electrical energy for starting
the engine. Second, it acts as a voltage stabilizer for the
electrical system . And third, it can, for a limited time, provide
energy when the electrical load exceeds the output
of the generator .
The sealed-top battery (Figure 7-28) is standard on all
vehicle lines.
BUILT-IN
HYDROMETER
Figure 7-28-Sealed-Top Battery
There are no vent plugs in the cover. The battery is completely
sealed, except for two small vent holes in the side.
These vent holes allow the small amount of gas produced
in the battery to escape. The sealed-top battery has the
following advantages over conventional batteries :
1 . No water addition for the life of the battery . This improvement
makes the sealed-top battery possible.
2. Overcharge protection. If too high a voltage level is
applied to the sealed-top battery, it will not accept as
much current as a conventional battery ; the excess
voltage will cause gassing, which leads to liquid loss.
7-55
3. Reduced self-discharge compared to a conventional
battery . This is important when a battery is left standing
for long periods of time.
4. Comparable power available in a lighter and smaller
case.
RATINGS
A battery has .two ratings : (1 .) a reserve capacity rating
at 80°F which is the time a fully charged battery will operate
the vehicle with no generator operation, (2.) a cold
crank rating at 0°F which indicates the cranking load capacity
. The Ampere/Hour rating formerly found on batteries
was based on the reserve capacity rating and is no
longer used.
MAINTENANCE AND INSPECTION
A battery is not designed to last indefinitely ; however, with
proper care, it will provide many years of service . If the
battery tests as "good" but fails to perform satisfactorily
in service, the following are some of the more important
factors that may point to the cause of the trouble .
1 . Accessories left on overnight.
2. Slow average driving speeds for short periods .
3. The vehicle's electrical load is more than the generator
output particularly with the addition of aftermarket
equipment such as radio equipment, air conditioning,
window defoggers or light systems .
4. Defects in the charging system such as electrical
shorts, slipping fan belt, faulty generator or voltage
regulator .
5. Battery abuse, including failure to keep the battery
cable terminals clean and tight or a loose battery (one
that is not securely held in place).
6. Batteries in vehicles stored for long periods of time
become discharged with sulfation occuring . Sulfation
of the plates reduces the battery's capacity for accepting
a charge. Also, under conditions of high ambient
temperature, the temperature of the electrolyte
may become excessive - causing boiling and loss of
electrolyte . See Appendix B - Preparing The Motor
Home For Storage for additional information concerning
battery storage damage.
NOTE : The inspection and test procedures which follow
apply for the Delco Sealed-Top Freedom Battery .
If your vehicle is equipped with a conventional
type and/or other brand battery, be sure to follow
the test procedure and specifications recommended
by the manufacturer.
VISUAL INSPECTION
The external condition of the battery should be checked
periodically for damage such as cracked cover or case
(Figure 7- 29) . Also check terminal area for loose or broken
parts.
HYDROMETER
CRACKED OR
BROKEN COVER
SECTION 7E -ENGINE ELECTRICAL SYSTEM
Figure 7-29-Visual Battery Inspection
,CRACKED OR
BROKEN CONTAINER
SIDE TERMINAL ADAPTER
(AC-DELCO PART ST1201)
CAUTION: BATTERIES PRODUCE EXPLOSIVE
GASES, CONTAIN CORROSIVE ACID, AND SUPPLY
LEVELS OF ELECTRICAL CURRENT HIGH ENOUGH
TO CAUSE BURNS. TO LESSEN THE CHANCE OF
PERSONAL INJURY, WHEN WORKING NEAR A
BATTERY:
" Always wear eye protection or shield your eyes. Do not
lean over a battery. Remove all metal jewelry.
" Never expose a battery to open flames or electric
sparks. Also, do not smoke near a battery.
" Do not allow battery acid to contact eyes or skin . Flush
any contacted area with water immediately and thoroughly.
Get medical help. Occasionally, a third condition may appear:
" Do not allow metal tools to contact both the positive
(red, "+") battery terminal (or any metal connected to
this terminal) and any other metal on either vehicle at
the same time. Make certain when attaching the jumper
cable clamps to the positive terminals of the batteries
that neither clamp contacts any other metal.
" Batteries should always be kept out of the reach of
children.
7-56
BUILT-IN HYDROMETER
(DELCO SEALED-TOP BATTERY)
The Delco sealed-top battery has a built-in temperaturecompensated
hydrometer in the top of the battery. This
hydrometer is to be used with the following diagnostic
procedure. When observing the hydrometer, make sure
that the battery has a clean top. A light may be required
in some poorly lit areas to see the right indication . Under
normal operation, two indications can be observed (Figure
7-30).
BATTERY TOP
Figure 7-30-Built-In Hydrometer
2.
GREEN DOT VISIBLE. Any green appearance is interpreted
as a green dot and the battery is ready for
testing. Do not charge the battery.
DARK - GREEN DOT NOT VISIBLE. If there is a
problem with cranking, the battery should be tested
following the Electrical Load Test in this section. But,
before testing, the battery must be recharged until the
green dot is visible . After charging, you may have to
shake or tilt the battery slightly for the green dot to
show.
NOTE: A battery that has sat in a completely discharged
condition or is extremely cold may not accept current
for several hours after starting the charger.
The charging and electrical systems should also
be checked at this time.
3. CLEAR OR LIGHT YELLOW. This means the fluid
level is below the bottom of the hydrometer. This may
have been caused by excessive or prolonged charging,
a broken case, excessive tipping or normal battery
wearout. When finding a battery in this condition, it
may indicate high charging voltage caused by a faulty
charging system and therefore, the charging and electrical
system may need to be checked. If a poor cranking
condition exists and is caused by the battery, it
should be replaced .
DARKENED DARKENED LIGHT
INDICATOR INDICATOR YELLOW OR
(WITH GREEN (NO GREEN BRIGHT
DOT) DOT) INDICATOR
MAY BE JUMP MAY BE JUMP DO NOT JUMP
STARTED STARTED START
SECTION 7E
CAUTION : DO NOT CHARGE OR TEST THE BATTERY
OR JUMP START THE VEHICLE WHEN THE HYDROMETER
IS CLEAR OR LIGHT YELLOW AS THIS COULD
RESULT IN PERSONAL INJURY (PARTICULARLY TO
EYES) OR PROPERTY DAMAGE FROM BATTERY EXPLOSION
OR BATTERY ACID. SEE CAUTION UNDER
"VISUAL INSPECTION" IN THIS SECTION OF THE
MANUAL.
ELECTRICAL LOAD TEST
(DELCO SEALED-TOP BATTERY)
Preliminary Steps
If the battery has been on charge, remove the surface
charge by connecting a 300-ampere load for 15
seconds.
CAUTION : SEE CAUTION UNDER "VISUAL INSPECTION"
IN THIS SECTION OF THE MANUAL.
If the battery is in the vehicle, attach the voltmeter leads
to the battery terminals . If the battery is out of the vehicle,
attach the voltmeter leads to the side terminal
adapters (AC-Delco Part ST-1201 or GM Part No.
1846855) on the battery . For Delco heavy-duty batteries
with threaded stud terminals, attach the voltmeter leads
to the snug-fitted terminal adapter ST-1201 ; or if not
available, attach the leads between the lead pad and
the bottom of the terminal hex nut.
Test Procedure
1 . Connect the voltmeter (preliminary steps) and apply
the test load to the value printed on the battery label .
2. Read the voltage after 15 seconds with the load
connected.
3. Disconnect the load and compare the voltage reading
with the chart in Figure 7-31 . If the voltage is less than
the reading specified in the chart, replace the battery .
If the reading is equal to or greater than that specified
in the chart, the battery is good .
NOTE : Refer to battery top for additional load test
amperes.
JUMP STARTING - WITH AUXILIARY
(BOOSTER) BATTERY
NOTE: Do not push or tow the vehicle to start it. There
are no provisions in the GM automatic transmission
for engagement of the transmission to turn
over the engine. Efforts to push or tow the vehicle
to start it will have no effect .
Both the booster and the discharged battery should be
treated carefully when using jumper cables. Follow the
conditions and procedure outlined below, being careful
not to cause sparks.
ENGINE ELECTRICAL SYSTEM
7-57
Figure 7-31 - Battery Test Load Table and
Voltage Drop Chart
CAUTION: FAILURE TO OBSERVE THESE CONDITIONS
OR PROCEDURES COULD RESULT IN SERIOUS
PERSONAL INJURY (PARTICULARLY TO EYES)
OR PROPERTY DAMAGE FROM SUCH CAUSES AS
BATTERY ACID, A BATTERY EXPLOSION, ELECTRICAL
BURNS AND/OR DAMAGE TO ELECTRONIC
COMPONENTS OF EITHER VEHICLE INVOLVED. SEE
CAUTION UNDER "VISUAL INSPECTION" IN THIS
SECTION OF THE MANUAL. IN ADDITION:
Be sure the jumper cables and clamps to be used for
jump starting do not have loose or missing insulation.
Do not proceed if suitable cables are not available .
If either battery has filler caps, check the fluid level. (Do
not check using an open flame). If low, fill to the proper
level with clear drinking water. Replace all caps before
jump starting.
Do not route the cable (or attach the clamp) on or near
pulleys, fans, or 'other parts that will move when the
engine is started .
Follow the procedure listed below for jump starting the
vehicle with an auxiliary booster battery .
1 . Set the parking brake firmly and place the automatic
transmission in PARK (NEUTRAL for manual transmission).
Turn off the ignition, turn off lights, and all
other electrical loads.
2. Check the built-in hydrometer. If it is clear or light yellow,
replace the battery, do not attempt to jump start.
3. Only 12-volt batteries can be used to start the engine.
BATTERY TEST LOAD (AMPS.)
692, 83-50 150
693, 83-60 180
695, 87A-60 230
696, 89A-60 270
Load Test Values
MINIMUM VOLTAGE TEMPERATURE (°F)
9.6 70
9.5 60
9.4 50
9.3 40
9.1 30
8.9 20
8.7 10
8.5 0
_
Minimum Voltage Dro
SECTION 7E-ENGINE ELECTRICAL SYSTEM
MON
DISCHARGED
BATTERY
SECOND
JUMPER CABLE
DO NOT ALLOW
VEHICLES TO TOUCH!
FIRST JUMPER CABLE
MAKE LAST
CONNECTION ON
ENGINE, AWAY
FROM BATTERY
BATTERY IN VEHICLE
WITH CHARGED BATTERY
Figure 7-32-Jump Start Cable Connections
NOTE: When jump starting a diesel engine vehicle with
charging equipment, be sure equipment used is
12-volt and negative-ground. Do not use 24-volt
charging equipment. Using such equipment can
cause serious damage to the electrical system or
electronic parts.
4. Attach the end of one jumper cable to the positive
terminal of the booster battery and the other end of
the same cable to the positive terminal of the discharged
battery (Figure 7-32). Do not permit vehicles
to touch each other as this could cause a ground connection
and counteract the benefits of this procedure .
5. Attach one end of the remaining negative cable to the
negative terminal of the booster battery, and the other
end to a solid engine ground (such~as A/C compressor
bracket or generator mounting bracket) at least 18
inches from the battery of the vehicle being started .
DO NOT CONNECT DIRECTLY TO THE NEGATIVE
TERMINAL OF THE DEAD BATTERY.
6. Start the engine of the vehicle that is providing the
jump start and turn off electrical accessories . Then
start the engine in the vehicle with the discharged
battery .
7. Reverse these directions exactly when removing the
jumper cables. The negative cable must be disconnected
from the engine that was jump started first.
MULTI-BATTERY ELECTRONIC JUMP
STARTING AID
Many RV manufacturers have built into their systems an
"emergency start button" on the dashboard that electrically
connects the coach batteries to the chassis battery .
The purpose of this starting aid is to create an "automatic
jump start." The motor home owner should be aware of
the possible problems this system may create, such as:
Many motor home owners, as a matter of habit, push
the "emergency start button" with EACH start under the
mistaken belief that three batteries are stronger than
one. Without knowing the actual condition of the RV
batteries, this action could unknowingly create "dead"
or undercharged batteries . If the charge state of the RV
battery is LOWER than the chassis battery, then within
a few seconds after pushing the start button on the
dash both the RV battery and the chassis battery become
equal and the motor home owner is then dealing
with two or three undercharged batteries .
Rapid discharge, to equalize the state of charge between
the batteries over a few seconds, is very hard
on the batteries . Often, the only "hold back" to this is
the connecting wire size . However, if the wires are small
enough to slow the rate of discharge to avoid battery
damage, then the wires can become overheated from
carrying too much amperage. This situation presents a
potential electrical failure and/or fire damage.
" Each time that the "emergency start button" is pushed,
an electrical solenoid switch closes under the hood.
Each time this solenoid switch closes, an electric spark
arc occurs. Each time this spark arc occurs, a high
resistance builds through the copper-to-copper contacts
and reduces the overall effectiveness of the
switch. In some cases (with severe battery electrical
differential) the switch contacts have "stuck" after being
used only once. This situation bypasses the isolator
and effectively renders the battery isolator system
useless.
Over the last few years, RV manufacturers have improved
these "emergency start button" systems through the use
of solid state technology. The application of this solid state
technology has appeared to solve the problems associated
with the earlier systems . The new system electronically
monitors the condition of the RV battery vs. the
chassis battery . If the chassis battery has a LOWER state
of charge than the RV battery, a light on the dashboard
will glow indicating that the "automatic jump start" system
has kicked in automatically without the driver physically
pushing the button. If the RV batteries are LOWER than
the chassis battery, the system will not allow an electrical
flow to occur between the batteries .
SECTION 7E ENGINE ELECTRICAL SYSTEM
ACTIVATED INDICATOR
(ON INSTRUMENT PANEL)
NOTE: IF AVAILABLE, USE DEEP
CYCLE AUXILIARY BATTERIES
GENERATOR
(PRE-1987 TYPICAL)
FROM
STARTER
SWITCH
ISOLATOR
(120 AMP TYPICAL)
CIRCUIT BREAKER
(80 AMP TYPICAL RECOMMENDED)
AUXILIARY LOAD
AUXILIARY
BATTERIES
AUXILIARY
BATTERIES
Figure 7-33- Typical Multi-Battery Electronic Starting Aid Wiring Diagram
These fully automatic electronic starting aids allow a current
to flow only to the starter motor thereby eliminating
battery equalization . This helps to eliminate battery damage
and a shortened battery life. A wiring diagram of a
typical multi-battery electronic starting aid is shown in
Figure 7-33.
BATTERY REMOVAL AND REPLACEMENT
When handling a battery, the following safety precautions
should be observed:
1 . Hydrogen gas is produced by the battery . A flame or
spark near the battery may cause the gas to ignite .
2. Battery fluid is highly acidic . Avoid spilling on clothing
or other fabric. Any spilled electrolyte should be flushed
with large quantities of water and cleaned immediately .
7-59 .
To remove or replace a battery, always disconnect the
negative cable first, then the positive cable. Torque the
battery cables at battery to 9 ft. lbs.
NOTE: See Appendix 7-10 at the back of this section of
the manual for additional information concerning
battery replacement.
STARTING (CRANKING) SYSTEM
The starter on the motor home chassis requires no maintenance.
It will provide years of service if proper cranking
procedures are used. When starting an engine, never
crank the starter longer than 30 seconds and allow at
least 15 seconds between starting attempts . This will help
keep the starter from overheating .
SECTION 7E
NEUTRAL
START
SWITCH
(WITH AUTOMATIC TRANSMISSIONS)
FLYWHEEL
Figure 7-34 -Starting Circuit
GENERAL DESCRIPTION
The function of the starting system is to rotate the engine
crankshaft at sufficient speed for ignition and the start of
engine operation. This it does by means of the starting
circuit which-consists of the battery, starting motor, ignition
switch, and the related electrical wiring . In addition, vehicles
with automatic transmissions have a neutral start
switch which prevents the engine from being started in
Any transmission selector lever position other than
NEUTRAL, or PARK. These components are connected
electrically as shown in Figure 7-34.
When the ignition switch is turned to START, electrical
current flows from the battery through the key switch,
neutral start switch and through the starter switch to
ground. Inside the starter switch, current flow from this
Figure 7-35 -10MT Starting Motor
ENGINE ELECTRICAL SYSTEM
7-60
control circuit activates the solenoid which closes the circuit
between the battery and the starting motor. The solenoid
also moves the starter drive gear into contact with
the crankshaft ring gear.
Three types of starter motors are used. The first, referred
to as the 10MT series, is shown in Figure 7-35 . The
second type, referred to as the 27MT series, is used on
diesel-equipped engines. The main difference is that the
27MT has a center bearing .
NOTE: The 1994 454 motor home starter will be a per-
' manent magnet type planetary gear reduction
starter designated as PG260. It provides better
performance quality and reliability in a smaller
starter motor.
SWITCH
TERMINAL
SOLENOID
RISER BARS CONDUCTORS
TO RISER BARS
TO ARMATURE
SECTION 7E -ENGINE ELECTRICAL SYSTEM
Certain starting motors have the shift lever mechanism
and the solenoid plunger enclosed in the drive housing,
protecting them from exposure to dirt, icing conditions and
splashing.
PULL-IN COIL
HOLD-IN COIL
PLUNGER
SOLENOID
ASSEMBLY
DISENGAGED
CURRENT FROM
STARTER SWITCH
COMPRESSION SPRING
FOR BUTT ENGAGEMENTS
PINION PARTIALLY ENGAGED
CURRENT
FROM BATTERY
OVER-RUNNING CLUTCH
FLYWHEEL
PINION FULLY ENGAGED AND
STARTER MOTOR CRANKING
Figure 7-36 -Solenoid Electrical Operation
7-61
In the basic circuit shown in Figure 7-34, the solenoid
windings are energized when the switch is closed. The
resulting plunger and shift lever movement causes the
pinion to engage the engine flywheel ring gear and the
solenoid main contacts to close and cranking takes place.
When the engine starts, pinion overrun protects the armature
from excessive speed until the switch is opened,
at which time the return spring causes the pinion to disengage.
To prevent excessive overrun, the switch should
be opened immediately when the engine starts .
The electrical operation of the solenoid is shown in Figure
7-36. The top illustration shows the starter disengaged.
The center drawing depicts the pinion partially engaged
with the pull-in coil and the hold-in coil activated . The
bottom view shows the pinion fully engaged and the starter
motor cranking with only the hold-in coil functioning .
MAINTENANCE AND INSPECTION
While the starter motor does not require maintenance, the
system wiring should be inspected periodically for damage
or corrosion . Inspect all connections to the starting motor,
solenoid, ignition switch, neutral start switch and battery,
including all ground connections . Clean and tighten all
connections as required .
If there appears to be a problem with the starting system
and the battery, wiring and- switches are in satisfactory
condition and the engine is known to be functioning properly,
refer to the appropriate shop manual for more detailed
diagnosis and test procedures.
STARTING PROBLEMS (HIGH AMBIENT
TEMPERATURES)
Under some conditions of high ambient temperatures,
when the engine has been turned off and the vehicle
allowed to set for 10 to 15 minutes, it is possible to encounter
a problem with the starter motor not activating
when you attempt to restart the engine. This possibility
occurs more frequently with the 7.41- engine when high
engine compartment temperatures and the radiated heat
from the exhaust pipe cause high resistance in the coil
wires of the starter solenoid. This high resistance reduces
current flow preventing activation of the solenoid and
starter motor. After the engine has cooled down sufficiently,
the starter motor should activitate properly upon
restart.
STARTING PROBLEMS (POOR GROUND)
The P-Series motor home is equipped with a webbed
ground strap that runs from the rear of the left cylinder
head to the frame. To improve electrical contact, remove
the strap from both connections. Scrape the (production)
paint from both the cylinder head and the vehicle frame,
connections. Add a star washer between the cylinder head
connection and the strap and between the vehicle frame
connection and the strap. Replace the strap and tighten
attaching bolts securely .
SECTION 7E
Refer to Appendix 7-12- "Hot Start" Problem Conditions
and Appendix 7-13 - Starter Motor Engagement After
Initial Start-Up at the back of this section of the manual
for additional corrective procedures.
CHARGING SYSTEM
GENERAL DESCRIPTION
The function of the charging system is to provide electrical
power to the engine ignition system, to the vehicle accessories
and to restore power lost,, from the battery .
The primary component of the system is the generator.
The generator assembly includes the rotor, stator and
recitifier subassemblies and an integral voltage regulator .
When the engine is operating and turning the rotor, an
alternating current flow is induced in the stator assembly
by the electromagnetic field established in the rotor. The
alternating current produced in the stator is changed to
the direct current needed in the vehicle's electrical system
by the rectifier assembly. This is accomplished through
the use of diodes in the rectifier assembly which allow
current flow in one direction only. The output of the generator
is controlled by the voltage regulator. The voltage
regulator does this by varying the strength of the electromagnetic
field established in the rotor assembly.
The generator is connected to the vehicle electrically as
shown in Figure 7-37. The integral regulator is mounted
beneath the rear cover of the generator.
The brown field wire to the generator is used to initially
activate the generator by providing the current needed to
establish the electromagnetic field in the rotor. The
10-ohm resistance, provided by either the generator warning
lamp or the resistance wire with optional gages, is
needed to protect the diodes in the rectifier assembly.
Figure 7-37- Charging Circuit- SI System
ENGINE ELECTRICAL SYSTEM
GENERATOR SIZING AND SELECTION
7-62
The base generator, or Delcotron, in the GM motor home
is rated 63 to 66 amps. Normally, this rating is large
enough for most applications . However, in recent years,
the typical RV owner has purchased and/or added on
optional electrical equipment pushing base charging system
capacity beyond current abilities .
A charging system that has demands beyond system ability
can create problems, as there is not a way to charge
the batteries when the system is always running with an
electrical "short fall." The life expectancy of the charging
system will be greatly reduced when the system is
operating at 100 percent of capacity for extended time.
Also engine compartment configurations and optional
equipment can aggravate the situation due to restricted
air flow and generator overheating .
BATTERY ISOLATOR
NOTE : If GM factory systems are changed, the size of
the main charging wire in the harness must be
changed from a 3mm or 12 AWG wire size to an
8mm or 8 AWG wire size. The larger size charging
wire is mandatory when installing an upgraded
charging system.
The battery isolator is a very important link in the total
electrical system . Typical isolator hook-ups are shown in
Figure 7-37 using broken lines. As shown, the red wire
from the battery to the generator is moved to Terminal
No. 1 of the battery isolator . A replacement wire connects
the generator to Terminal "A" on the battery isolator as
shown .
A typical RV battery isolator wiring schematic is shown in
Figure 7-38. The isolator is equipped with one-way diodes
allowing no reverse current flow back to "A" or between
Terminal No. 1 or Terminal No. 2.
GENERATOR
VOLTMETER
(GAGE PACKAGE
ONLY)
GENERATOR WARNING
LAMP (EXCEPT GAGE PACKAGE)
10 OHMS RESISTANCE
WIRE (RALLY GAGE
ONLY)
NOTE: BROKEN LINES
INDICATE BATTERY
ISOLATOR CONNECTIONS
SECTION 7E
BATTERY GENERATOR BATTERY
1 2
VEHICLE AUXILIARY
ISOLATOR
TO RUN EQUIPMENT:
STEREO, LIGHTS,
REFRIGERATOR, ETC.
Figure 7-38-Typical RV Battery Isolator Wiring
Shown in Figure 7-39 are two typical RV isolator voltmeter
checks that will identify a functional isolator. Voltages are
based on a reasonable state of charge in all batteries (12
volts) .
ENGINE OFF
ENGINE RUNNING
The "Engine Off" voltmeter check depicts a normal
condition showing that the isolator diodes are
functional.
The "Engine Running" voltmeter check depicts a near
equal voltage of 13.5 to 13 .8 volts and indicates a normal
condition . The generator has switched on and current
is passing through both sides of the isolator. You
are not checking the generator amperage capacity,
only the isolator function . If no charge voltage is reaching
one or the other batteries, check for a failed fusible
link or circuit breaker installed in either or both charging
wires.
NOTE: A voltage drop of about 1/2 volt to "1 " and "2"
would be a normal drop through the diodes.
Figure 7-39-Typical RV Isolator Voltmeter Checks
ENGINE ELECTRICAL SYSTEM
7-63
Shown in Figure 7-40 are typical RV battery isolator failure
modes.
Under "Engine Running," the isolator is internally damaged.
Diodes are open or burned out. There is no
charging to either battery in this figure. This failure
mode could also occur singularly to either outer leg of
the isolator.
ENGINE RUNNING
ENGINE OFF
Shown under "Engine Off," the isolator is wired incorrectly
externally or internally. Voltage should not be
supplied to terminal '.'A" with the engine off. Check the
source of the problem by removing the wire from the
"A" terminal . The wire should not have any voltage and
the isolator should not have any voltage either .
Figure 7-40- Typical RV Battery Isolator
Failure Modes
Three prime rules that must be followed for isolators are:
Each leg of the isolator must be sized to equal or
exceed the total generator output. The reason is that
one battery may require all of generator's output while
the other(s) require none . Thus a single leg must be
capable of carrying the maximum generator current
output. Isolators should be purchased oversized if
there is any chance of upgrading the generator at a
later date.
Figure 7-41- Charging Wire Size to Output
2. In the auxiliary battery side, a circuit breaker or fusible
link should be included. A fusible link on the automotive
side will be standard as produced by GM .
3. The size of the charging wire should be chosen using
the chart shown in Figure 7-41 .
CHARGING SYSTEM -1987 TO
CURRENT
SECTION 7E-ENGINE ELECTRICAL SYSTEM
With the start of 1987 production, the CS130 105 AMP
Delcotron generator was provided as standard equipment
on all P-30 motor home chassis . The CS series generator
7-64
is unique in that it requires voltage to both the excitor
terminal and the positive outpost in order to charge.
Solid state isolators are designed to prevent feedback of
current from batteries to the generator. This requires that
the isolator be redesigned to include a fourth terminal
called an excitor terminal . This fourth terminal is connected
to the ignition switch . The ignition switch provides
current when in the "RUN" position to the excitor terminal
on the isolator . Current is allowed to flow from the "E"
terminal via a diode to the "A" terminal providing the necessary
current allowing the generator to charge. Refer to
Figure 7-42 for typical wiring of the solid state isolator and
CS Series Delcotron generator .
BATTERY
1
VEHICLE
GENERATOR
BATTERY
2
AUXILLIARY
TO RUN EQUIPMENT:
STEREO, LIGHTS,
REFRIGERATOR, ETC .
Figure 7-42 - Typical CS Series Delcotron Generator and Solid State Isolator Wiring
GENERATOR
MINIMUM CHARGING WIRE SIZE
FOR WIRE LENGTH IN FEET
RATED 11 FEET 15 FEET 21 FEET 26 FEET
OUTPUT UP TO TO TO TO TO
IN AMPS 10 FEET 14 FEET 20 FEET 25 FEET 30 FEET
Up to 70 amp 10 8 8 6 6
70 to 95 amp 6 6 4 4 4
95 to 120 amp 4 4 4 2 1
120 to 160 amp 4 4 2 2 0
SECTION 7E
CS SERIES GENERATOR AND
ISOLATOR DIAGNOSIS
A preliminary check of a "no charge" condition should be
made to ensure that voltage is provided to both the excitor
("F" terminal) and the positive output post (B+) on the
generator when the ignition is on . If voltage is not present
on either terminal, the generator will not charge. See
Figure 7-43.
1987 TO CURRENT
CS130 DELCOTRON GENERATOR 105 AND
SOLID STATE ISOLATOR
KEY OFF
VOLTS
KEY ON
ENGINE NOT RUNNING
A
KEY ON
ENGINE RUNNING
If isolator voltage checks result in the above readings,
the charging system is functioning normally .
Figure 7-43 - Typical Solid State Isolator Voltage
Checks
ENGINE ELECTRICAL SYSTEM
SOLID STATE ISOLATOR
If voltage is not present at the generator excitor terminar
with the ignition key "ON" check the fuses and wiring .
Repair as necessary . If battery voltage is not present at
the generator output terminal, check the wiring and connections.
Repair as necessary. If the vehicle is equipped
with a solid state battery isolator, check for voltage at the
isolator excitor terminal with the ignition key in the "RUN"
position . If voltage is not present, check the fuse and
wiring . Repair as necessary.
NOTE : When the vehicle is equipped with a solid state
isolator and if the coach battery is discharged
below 9 volts, excessive current will flow from the
chassis battery through the excitor terminal to the
low battery and can cause the excitor fuse to
"blow" causing a "no charge" condition . This occurs
when the key is turned to the "RUN" position
prior to starting the engine.
If voltage is present at the "E" terminal but not on the "A"
terminal, the isolator is defective and will require
replacement.
ELECTROMECHANICAL ISOLATOR
The electromechanical circuit as shown in Figure 7-44
can be used for battery isolation on all 1987 to current
motor chassis equipped with a CS Series generator.
MAINTENANCE AND INSPECTION
No periodic adjustments or maintenance of any kind are
required on the entire generator assembly. However, belt
tension should be checked periodically and adjusted as
required . See Appendix 7-14- Generator Belt Usage on
6.2L Diesel Engines at the back of this section, as well
as the manual Appendix A - Drive Belts and Tension
Specifications located at the back of the manual for additional
information concerning belt tension specifications .
Noise from a generator may be caused by a loose drive
pulley or loose mounting bolts. These parts should be
tightened as required . Other causes of generator noise
can be worn or dirty bearings, defective diode(s) or a
defective stator. Such causes require an overhaul .
SECTION 7E -ENGINE ELECTRICAL SYSTEM
AUXILIARY
BATTERY
NORMALLY
OPEN
MAGNETIC
SWITCH
GM PART NO.
15555675
Figure 7-44 - CS130 Magnetic Switch/Battery Installation Wiring Diagram
IGNITION SYSTEM
GENERAL DESCRIPTION
The ignition circuit consists of the battery, the distributor,
the ignition switch, the spark plugs and the primary and
secondary wiring .
Electrical current to power the ignition system is provided
by the battery during starting and by the charging system
when the engine is operating. This low-voltage current
flows through the ignition switch, the electronic module in
the distributor and the coil in what is called the primary
circuit . In the coil, the low-voltage current is changed to
a high-voltage current each time the primary circuit is
switched off and on by the electronic module. The module
breaks the circuit in response to signals from the magnetic
pickup assembly. These signals are timed with the power
stroke of each cylinder .
The high-voltage current generated in the second part of
the coil, flows to the center terminal of the distributor cap
through the rotor, to each outer terminal of the distributor
cap in rotation . From each distributor cap outer terminal,
the current flows through the wire to the spark plug. At
the spark plug, the current jumps the gap between the
electrodes to ground, producing the spark for ignition . This
high-voltage circuit is referred to as the secondary circuit .
H .E.I. DISTRIBUTOR
The High Energy Ignition (H.E .I.) distributor used on the
5.7L and the Mark IV engines, combines all ignition components
in one unit (Figure 7-45). It is located on top of
the engine block directly behind the carburetor. The external
electrical connections (Figure 7-46) are the ignition
switch feed wire, the tachometer pickup and eight spark
plug leads . The ignition switch feed connector to the distributor
has full battery voltage when the ignition switch is
in the "RUN" and "START" positions . THERE IS NO RESISTOR
WIRE FROM THE IGNITION SWITCH TO THE
DISTRIBUTOR.
The ignition coil is in the distributor cap and connects
through a resistance brush to the rotor. The High Energy
Ignition system is basically identical in operation to conventional
ignition systems except that the module and
pickup coil replace the contact points .
The High Energy Ignition is a magnetic-pulse-triggered,
transistor-controlled, inductive discharge ignition system.
The magnetic pickup assembly located inside the distributor
contains a permanent magnet, a pole piece with internal
teeth, and a pickup coil . When the teeth of the timer
core rotating inside the pole piece line up with the teeth
of the pole piece, an induced voltage in the pickup coil
signals the electronic module to trigger the coil primary
circuit .
IGNITION NORMALLY OPEN RELAY
FUSED GM PART NO. 14089936
NOTE: THE RELAY IDENTIFIED
DELCOTRON MUST BE USED AS THE VOLT-
"P" TERMINAL ' AGE ON THE "P" TERMINAL IS
LESS THAN 12 VOLTS.
CHASSIS BATTERY
DELCOTRON
"I" TERMINAL
DELCOTRON
"B + " POST I
SECTION 7E
COIL
(GM PART NO.
1875894)
CAP
(GM PART NO.
10475118
SEAL
ROTOR
(GM PART NO.
10470600
VACUUM
UNIT
CONNECTOR
* NOTE: LATER PRODUCTION ROTOR IS
OFF-WHITE IN COLOR -WITH
HIGHER DIELECTRIC STRENGTH
Figure 7-45-H.E.I . Distributor-Exploded View
The primary current decreases and a high voltage is induced
in the ignition coil secondary winding which is directed
through the rotor and secondary leads to fire the
spark plugs. The capacitor in the distributor is for radio
noise suppression.
The magnetic pickup assembly (Figure 7-47) is mounted
over the main bearing on the distributor housing and is
made to rotate by the vacuum control unit, thus providing
vacuum advance. Thetimer core is made to rotate about
the shaft by conventional advance weights, thus providing
centrifugal advance.
The module automatically controls the dwell period,
stretching it with increasing engine speed. The H.E .I . system
also features a longer spark duration, made possible
by the higher amount of energy stored in the coil primary
winding. This is desirable for firing lean mixtures.
ENGINE ELECTRICAL SYSTEM
7-67
CONNECTOR B+ TERMINAL
BAT. TERMINAL
(CONNECTED TO
IGNITION SWITCH)
TACH I
CONNECT
TACHOMETER
FROM THIS
TERMINAL TERMINAL
TO GROUND.
NOTE: HOLD DOWN BRACKET POSITIONED ON
THIS FLANGE SECURES DISTRIBUTOR TO
ENGINE BLOCK.
(SOME TACHOMETERS MUST CONNECT FROM
THIS TERMINAL TO ENERGIZE POSITIVE [+1.
CONSULT TACHOMETER MANUFACTURER.)
NOTE: CHISEL MARK ON SOME PRODUCTION
ENGINE DISTRIBUTOR FLANGES TO
MANIFOLD SHOWS TIMING AS PRODUCED
BY PLANT.
Figure 7-46- H.E.I . Distributor Assembly
Electrical Connections
SECONDARY WIRING
The spark plug wire used with the H.E .I . system is a
carbon-impregnated cord conductor encased in an
8mm diameter silicone rubber jacket. The silicone wiring
will withstand very high temperatures and also provides
an excellent insulator for the higher voltage of the H.E .I .
system . The silicone spark plug boots form a tight seal
on the plug .
SPARK PLUGS
Resistor-type, tapered-seat spark plugs with a 14mm
thread diameter are used on the 5.71- and Mark IV gasoline
engines. (See figure 7-48.) A gasket is not used on these
tapered-seat plugs. The recommended torque specification
for installing the plugs in these engines is 17-27 ft .
lbs.
Normal or average service is assumed to be a mixture of
idling, slow-speed and high-speed operation with some
of each making up the daily total driving. Occasional or
intermittent high-speed driving is essential to good spark
plug performance as it provides increased and sustained
combustion heat that burns away any excess deposits of
carbon or oxide that may have accumulated from frequent
idling or continual stop-and-go or slow-speed driving.
SECTION 7E ENGINE ELECTRICAL SYSTEM
DISTRIBUTOR
BASE
VACUUM
CONTROL
UNIT
ELECTRONIC MODULE - NON FUEL INJECTED ENGINES
(GM PART NO. 1875990)
FUEL INJECTED ENGINES 350-454
(GM PART NO. 10496048)
CAPACITOR
(SOME MODELS)
POLE PIECE
(GM PART NO. 1875981) now FI
(GM PART NO. 10495801) with FI
SHAFT
Figure 7-47- H.E.I. Magnetic Pickup Assembly
ENGINE
350 CID
454 CID
1983-1984
R45T
R44T
INSTALLATION
TORQUE
17-27 FT. LB.
GAP .045
AC PART NO.
1985-1989
CR43TS
R44T
GAP
1990-1994
*R43TS
Figure 7-48- Spark Plug
Spark plugs are protected by an insulating nipple made
of special heat-resistant material which covers the spark
plug terminal and extends downward over a portion of the
plug insulator . These nipples prevent flash-over with resultant
missing of engine, even though a film is allowed
to accumulate on the exposed portion of plug porcelains.
Do not mistake corona discharge for flash-over or a
shorted insulator . Corona is a steady blue light appearing
around an insulator, just above the shell crimp. It is the
visible evidence of high-tension field and has no effect on
ignition performance. Usually it can be detected only in
darkness.
This discharge may repel dust particles, leaving a clean
ring on the insulator just above the shell . This ring is
sometimes mistakenly regarded as evidence that combustion
gases have blown out between the shell and
insulator .
SECTION 7E
If it should become necessary to remove and replace the
spark plugs, do not substitute a spark plug having a different
heat range in order to compensate for a performance
complaint . A spark plug of the proper heat range
and one that is properly gapped will not cause a driveability
problem. If spark plugs are installed that have a
higher heat range than called for, the valves can become
"tuliped" or the pistons can become pitted, eroded and
burned through . On the other hand, if spark plugs with a
lower than called for heat range are installed, plug fouling
and bad emissions will usually result.
NOTE: Generally, spark plugs containing the suffix TS or
CTS can be used interchangeably. (See Figure
7-48.) However, during the 1986 model year, AC
Spark Plug changed the center electrodes in their
spark plugs to copper. For these plugs, the letter
C may be removed from the identification number
on the jacket . EXAMPLE: A spark plug with a
code identification of Re43TS or R43CTS would
be changed to *R43TS.
IGNITION TIMING
To assure optimum engine performance, the ignition must
be properly timed. This means that the spark plug must
fire at precisely the instant when the fuel mixture is correct
and cylinder compression is highest .
Set the ignition timing by following these instructions :
1 . Refer to the Vehicle Emission Control Information Label
located on the radiator support panel. Follow all
instructions on the label. .
2. With ignition off, connect the pickup lead of the timing
light to the number 1 spark plug wire (engines with the
timing pointer mounted over the upper side of the damper),
or to the number 5 or 8 spark plug wire (engines
with the timing pointer mounted at the lower left side
of the damper). Use a jumper lead between the wire
and plug or an inductive-type pickup. DO NOT pierce
the wire or attempt to insert a wire between the boot
and the wire. Connect the timing light power leads
according to manufacturer's instructions .
3. Disconnect and plug the vacuum line at the distributor .
4. Start the engine and aim the timing light at the timing .
mark. (See Figure 7-49 .) The line on the balancer or
pulley will line up at the timing mark. If a change is
necessary, loosen the distributor hold-down clamp bolt
at the base of the distributor. While observing the mark
with the timing light, slightly rotate the distributor until
the line indicates the correct timing . Tighten the holddown
bolt and recheck the timing .
On a motor home chassis with the engine having the
timing pointer mounted at the lower left side of the
damper, the timing light must be aimed up from beneath
the vehicle . This procedure require,$ two people,
one to observe the mark with the timing light while the
second person makes any required adjustments at the
distributor.
ENGINE ELECTRICAL SYSTEM
7-69
WATER
PUMP
TIMING POINTER -
ALTERNATE POSITION
(LOWER SIDE)
Note: View with
timing light
from
underside
of vehicle . TIMING POINTER
(UPPER SIDE)
Note: View with timing light
from top of engine.
Figure 7-49-Timing Mark- Typical
5 . Turn off the engine and remove the timing light. Reconnect
the number 1 spark plug wire, if removed .
MAINTENANCE AND INSPECTION
H.E.I. DISTRIBUTOR
No periodic lubrication is required . Engine oil lubricates
the lower bushing and an oil-filled reservoir provides lubrication
for the upper bushing.
H.E.I. TEST PROCEDURE
If there appears to be a problem with the ignition system,
the following procedure can be used as a quick-check in
determining the cause. More detailed procedures are
given in the appropriate shop manual .
General Test
1 . Remove a spark plug wire from each spark plug one
at a time and check for spark using an H .E.I . Test Spark
Plug ST125 (GM Part No. 5613602) or equivalent. If
spark is present, the H.E.I. system is O.K.
NOTE: Using the Test Spark Plug to check for spark
instead of allowing the spark to jump to ground
from the disconnected wire can help to avoid pos
sible damage to the module. A Test Spark Plug
should be available at a local auto parts store.
2. Connect a test light between the distributor TACH terminal
and ground.
3. Turn on the ignition switch.
" If the light does not glow, check for power at the
distributor BAT terminal . If there is no power at the
BAT terminal, the problem is in the circuit wiring or
the ignition switch. Repair as required . If there is
power at the BAT terminal, and no power at the
TACH terminal, the ignition coil primary winding is
open . Replace the coil.
" If the light glows, crank the engine. The light should
glow intermittently, indicating that the module and
pickup coil are working. Remove the distributor cap
and check for spark at the center terminal of the cap
using the H.E.I. Test Spark Plug and a jumper wire.
If there is spark, the rotor is not functioning and
should be replaced. If there is no spark, the coil is
not functioning and should be replaced .
If the light glows steadily while the engine is being
cranked, perform the module test.
Module Test
SECTION 7E-ENGINE ELECTRICAL SYSTEM
1 . Remove the distributor cap and connect the H .E.I . Test
Spark Plug to the center terminal with a jumper wire.
2. Remove the pickup coil connector from the module
and turn the ignition switch on.
3. Touch one end of another jumper wire to the positive
terminal of the battery and the other end to the small
terminal of the module momentarily. As the jumper wire
is removed from the module terminal, if there is:
" a spark- the pickup coil is not functioning properly
and may need to be replaced .
" no spark - the module is not functioning properly
and may need to be replaced .
CHECKING H.E.I. SYSTEM CONNECTIONS
If a component appears to be inoperative, the condition
may actually be due to poor connections. This is especially
true of low-voltage circuits, such as the pickup coil to
module connections in the H.E.I . system.
Before any component or assembly is considered faulty
and replaced, its terminal(s) should be cleaned, the connector-
to-terminal fit tightened and the wire-to-terminal
connection checked and resoldered if necessary.
The following procedure covers one example involving
H .E.I. low-voltage circuits where good connections are
essential . Refer to Figure 7-50.
1 . Remove the module and clean the terminals with
emery cloth or a wire brush to remove any oxide film.
2. Remove the connector body (if so equipped) from the
pickup coil leads. Carefully inspect the terminal-to-wire
connections (green and white leads) and recrimp if
7-70
PUT VASELINE ON
BLADE TERMINALS
CONNECTOR
REMOVED
WHITE WIRE
(SOLDER CLIP
TO WIRE)
(SQUEEZE COIL
TERMINALS)
NOTE: REFER TO GM SERVICE
BULLETIN NO. 78-1-59
DATED OCTOBER, 1978
Figure 7-50- Module Connections
loose. Reflow the existing solder, and add solder if
necessary to assure good connections. Avoid excess
solder . Use a small iron or gun . Do not allow heat to
damage the insulation or solder to run under the terminal.
Squeeze the side rails of the terminals with
needle-nose pliers to assure a tight fit on the module
terminals .
3. Apply a thin coating of petroleum jelly (i .e., Vaseline)
on all module terminals to reduce future oxidation .
Make sure a small amount of silicone heat transfer
grease (AC-Delco D-1920 or equivalent) is present on
the module base. Apply the grease if necessary.
4. Reinstall the module on the H.E.I. base and reconnect
the leads making sure all terminals are seated with
good metal-to-metal contact .
SPARK PLUG WIRES
Use care when removing spark plug wire boots from spark
plugs. Twist the boot 1/2 turn before removing, and pull
on the boot only to remove the wire. Borroughs Tool No.
BT-7901 B or-equivalent will make the removal of the spark
plug wires easier. (See Figure 7-51 .)
It is extremely important when replacing plug wires to
route the wires correctly and through the proper retainers .
Failure to route the wires properly can lead to radio ignition
noise and crossfiring of the plugs, or shorting of the leads
to ground.
SECTION 7E
BORROUGHS TOOL NO .
BT-7901 B HEAT TREATED
SPRING STEEL CONSTRUCTION
FOR LONG LIFE
Phone No. 1-800-253-0138
Figure 7-51 -Spark Plug Boot Puller
Figure 52-Spark Plug Shield for 7.41-
Cyl . 1 thru 6 & 8 10089660 2-518 inch
Cyl . 7 10089661 1-7/8 inch
SPARK PLUGS
Worn or dirty plugs may give satisfactory operation at
idling speed, but under operating conditions they frequently
fail .
Faulty plugs are indicated in a number of ways: poor fuel
economy, power loss, loss of speed, hard starting and
general poor engine performance.
Spark plug failure, in addition to normal wear, may be due
to carbon fouled plugs, excessive gap or broken insulator .
(See Figure 7-48 .)
Fouled plugs may be indicated by checking for black car-
ENGINE ELECTRICAL SYSTEM
7-71
bon deposits . The black deposits are usually the result of
slow-speed driving and short runs where sufficient engine
operating temperature is seldom reached. Worn pistons,
rings, faulty ignition, over-rich carburetion and spark plugs
which are too cold will also result in carbon deposits.
Excessive gap wear, on plugs of low mileage, usually
indicates the engine is operating at high speeds or with
loads that are consistently greater than normal or that a
plug which is too hot is being used . In addition, electrode
wear may be the result of plug overheating, caused by
combustion gases leaking past the threads, due to insufficient
torquing of the spark plug. Excessively lean carburetion
will also result in excessive electrode wear.
Broken insulators are usually the result of improper installation
or carelessness when regapping the plug. Broken
upper insulators usually result from a poor-fitting
wrench or an outside blow. The cracked insulator may not
make itself evident immediately, but will as soon as oil or
moisture penetrates the fracture . The fracture is usually
just below the crimped part of the shell and may not be
visible.
Broken lower insulators usually result from carelessness
when regapping and generally are visible. In rare instances,
this type of break may result from the plug operating
too "hot," encountered in sustained periods of
high-speed operation or under extremely heavy loads.
When regapping a spark plug, to avoid lower insulator
breakage, always make the gap adjustment by bending
the ground (side) electrode . Spark plugs with broken insulators
should always be replaced .
6:21 DIESEL GLOW PLUG
ELECTRICAL SYSTEM
GENERAL DESCRIPTION
In the diesel engine, air alone is compressed in the cylinder;
then after the air has been compressed, a charge
of fuel is sprayed into the cylinder and ignition occurs due
to the heat of compression . Eight glow plugs are used to
preheat the chamber as an aid to starting.
The glow plugs are heaters that turn on when the ignition
key is turned to the run position prior to starting the engine.
They remain pulsing a short time after starting, then automatically
turn off.
SYSTEM COMPONENTS
The 6 .2-liter diesel glow plug control system consists of
a thermal controller, glow plug relay, 6-volt glow plugs and
a "glow plugs" lamp. (See Figure 7-53) Other components
which have no function in controlling glow plug operation
but are part of the electrical system, start-and-run
"operations are : fuel solenoid, fast idle and cold advance
solenoids, cold advance temperature switch and the TCC,
EGR (if equipped) and EPR solenoids. The electrical operation
and diagnosis of the fuel solenoid, fast idle and
cold advance solenoid and the cold advance temperature
switch will be covered briefly here .
Plug Wire Set
85-86 H4D 12043750
85-89 H5D 12072181
90-93 H5D 12074045
SECTION 7E
GLOW PLUG INHIBIT
TEMP SWITCH
GM PART NO. 15599010
GLOW PLUG
CONTROLLER
GM PART NO. 12040822
Figure 7-53 - Electronic Glow Plug Control System 1985 and Forward
Controller
The thermal controller is mounted in the water passage
at the rear of the engine.
Thermostatic, elements within the controller are designed
to open or close the ground circuit to the glow plug relay
as necessary to control the preheat and afterglow cycles
of glow plug operation .
Glow Plug Relay
The glow plug relay provides current to the glow plugs.
The relay is pulsed on and off by the thermal controller.
NOTE: Do not bypass the glow plug relay. This relay is
automatically controlled. Any attempt to bypass
the relay with a jumper wire or rewire for manual
control, may result in glow plug failure .
Glow Plugs
The glow plugs used in this system are 6-volt plugs which
are operated at electrical system voltage (12 volts) . The
plugs are a "fast start" design capable of reaching 1,800°F
in 7.5 to 9 seconds when the engine temperature is 0°F.
They are not designed to burn continuously and are
pulsed on and off as needed, by the thermal controller.
ENGINE ELECTRICAL SYSTEM
7-72
"Glow Plugs" Lamp
The "glow plugs" lamp is mounted in the instrument cluster.
The lamp is wired across the glow plugs and is illuminated
whenever the glow plugs are heated.
Fuel Solenoid
The fuel solenoid is activated whenever the ignition switch
is on. The solenoid is located in the fuel injection pump
housing cover.
Cold Advance Solenoid
The cold advance solenoid, also located in the injection
pump cover, is controlled by a cold advance temperature
switch which activates this solenoid and the fast idle solenoid
at a specified minimum temperature. The switch
should be closed below 90°F and open above 122°F.
Instrumentation
Vehicles with the diesel engine. have special instrumentation
indicators to permit the operator to properly apply
the starting procedure . A "glow plugs" light on the instrument
panel provides this information on the engine starting
conditions.
FAST IDLE & COLD ADVANCE
TEMP. SW. OPENS AT 95OF
10 OHMS
W/vAvUESI
SECTION 7E -ENGINE ELECTRICAL SYSTEM
Figure 7-54 - Diesel Glow Plug Wiring Diagram 198285
Also these vehicles have a "water-in-fuel" lamp and "low
engine coolant" lamp.
Modifications Required for Diesel Starting
BATTERY - The diesel engine uses dual batteries to
provide the extra power required to operate the glow plugs
and the larger starter used on this engine .
A standard generator supplies charging current to both
batteries at the same time . There are no switches or relays
in the charging circuit.
STARTER -The starter is larger and designed to crank
the engine to at least the 100 RPM required for starting .
Circuit Operation - Cold Start (See Figure
7-54)
With the ignition switch in "RUN,'' the following events
take place simultaneously :
1 . The fuel solenoid is energized and opens the fuel metering
valve. The fuel heater is powered, provided the
temperature is low enough to require heating of the
7-73
fuel .
150
NOTE : TERMINAL
"5", BLK . GRD.
SPLICES INTO
TERMINAL "W',
BLK, AT SPLICE
150. THEY THEN
GRD. A T ENG .
NOTE : THE T .C .C . SOL . SWITC H
WILL OPEN AT W.O .T . ONLY
WHEN THE SWITCH IS NOT
ATTACHED TO THE INJ . PUMP
2. Battery voltage is applied to the fast idle solenoid and
cold advance solenoid through the fast idle/cold advance
temperature switch (when closed) .
3. Battery current flows through the thermal controller circuits
and through the glow plug relay coil to ground.
4. The glow plug lamp, which is wired across the glow
plugs, comes on whenever the glow plugs are
powered .
5. The thermal controller starts the glow plug's heating
cycle.
Initially, the glow plugs are activated continuously for a
period of 7.5 to 9 seconds at 0°F (Figure 7-55). The glow
plugs then begin to pulse on and off at arate determined
by the thermal characteristics of the controller.The initial
current brings the glow plug preheat chamber up to the
temperature required forcold starting.The pulsecycle(on
and off)acts to maintain chambertemperature to provide
stable engine warm-up. As the engine warmsup, the therSECTION
7E -ENGINE ELECTRICAL SYSTEM
mal controller turns off all current to the relay, deenergizing
the glow plugs completely. The controller is capable
of varying glow plug operation as required (up to one
minute) when the engine is started warm, and little or no
heating is necessary.
Controller failure, as in the case of prolonged preheat
(more than 9 seconds), would cause a circuit breaker in
the controller to open, cutting off glow plug operation
completely.
GLOW PLUG
TEMPERATURE
"FAST START" SYSTEM
2,000 °F
7.5 TO 9 SEC.
ENGINE READY
TO CRANK
PRE-CHAMBER
WARM UP TIME
Figure 7-55 - Glow Plug Control
MAINTENANCE AND INSPECTION
No routine service is required for the diesel glow plug
electrical system . However, should there be a problem
with the system, it is wise to first inspect the system to
ensure that all connectors are installed properly and that
all connections are clean and tight. The glow plugs can
be checked for continuity with the procedure in this section.
If the inspection and checks do not reveal the problem,
refer to the shop manual for the diagnosis procedure .
GLOW PLUG TEST
This test can be performed with the plugs either installed
or removed from the engine. If the plugs are installed, the
engine should be off and the feed wire disconnected from
each plug .
Using an ohmmeter, adjusted to a low-range scale,
check for continuity between the terminal and body of
each plug as shown in Figure 7-56. The ohmmeter reading
should be approximately 0.5 ohm. If the reading is infinity,
the glow plug coil is burned out or faulty and the
plug should be replaced.
Figure 7-56 - Glow Plug Test
The following information is provided as an aid to the
motor home owner in understanding battery size and
cranking capacity in relation to temperature.
The chart shown in Figure A7-10-1 explains why a battery
of sufficient electrical size is essential if satisfactory cranking
of the engine is to be achieved at low temperatures .
At temperatures below zero, the capacity of the battery
at full charge is about 30 percent of rated capacity at 80°F.
At the same time, the load imposed on the battery by the
engine is about 3-1/2 times the normal cranking load at
80°F. In effect, at lower temperatures the battery would
seem "smaller" while the engine would appear to be
"larger," as depicted in the figure .
The charts below (Figure A7-10-2) provide an example of
the "shrinking" battery in terms of Cold Cranking Amps
(CCA) in relation to temperature.
Just as low winter temperatures can create cold-start
cranking problems due to the electrical size and cranking
capacity of a battery, the majority of winter engine failures
are skuff and bearing seizures that occur upon initial startup.
The reason for these problems is oil starvation from
drain-off and the fact that the oil is too thick to pump quickly
to the bearing surfaces.
APPENDIX 7-10
BATTERY SIZE AND CRANKING
vs. TEMPERATURE
100% FULL-CHARGED BATTERY
65% CHARGED BATTERY - GREEN EYE VISABLE
Figure A7-10-2-Cold Cranking Amps vs. Temperature
7-75
Figure A7-10-1- Battery Cranking vs. Temperature
For best fuel economy and cold starting protection to engine
surfaces, consider the range of temperature your
vehicle will be operated in during the next oil change.
Then, select the recommended oil viscosity from the applicable
chart shown in Figure A7-10-3.
BASE BATTERY HD BATTERY
405 CCA 650 CCA
80 DEGREES = 100% 880 CCA 1413 CCA
32 DEGREES = 68% 598 CCA 960 CCA
0 DEGREES = 46% 405 CCA 650 CCA
-20 DEGREES = 30% 264 CCA 423 CCA
BASE BATTERY HD BATTERY
' 405 CCA 650 CCA
80 DEGREES = 100% 572 CCA 918 CCA
32 DEGREES = 68% 389 CCA 624 CCA
0 DEGREES = 46% 263 CCA 422 CCA
-20 DEGREES = 30% 171 CCA 275 CCA
APPENDIX 7"f0
BATTERY SIZE AND CRANKING
vs. TEMPERATURE (Cont'd)
of
+100
Hot Hot
Weather Weather
+60
+40
+32
+20
+10
0
-20
SAE 30
SAE 20W-20
---® SAE 15W-40
SAE IOW-30
PREFERRED
Cold Cold
Weather Weather
GASOLINE ENGINES DIESEL ENGINES
Figure A7-10-3-Gasoline and Diesel Engine Oil Viscosity Charts
NOTE: THE GM MAINTENANCE SCHEDULE RECOMMENDS
INSPECTION OF ALL ENGINE
DRIVE BELTS AT EACH OIL CHANGE. DRIVE
BELTS SHOULD BE INSPECTED FOR
CRACKS, FRAYING AND WEAR . DRIVE
BELTS SHOULD BE ADJUSTED OR REPLACED
AS NEEDED. SEE APPENDIX A -
DRIVE BELTS AND TENSION SPECIFICATIONS
AT THE BACK OF THIS MANUAL FOR
ADDITIONAL INFORMATION .
APPENDIX 7-10
BATTERY SIZE AND CRANKING
vs. TEMPERATURE (Cont'd)
NOTE- The following charts are provided to aid service
personnel and the motor home owner for proper
engine electrical diagnosis.
SLOW CRANKING, SOLENOID CLICKS OR CHATTERS
REPAIR GROUND
CABLE AND
CONNECTIONS
CHECK: BATTERY FOR GREEN INDICATOR.
VISUAL CONDITION OF BATTERY CABLES AND CONNECTIONS.
IF BATTERY NEEDS CHARGING, MAKE GENERATOR AND
BATTERY DRAIN CHECK, CHARGE BATTERY AND RECHECK
CRANKING . IF TROUBLE HAS NOT BEEN FOUND, PROCEED.
REMOVE BATTERY LEAD FROM DISTRIBUTOR ON H.E .I . MAKE ALL
VOLTMETER READINGS WITH KEY IN START POSITION .
MEASURE CRANKING VOLTAGE AT BATTERY TERMINAL POSTS.
9.6 VOLTS OR MORE
MEASURE VOLTAGE FROM BATTERY
NEGATIVE TERMINAL TO ENGINE
BLOCK. (POS. LEAD ON BLOCK.)
MEASURE VOLTAGE
AT SOLENOID "B"
TERMINAL, CLEAN
AND TIGHTEN
CONNECTIONS AT
STARTER
CLEAN AND
TIGHTEN
POSITIVE CABLE
CONNECTIONS. IF
O.K ., REPLACE
CABLE.
LESS THAN 9.6 VOLTS
CHECK BATTERY CONDITION
AND CAPACITY
NOTE: THIS PROCEDURE IS DESIGNED FOR USE ON ENGINES AND BATTERIES AT ROOM OR NORMAL
OPERATING TEMPERATURES. ITALSO ASSUMES THERE ARE NO ENGINE DEFECTS WHICH WOULD
CAUSE CRANKING PROBLEMS. TO USE IT UNDER OTHER CONDITIONS MIGHT RESULT IN
MISDIAGNOSIS.
Figure A7-10-4- Slow Cranking - Diagnosis Chart '
7-77
BATTERY SIZE AND CRANKING
vs. TEMPERATURE (Cont'd)
GREEN EYE
SHOWING
TEST BATTERY: IF
O.K ., REPAIR
STARTER
5 VOLT
OR MORE
CLEAN AND
TIGHTEN
GROUND CABLE
CONN. AND/OR
REPLACE CABLE
CLEAN AND
TIGHTEN POS.
BATTERY CABLE
TERMINALS
AND/OR REPLACE
CABLE.
NO CRANKING, NO SOUND FROM SOLENOID
LIGHTS DIM OR GO OUT
CHECK BATTERY STATE-OF-CHARGE
CHECK
CRANKING
VOLTAGE AT
BATTERY
POSTS.
LESS THAN 9.6 VOLTS
9.6 VOLTS OR MORE
LESS THAN 9 VOLTS
9 VOLTS OR MORE
EYE DARK OPERATE O.K . DON'T OPERATE
CHECKVOLTAGE
FROM ENGINE
BLOCK TO BATT.
NEG. POST. KEY
IN START
POSITION, (POS.
LEAD ON BLOCK).
LESS THAN
.5 VOLT
f
CHECK
CRANKING
VOLTAGE AT
STARTER "B"
TERMINAL
CHECK
FUSEABLE LINK
AND BULKHEAD
CONNECTOR.
APPENDIX 7-10
TURN HEADLIGHTS AND DOME LIGHT ON.
TURN KEY TO START
Figure A7-10-5-No Cranking -Diagnosis Chart
CARS WITHOUT
NEU. ST. SW.
CHECK CONNECTIONS AND
VOLTAGE AT SOLENOID "B"
TERM.
REPAIR STARTER
7-78
L
CARS WITH
NEU. ST. SW.
CHECK VOLTAGE AT EACH NEUTRAL
START SWITCH TERMINAL (AUTO.
TRANS. IN PARK, MAN. TRANS.
CLUTCH DEPRESSED, KEY IN
START) .
7 VOLTS
OR MORE
REPAIR PURPLE
WIRE FROM
IGNITION SWITCH
LIGHTS STAY BRIGHT
TURN ON RADIO, HEATER AND
TURN SIGNALS
CHECK
BULKHEAD
CONNECTOR,
FUSEABLE LINE
AND IGNITION
SWITCH
CONNECTIONS.
LESS THAN
7 VOLTS ON
ONE TERM.
CHECK
NEUTRAL
START SWITCH
ADJUSTMENT
AND
CONNECTOR; IF
O.K ., REPLACE
SWITCH
WITH KEY IN START, CHECK VOLTAGE AT
IGNITION SWITCH SOLENOID TERM.
LESS THAN
7 VOLTS
REPLACE
IGNITION
SWITCH
ADD-ON (AUXILIARY)
ELECTRICAL EQUIPMENT
INSTALLATIONS
The following information has been extracted from a
Chevrolet Dealer Service Technical Bulletin relating to
add-on (auxiliary) electrical equipment installations for vehicles
with side terminal batteries .
Reference: Chevrolet Dealer Service Technical Bulletin
No. 85-17 (December, 1984)
The use of electronics on today's vehicles require that
both power and ground connections for add-on (auxiliary)
electrical equipment (mobile radios, light bars, etc .) be
made at the battery .
The Side Terminal Adaptor Package (GM Part No.
1846855) when combined with the longer battery bolt (GM
Part No. 12004188) and spacer (GM Part No. 12004189)
will provide and maintain corrosion resistance and the
electrical integrity designed into the Delco side terminal
battery . (See Figure A7-11-1 .) GM recommends that all
service personnel and motor home owners involved in
add-on (auxiliary) electrical equipment installations perform
the following procedures.
The vehicle battery should -be located and positioned to
ADD-ON (AUXILIARY) EQUIPMENT CABLE(S)
TERMINAL COVER'
APPENDIX 7- 11
VEHICLE BATTERY CABLE
LONG BATTERY
TERMINAL BOLT -
GM PART NO. 12004188
Figure A7-11-1-Add-On Electrical Equipment-Typical Installation
7-79
make use of the existing battery cables. If the battery
requires relocation and longer cables are required, a proportionately
larger gauge wire must be used.
If in relocating the battery, the negative ground cable is
attached to the frame rail, a cable of similar gauge must
be provided between the frame rail and the engine. This
is required due to the heavy electrical loads imposed by
the starting circuit .
To ensure proper operation of the battery cables, the following
chart on length, gauge and materials must be adhered
to :
Figure A7-11-2- Add-On Electrical Equipment-
Wire Gauge and Materials
Specifications
ADAPTER TERMINAL*
CONTACT SPACER
GM PART NO. 12004189
VEHICLE BATTERY
'PART OF TERMINAL ADAPTER
PACKAGE, GM PART NO. 1846855.
ALSO SOLD SEPARATELY BY
DELCO (PART NO. 7450 - 10 TO
A BOX)
CABLE COMBINED LENGTH OF POSITIVE AND
GAUGE NEGATIVE CABLE IN INCHES
COPPER COPPER CLAD ALUMINUM
4 66 52
2 , 107 67
0 170 111
First item to check when hot start (hot soak) is the
ground cable - LH frame rail to LH cylinder head.
Poor ground give high resistance when hot . Remove
bolts and clean - be sure the star washer is used to
insure good ground.
The following information has been extracted from three
GM Service Bulletins relating to "hot start" problems. The
information begins with a discussion of the simple basics
of loose connections, proceeds to the addition of heat
shields and finally to adding a magnetic switch. Problem
conditions and corrective procedures are described .
Reference: Chevrolet Dealer Service Technical Bulletin
No. 90-332-8A (August, 1990)
All Gasoline Engine Models
APPENDIX 7"12
"HOT START" PROBLEM
CONDITIONS
CONDITION : Starter solenoid does not engage in the
ring gear during hot restart . Clicking sound is heard
while trying to start the vehicle .
CAUSE: The starter solenoid engagement force is not
strong enough to withstand the high temperature environment
on some recreational vehicles .
CORRECTION : First, check the usual causes for a
"clicking" solenoid . These causes include a discharged
or defective battery, defective switches, excessive
Figure A7-12-1- "Hot Start" Problems - Starter Solenoid
7-80
control circuit/connection resistance, or a defective
solenoid.
If no troubles are found, a new starter solenoid
package, PIN 10457024, is available to repair the vehicle.
This package consists of a solenoid, lever and
plunger assembly lever pin, and retaining ring. Make
sure all Parts in the package are used.
The vehicle battery should be located and positioned to
make use of the existing battery cables. If the battery
requires relocation and longer cables are needed, larger
gauge cables must be used to ensure proper voltage
requirements.
To ensure proper operation of the battery cables, the following
chart on length, gauge and materials must be
strictly adhered to.
Figure A7-12-2-Battery Cable Gauge Specifications
CABLE COMBINED LENGTH OF POSITIVE AND
GAUGE ' NEGATIVE CABLE IN INCHES
COPPER COPPER CLAD ALUMINUM
4 66 52
2 107 67
0 170 111
APPENDIX 7-12
"NOT START" PROBLEM
CONDITIONS (Cont1d)
Reference:Chevrolet Dealer Service Technical Bulletin
No. 78-T-28 (April, 1978)
P-Series Motor Homes with Mark IV Engines
The generic term "hot start" is applied loosely to an array
of causes which can lead to an inability to crank. Typical
"hot start" symptoms involve failure to crank after a 20-
minute "hot soak" period with the engine off. Restarts are
obtained by waiting for the engine compartment cool
down, or in some cases, by energizing the starter solenoid
directly with a screwdriver across the "S" and "B+"
terminals .
High ambient and/or underhood temperatures can lead to
component overheating . The two starting system components,
most vulnerable to adverse thermal effects, are
the battery and the starter motor solenoid as follows :
1 . Batteries subjected to long-term storage or operating
conditions which do not keep the battery adequately
charged may be marginal because of sulfation . When
operated in high ambients, electrolyte temperatures
may be excessive . During engine-off hot soak periods,
marginal batteries adjacent to radiators may approach
the boiling point of the electrolyte, (about 230°F) depending
on state of discharge .
2. The starter motor solenoid, in close proximity to the
exhaust pipe, is subject to radiant heating which ultimately
increases coil resistance. The resistance increase,
decreases current flow to the point where the
coil cannot be energized with the available applied
voltage .
NOTE: Some motor home body builders install batteries
in a tray near the radiator, while others use a
sliding shelf away from engine temperatures . The
trade-off, however, is longer battery cables and
a higher voltage drop . Battery thermal guards or
heat shields, reflective paints, and/or battery relocation
are appropriate where evidence indicates
battery thermal problems.
In some cases, the battery voltage available for solenoid
operation is adequate when the coil is relatively cool, but
insufficient when the coil is hot. Typically, the voltage drop
across the ignition switch, neutral start switch circuit, to
the solenoid, should not exceed 2 volts. This, normally,
would allow approximately 8 volts for solenoid operation.
Unfortunately, the ignition/start circuit voltage drop can
exceed 4 volts due to switch contact resistance, wire
lengths, etc . Since the solenoid requires a minimum of 7
volts for positive operation, a marginal or "no start" situation
can occur.
On "hot start" complaint vehicles that exhibit symptoms
related to inoperative solenoids, the use of magnetic
switch, GM Part No. 001486 or No. 1115616 (or equivalent)
is recommended. It is, in effect, a high-current relay
whose contacts are connected across the solenoid "S"
and "B+" terminals . (See Figure A7-12-3.) The coil of
the magnetic switch is connected in series with the ignition/
neutral start switch circuit . Maximum available voltage
is, therefore, applied to the solenoid, since the voltage
drop in the magnetic switch contact circuit is virtually zero.
i
II~,I1;II1~ "
MITI 1110
WINDING
SOLENOID
PLUNGER
SHIFT
LEVER
CLUTCH
HOLD IN
CRANKING
MOTOR
MAGNETIC SWITCH
BATTERY
G M '
PART NO:
001486
OR GM
ART NO.
1115616
IGNITION
SWITCH
Figure A7-12-3 - Magnetic Switch/Starter Schematic
7-81
8.
9.
APPENDIX 7-72
"HOT START" PROBLEM
CONDITIONS (Cont1d)
Installation and connection of the magnetic switch can be
accomplished as follows :
1 . Drill two holes in the oil dipstick tube bracket . Use
holes in the magnetic switch mount as a template for
hole location. Removal of bracket will facilitate drilling.
(See Figure A7-12-4 .)
2. Mount the magnetic switch to the dipstick (tube)
bracket using locking fasteners.
3. Unwrap harness tape, from engine harness wire bundle
(approximately one foot) in area adjacent to magnetic
switch .
4. Locate the No. 12 AWG wire with purple insulation.
This wire connects the neutral start switch to the
starter motor solenoid "S" terminal .
5. Cut the wire at a point which will allow connection of
the severed ends to the magnetic switch.
6. Identify the cut end of the wire which connects to the
"S" terminal of the starter motor solenoid. Terminate
this wire with an appropriate lug for connection to one
of the "large" studs on the magnetic switch.
7. Terminate the other end of the cut wire with an appropriate
lug for connection to one of the "small"
studs on the magnetic switch.
If normal diagnosis of battery or wiring does not disclose
any out-of-line conditions, the problem may be caused by
the solenoid return spring . This problem can be corrected
by installing a new shorter return spring, GM Part No.
1978281 or equivalent. Or, install a new high-heat re
Connect the remaining "small" stud on the magnetic sistant solenoid, GM Part No., 1114458 (brown color) or
switch to a secure chassis ground. equivalent, which incorporates the shorter return spring .
Disconnect all of the wires from the "B+" junction
block and attach them to the remaining "large" stud
on the magnetic switch .
Figure A7-12-4 - Magnetic Switch Mounting and Connection
7-82
10. Run a functional/electric check to assure system
operation .
In field situations where it is impractical to install a magnetic
switch, use of reflective paint to reduce heat absorption
is an alternative . Remove dirt from the starter
motor and solenoid . With the starter motor installed on
the engine, apply reflective paint- Krylon No. 1402 High
Temperature (1,200°F) Aluminum Paint, or equivalentto
all accessible surface areas of the starter motor and
solenoid . This is a temporary measure since any accumulation
of dirt will reduce its effectiveness .
Reference:Chevrolet Dealer Service Technical Bulletin
No. 80-T-27 (March, 1980)
G- and P-Series Models Produced Prior to March 15,
1980-Approx.
On some 1979-80 vehicles, the starter motor may not
engage after the engine has been turned off and allowed
to "hot soak" for a short period of time (10-15 minutes) .
This condition can result from increased starter solenoid
resistance when the solenoid temperature increases. Increased
resistance causes reduced current flow to a point
where the solenoid may not "pull-in." The symptoms are
"no clicking noise" and no cranking when the ignition key
is turned to the start position .
WIRE TO NEUTRAL
START SWITCH
12 GA.(PURPLE)
WIRE ADDED AND CONNECTED
TO CHASSIS GROUND
12 GA. (BLACK)
THESE FOUR WIRES
REMOVED FROM "B+"
JUNCTION BLOCK &
RECONNECTED TO SWITCH
STUD AS SHOWN
12 GA.(RED)
10 GA.(RED)
12 GA.(RED)
10 GA.(RED)
12 GA. (PURPLE) SEVERED ENDS OF SAME
WIRE, TERMINATED AND
ATTACHED TO SWITCH
WIRE TO STARTER MOTOR
"S" TERMINAL
OIL FILLER
TUBE SUPPORT
STARTER MOTOR ENGAGEMENT
AFTER INITIAL START-UP
The following information has been extracted from a
Chevrolet Dealer Service Technical Bulletin concerning
the starter motor relay for 7.4L engines. Problem conditions
and corrective procedures are described .
Reference: Chevrolet Dealer Service Technical Bulletin
No. 84-41 (December, 1983)
1983-84 Motor Home Chassis
The starter motor on some motor home vehicles may reengage
after the engine has been started. This may result
from the starter motor relay being energized after the initial
start-up. Starter damage could result if this should
happen.
To correct the situation, replace the starter relay with a
magnetic switch . (See Figure A7-13-1 .) Remove the relay
connector on the existing engine harness and reterminafe
the wires with the appropriate size ring terminals .
APPENDIX 7- 13
This change was incorporated into production vehicles
after 1984.
NOTE : A square box electrical relay (GM Part No.
356284) was used in production starting October
28, 1982 with the first serial number of
302886. This relay was used until March 3,
1984. Beginning with serial number 328810,
production was switched back to a magnetic
switch (GM Part No. 1115616). Both switch
types are mounted in the same general location.
If a problem arises with electrical relay
GM Part No. 356284, it should be replaced with
either magnetic switch GM Part No. 1115616 or
No. 001486 (interchangeable GM Part Nos.).
Other 4-post, non-GM switches may be electrically
and functionally similar.
GM PART NO. 1114537
MAGNETIC SWITCH
12 GA BLACK
8-32 UNC
THREAD
18 GA BLACK
10 GA RED
12 G_ A'PURPLE
~~ 5/16-24 UNF
THREAD
10 GA PPL
SPACER
OIL FILLER
UBE SUPPORT
Figure A7-13-1- Starter Motor Relay Connections
GENERATOR BELT USAGE ON
6.21. DIESEL ENGINES
The following information has been extracted from a
Chevrolet Dealer Service Technical Bulletin concerning
generator belt usage for 6 .21- engines.
Reference : Chevrolet Dealer Service Technical Bulletin
No. 83-103 (November, 1983)
Belts installed during production were developed to withstand
the characteristics of the 6.21- diesel engine. Usage
APPENDIX 7.14
of substitute belts (with the same dimensions but not construction)
will not give the same performance and may
wear prematurely, even while operating at the prescribed
belt tension .
To obtain optimum belt life, the following belts and tension
settings are recommended to be used with the 6.21- diesel
engine.
Motor Home does not have factory air conditioning
I NOTE : The generator/vacuum pump belt for 1984 G- and P-Series is #14071081 . This is a cog type belt,
49" x 3/8".
Figure A7-14-1 - 6.2L Diesel Engine Belt Usage
BELT TENSION
BELT USAGE RECOMMENDED BELT NEW USED
Generator GM Part No . 14050449 ( .380 HiRide x 48) 175 lbs. 55-100 lbs.
A/C Belt" GM Part No . 14033869 ( .380 HiRide x 60) 175 lbs. 55-100 lbs.
P.S. Belt GM Part No . 14050459 ( .380 HiRide x 45'/2) 175 lbs. 55-100 lbs.
1985-Current A/C Belt GM Part No . 476406 ( .380 HiRide x 61) 175 lbs. 55-100 lbs.
1985-Current Generator GM Part No. 15592119 ( .380 HiRide x 48) 175 lbs. 55-100 lbs.
APPENDIX 7- 15
TORSIONAL ISOLATOR
The 6.2L torsional isolator is now available from GM Parts
Division. The isolator is installed in place of the present
crankshaft pulley . The isolator should be installed to correct
complaints of short belt life. New bolts and washers
are required to install the isolator .
Figure A7-15 -1- Torsional Isolator Parts Identification
GM PART NUMBER MODEL YEAR
15592125 P With Air Conditioning
C, K, G With Air Conditioning
G With Air Conditioning
1982-85
1982-84
1985
15592127 C, K, G, P Without Air_Conditioning 1982-85
1.5592128 C, K With Air Conditioning 1985
Also Required: 4 - Bolts, GM Part No. 11500937
4 - Washers, GM Part No. 9438083
ELECTRONIC CRUISE CONTROL
The GM/AC electronic cruise control is currently available
on G-Series vehicles and is proposed as an option for
1988 P-Series vehicles (under option number K34). The
following information is provided as an aid to the motor
home owner concerning problem conditions that may exist
and corrective procedures are described .
The following provides corrective actions if the electronic
cruise control will not engage:
1 . Turn on the cruise control at the slide switch . Have an
assistant listen near the servo positioned under the
hood of the vehicle . When the ignition is turned ON,
two clicks should be heard. (This means that there are
12 volts being sent through the cruise control slide
switch, through the brake switch and out to the vacuum
and vent solenoid valves in the servo.)
2. Remove the large hose at the servo. Applying suction
by mouth, check for A complete seal. The vacuum
valve should be sealed with the brake pedal released .
When the brake pedal is depressed, you should lose
vacuum. Replace the hose.
3. Start the engine and remove the small hose at the
servo. Check to make sure there is a vacuum with the
engine running . Replace the hose.
4. Turn the engine OFF and leave the ignition ON. Using
a test light or a volt meter check the following positions
and readings at the electronic controller box:
TERMINAL A - 12 volts indicated when the slide
switch is turned on.
TERMINAL G - 12 volts indicated when the brake
pedal is released with the slide switch on.
TERMINAL M - 12 volts indicated when the resume/
accelerate switch is pushed .
TERMINAL L -12 volts indicated when the set/coast
button is pushed with the slide switch on . (This step
checks all mode switches down to the controller.)
5 . To check the vehicle speed sensor, turn the ignition
on and verify voltage to the pink wire at the yellow
speed sensor connector . There should be 12 volts
passing through the wire. Check to show continuity at
the black wire to ground. Using a volt meter, touch
APPENDIX 7" 16
TERMINAL D at the electronic controller with the engine
running . Roll the vehicle slowly five or six feet in
the stall. The volt meter should jump from a zero reading
to between 7-1/2 and 8-1/4 volts. This indicates a
good vehicle speed sensor.
6. Check the servo electrically :
TERMINAL A to C should read - 30 to 55 Ohms
TERMINAL E to C should read - 30 to 55 Ohms
TERMINAL B to D should read - 15 to 25 Ohms
7. If any of the above checks did not provide the cause
of the problem and the cruise controller still does not
operate, the electronic controller box can be presumed
the cause of the problem and should be replaced .
CRUISE CONTROL RESPONSE
A properly adjusted cable will provide a more responsive
"feel" as the diaphragm has less of a chance to bottom
out allowing full engine throttle. A second benefit to a
properly adjusted cable is the overall smoothness of response
by removing play or slack from the cable system
The following is recommended to provide proper cruise
control response:
1 . Adjust the cable from the cruise control 'servo to the
carburetor to obtain the least amount of slack while
still maintaining a normal curb idle .
2 . Lightly squeeze the rubber diaphragm on the servo
control . Feel and observe cable movement as it first
removes any slack and then starts throttle movement.
NOTE: A proper adjustment allows only slight perceptible
movement before the throttle begins.
3 . Adjustment varies by model but generally the adjustment
is performed by removing the pin and moving up
the adjusting holes in a stair-step series fashion .
NOTE: ARA Cruise Control service parts can be obtained
at S.C.S. Frigette, 1200 W. Risinet, Fort
Worth, TX 76140, phone 817-293-5313.
APPENDIX 7-16
ELECTRONIC CRUISE CONTROL
(Cont'd)
CONTROL
MODULE
CONNECTOR
IGN 1
GND
SPEED SIGNAL (C3)
r-
SPEED SIGNAL ma (CRUISE)
CLUTCH SWITCH BRAKE
(OPTIONAL) SWITCH
~-QIP'~v.r~ri.~r7y
E I VAC VALVE
NORMALLY OPEN
CRUISE MODE CONTROL
ENGAGE SWITCH
ON OFF
4-
I RA
3' -SCpr
Figure A7-16-1 - Electronic Cruise Control Schematic 1988 & Prior
ELECTRONIC CRUISE CONTROL
(Cont'd)
DESCRIPTION
The Electro-Motor Cruise Control is a speed control
system which maintains a desired vehicle speed under
normal driving conditions. The Electro-Motor Cruise
Control System has the capability to cruise, coast,
resume speed, accelerate, tap-up, and tap-down.
The main parts of the cruise control system are the
mode control switches, cruise control module, electrical
release switches, and electrical harness .
The cruise control system uses a control module to obtain
the desired vehicle cruise operation (figure 1). Two
important components in the module help to do this.
One is an electronic controller and the second is an
electric motor. The controller monitors vehicle speed
and operates the electric motor. The motor moves a
connecting strap and throttle linkage in response to
the controller motor to maintain the desired cruise
speed. The cruise control module contains a low
speed limit which will prevent system engagement
below about 25 mph. The operation of the controller is
controlled by mode control switches located on the
turn signal lever.
MODEL CONTROL SWITCH
1989-94 ELECTRO-MOTOR CRUISE SYSTEM
The mode control switch controls the various
operating modes of the cruise control system . The
switch is located on the multi-function lever.
VEHICLE SPEED SENSOR 1989
The P. Motorhome Cruise Control system uses only
the input provided by the vehicle speed sensor located
in the back of the speedometer head to maintain
desired speeds. This system does not use vacuum or a
servo.
NOTE : Effective SOP 1994 The previous K34 cruise
control option will now be standard equipment
from the factory.
ELECTRIC BRAKE RELEASE SWITCH
The brake pedal has two switches when a vehicle is
equipped with cruise control . The combination stop
light/cruise control switch is used in series with a
APPENDIX 7-16
separately mounted plunger type release switch. This
is a redundant switch. When the brake pedal is
depressed, each switch disengages the cruise control
system. The cruise function remains disengaged after
the brake pedal is released.
CRUISE CONTROL MODULE
The cruise control module is mounted on the top of the
radiator support on the driver side. The cruise control
module has an electronic controller and an electric
motor to vary the throttle with each different cruise
control mode. The cruise control module is not serviceable
in the field. DO NOT ATTEMPT TO REPAIR
THE MODULE.
NOTE; The factory installed cruise control servo cable
can be ordered separate. #25075767
Figure A7-16-2 - Cruise Control Module
NOTE: Starting in 1991 with the overdrive transmission,
the switch mounted near the top of the
brake pedal bracket controls the Torque Con
vertor Clutch (TCC) in the 4L80EHD Transmission
.
Additional information see bulletin #90-368-8C
Page4 or Bulletin 91-137-9 Page 1
ELECTRONIC CRUISE CONTROL
(Cont'd) -
IGNITION "OFF"
WITH OHMMETER MEASURE RESISTANCE
OF BLK/WHT WIRE (450) FROM
TERMINAL E OF C4A TO ENGINE BLOCK
GROUND STUD.
LESS THAN 1 OHM
MEASURE VOLTAGE AT TERMINALS A,
B, C, D OF C4A TO GROUND WITH
CRUISE LEVER SWITCH OFF AND IGNITION
ON.
0 VOLTS AT ALL TERMINALS
MEASURE VOLTAGE AT TERMINALS B
AND C OF C4A TO GROUND WITH
CRUISE AND IGNITION SWITCHES ON.
APPENDIX 7-16
CHART A
IGNITION OFF
DISCONNECT CONNECTOR C4A FROM
CRUISE MODULE.
IGNITION "ON"
MEASURE VOLTAGE AT TERMINAL F OF
C4A TO A GOOD GROUND .
REPLACE CRUISE CONTROL LEVER
CHECK GAGES FUSE AND
SPEEDO FUSE.
CHECK PNK WIRES (39A, 39B) AND
PINK/BLK WIRES (39A, 39C) FOR OPEN.
GREATER THAN 1 OHM
CHECK ENGINE BLOCK GROUND STUD FOR A
CLEAN AND TIGHT CONNECTION. CHECK CONDITION
OF BLK/WHT WIRE (450) FROM TERMINAL
E OF C4A TO ENGINE BLOCK GROUND STUD.
12 VOLTS AT ONE OR MORE TERMINALS
" DISCONNECT CONNECTOR C3A. MEASURE
VOLTAGE AGAIN AT TERMINALS A, B, C, AND D
OF CONNECTOR C4A.
" IF ALL TERMINALS READ ZERO VOLTS, REPLACE
CRUISE CONTROL LEVER.
" IF ONE OR MORE TERMINALS READ 12 VOLTS,
PROBLEM IS IN WIRING HARNESS.
Figure A7-16-3 - Diagnosis of the Cruise Control System - Chart A
7-89
APPENDIX 7-16
ELECTRONIC CRUISE CONTROL
(Cont1d)
0 VOLTS AT A AND D
" CHECK FOR 12 VOLTS AT TERMINAL
A OF FEMALE HALF OF CONNECTOR
C3A. IF ZERO VOLTS, CHECK FOR
OPEN IN PNK WIRE (39C).
" CHECK CONTINUITY BETWEEN TERMINALS
A AND B OF MALE HALF OF
C3A WITH CRUISE SWITCH ON . IF
OPEN, REPLACE CRUISE CONTROL
LEVER.
" CHECK FOR OPEN IN GRA WIRE
j397B) .
" PUT VOLTMETER ON DC VOLTAGE
SCALE.
" CONNECT VOLTMETER ACROSS PINS
F AND K OF CONNECTOR C4A.
" IGNITION ON, RAISE VEHICLE, PUT
TRANSMISSION IN NEUTRAL.
" SPIN DRIVE WHEELS BY HAND.
12 VOLTS
MEASURE VOLTAGE AT TERMINAL C OF
C4ATO GROUND WITH CRUISE SWITCH
IN R/A POSITION .
CHART B
FROM CHART A ,
MEASURE VOLTAGE AT TERMINALS A AND D OF C4A TO
GROUND WITH, CRUISE LEVER SWITCH AND IGNITION SWITCH ON.
0 VOLTS ONLY AT D
" CHECK FOR OPEN OR MISADJUSTED
BRAKE SWITCHES .
" CHECK FOR OPEN IN BRAKE/CLUTCH
SWITCH WIRING FROM SPLICE S2AA
TO TERMINAL D OF C4A.
12 VOLTS AT A AND D
CRUISE SWITCH ON AND "SET" PUSH
f BUTTON DEPRESSED.
MEASURE VOLTAGE AT TERMINAL B OF
C4A TO GROUND.
0 VOLTS
" DISCONNECT C3A AND CHECK CONTINUTIY
BETWEEN TERMINALS A
AND, C OF MALE HALF WITH WITH
CRUISE SWITCH IN R/A POSITION . IF
OPEN, REPLACE CRUISE CONTROL
LEVER.
" CHECK FOR OPEN IN DK GRN WIRE
(83) .
0 VOLTS ONLY AT A
CHECK FOR AN OPEN
IN GRA WIRE (397A) .
0 VOLTS
" DISCONNECT CONNECTOR C3A AND
CHECK CONTINUITY BETWEEN TERMINALS
B AND D OF MALE HALF
WITH "SET" PUSH BUTTON DEPRESSED.
IF OPEN, REPLACE CRUISE
CONTROL LEVER.
" CHECK FOR OPEN IN DK BLU WIRE
(84) .
Figure A7-16-4 - Diagnosis of the Cruise Control System - Chart B
7-90
APPENDIX 7-16
ELECTRONIC CRUISE CONTROL
(Cont'd)
VOLTAGE VARYING BETWEEN
ZERO AND 12 VOLTS.
RECONNECT CRUISE MODULE
CONNECTOR C4A.
" START ENGINE
" MOVE CRUISE SWITCH TO ''OFF"
" MOVE CRUISE SWITCH TO "ON' AND THEN WAIT
AT LEAST 3 SECONDS BEFORE DOING NEXT STEP.
" FULLY DEPRESS AND HOLD BRAKE PEDAL.
" PUSH CRUISE "SET" PUSH BUTTON IN AND HOLD.
" HOLD CRUISE SLIDER SWITCH IN "R/ A" POSITION .
" AFTER 10 SECONDS, RELEASE BRAKE PEDAL
AND LISTEN FOR MOMENTARY ENGINE RPM
INCREASE .
ENGINE RPM INCREASE .
" PROBLEM IS INTERMITTENT .
" CHECK CONNECTORS AND WIRE TERMINALS
FOR CONTAMINANTS (OIL, GREASE, DIRT)
AND FOR PROPER CONTACT.
" ALSO CHECK GROUND TERMINALS
FOR CONTAMINANTS AND CONTACT .
CHART C
FROM CHART B
0' VOLTS
y--
_
CHECK FOR OPEN ON BRN/WHT
WIRE (437 AND 437A) .
NO OPENS OR SHORTS IN WIRE .
REPLACE VEHICLE SPEED SENSOR.
NO ENGINE RPM INCREASE .
" CHECK THAT CRUISE MODULE LINKAGE IS
CONNECTED AND OPERATING FREELY.
" CHECK LINKAGE ADJUSTMENT.
" CHECK TERMINALS IN CONNECTORS
C3A, C4A, C5A FOR CONTAMINANTS
(OIL, GREASE, DIRT) AND FOR
PROPER CONTACT . IF OK, REPLACE
CRUISE CONTROL MODULE .
[
12 VOLTS
CHECK FOR SHORT TO GROUND
ON BRN/WHT WIRES (437, 437A)
Figure A7-16-5 - Diagnosis of the Cruise Control System - Chart C
Additional information and diagnostics can be found in
the C-K Pickup Shop Manual for the EMCS cruise control .
VEHICLE EMISSION CONTROL
INFORMATION LABEL
The Vehicle Emission Control Information Label (Figure
7-56) is located in the engine compartment (fan shroud,
radiator support, hood underside, air cleaner, etc .) of
every vehicle produced by General Motors Corporation .
The label contains important emission specifications and
setting procedures, as well as a vacuum hose schematic
with emission components identified.
When servicing the engine or emission system, the Vehicle
Emission Control Information Label should be
checked for up-to-date information .
EMISSION CONTROLS --
SYSTEMS ANDCOMPONENTS
GENERAL DESCRIPTION
POSITIVE CRANKCASE VENTILATION
(PCV) SYSTEM - GASOLINE ENGINE
Because small amounts of combustion gases seep past
the piston rings, all engines have a closed Positive Crankcase
Ventilation System to provide more complete scavenging
of crankcase vapors (Figure 7-57).
ZFT I IMPORTANT ENGINE IN ..MATRON
"NGYO7MWN7 GENERAL MOTORS " ' .NBATION
SET PARKING BRAKE AND BLOCK DRIVE WHEELS.
SECTION 7F-ENGINE EMISSION CONTROLS
ENGINE EMISSION CONTROLS
LABEL CODE
ENGINE SIZE
EXHAUST EMISSION FAMILY
EVAPORATIVE EMISSION FAMILY
ADJUSTMENT
PROCEDURE
MAKE ADJUSTMENTS WITH ENGINE AT NORMAL OPERATING TEMPERATURE, CHOKE FULL OPEN, AIR
CLEANER INSTALLED AND AIR CONDITIONING OFF . PUT TRANSMISSION IN PARK OR NEUTRAL FOR ALL
SETTINGS .
1. DISTRIBUTOR: DISCONNECT AND PLUG VACUUM HOSE AT DISTRIBUTOR . SET IGNITION TIMING
AT SPECIFIED ENGINE SPEED . UNPLUG AND RECONNECT VACUUM HOSE TO DISTRIBUTOR.
2. IDLE SPEEDSCREW : ADJUST IDLE SPEED SCREW TO SPECIFIED SPEED.
S. FAST IDLE SPEED SCREW: DISCONNECT AND PLUG VACUUM HOSE AT EGR VALVE, CANISTER
PURGE HOSE AND CANISTER PURGE SIGNAL HOSE AT CANISTER . ADJUST FAST IDLE SPEED SCREW
TO SPECIFIED SPEED WITH LIVER ON HIGH STEP OF CAM. UNPLUG AND RECONNECT HOSES TO EGR
VALVE AND CANISTER .
FUEL REQUIREMENTS - USE 89 OCTANE OR HIGHER .
THIS ENGINE CONFOINS TO U.S. EPA REGULATIONS APPLICABLE TO 1987 MODEL YEAR NEW HEAW DUTY ENGINES . THIS
[ONE IS CERTIFIED FOR USE IN ALL HEAVY-DUTY VEHICLES.
A.I.R./E.G.R.
IDLE SPEED SCREW (RPM) 700
AUTOMATIC
TIMING ( "BTC ® RPM) A " ® 700
FAST IDLE SPEED SCREW (RPM) 1900
SPARK PLUG GAP (IN .) O.0A5
VALVE LASH HYD .
IDLE MIXTURE SCREWS ARE PRESET AND
T FACTORY. PROVISION FOR ADJUSTMENT
WRING TUNE-UP IS HQj PROVIDED. SEF SERVICE
MANUAL. MAINTENANCE-SCHFDULE AND EMISSION
HOSE ROUTING DIAGRAM FOR ADDITIONAL
INFORMATION .
Figure 7-56- Vehicle Emission Control Information Label
7-92
bF = FILTERED
AIR
00 B = BLOW-BY
GASES
7*F+B
COMBUSTIBLE MIXTURE
CRANKCASE
BLOW-BY
GASES
Figure 7-57 -PCV System -Gasoline Engine
-Typical
ENGINE ADJUSTMENT
SPECIFICATIONS
EMISSION COMPONENT
AND VACUUM HOSE SCHEMATIC
SECTION 7F
Ventilation air is drawn through a separate filter from the
"dirty air" side of the air cleaner, through a hose down
into the crankcase, up through the ventilator valve,
through another hose and into the intake manifold . The
intake manifold vacuum draws any fumes from the crankcase
to be burned in the engine.
Periodically check for oil deposits in the air cleaner. The
system has been designed as a closed system. If there
are oil deposits on the air cleaner element or a puddle of
oil found at the bottom of the air cleaner base, check the
entire system for oil leaks. A leak in the system will allow
reverse air flow from pulldown with the carburetor air flow
drawing oil fumes out of the right-hand rocker cover into
the air cleaner. Potential leak points include an incorrect
oil fill cap, a leak at the dipstick or rocker cover. (See
Figure 7-58.)
Figure 7-58-Dipstick and Tube Assembly Potential
Leak Points
CRANKCASE VENTILATION -
DIESEL ENGINE
A Crankcase Depression Regulator Valve is used to regulate
(meter) the flow of crankcase gases back into the
engine. The Crankcase Depression Regulator Valve
(CDRV) is designed to limit vacuum in the crankcase as
the gases are drawn from the valve cover through the
CDRV and into the intake manifold (air crossover) .
ENGINE EMISSION CONTROLS
Fresh air enters the engine through the combination filter,
check valve and oil fill cap. The fresh air mixes with blowby
gases and enters the right cover. The gases pass
through a filter on the valve cover and are drawn into the
connecting tubing .
The intake manifold vacuum acts against a spring-loaded
diaphragm to control the flow of crankcase gases.
Higher intake vacuum levels pull the diaphragm closer to
the top of the outlet tube. This reduces the amount of
gases being drawn from the crankcase and decreases the
vacuum level in the crankcase. As the intake vacuum
decreases, the spring pushes the diaphragm away from
the top of the outlet tube, allowing more gases to flow to
the intake manifold .
EARLY FUEL EVAPORATION (EFE) SYSTEM
- GASOLINE ENGINE
The EFE system is used to provide a source of rapid heat
to the engine induction system during cold driveaway.
Rapid heating is desirable because it provides for quick
fuel evaporation and more uniform fuel distribution to aid
cold drivability . It also reduces the length of time carburetor
choking is required, making reductions in exhaust
emission levels possible.
EFE systems may use a valve which increases the exhaust
gas flow under the intake manifold during cold engine
operation. The valve is vacuum-operated and is
controlled by a thermal vacuum switch (TVS) which applies
vacuum when the coolant temperature is below the
calibration valve.
THERMOSTATIC AIR CLEANER
(THERMAC) -GASOLINE ENGINE
The Thermostatic Air Cleaner (THERMAC), shown in
Figure 7-59, uses a damper door in the air cleaner inlet,
controlled by a vacuum diaphragm motor to mix preheated
and nonpreheated air entering the air cleaner to maintain
a controlled air temperature into the carburetor. The vacuum
motor is modulated by a temperature sensor in the
air cleaner. The preheating of the air cleaner inlet air
allows leaner carburetor and choke calibrations resulting
in lower emission levels, while maintaining good
drivability .
The preheated air is obtained by drawing inlet air through
a stove attached to the exhaust manifold .
On vehicles which have been converted to burn LPG- or
CNG-type fuel, by the motor home body manufacturer,
the GM air cleaner and Thermac system may have been
removed . This can result in a cold engine stumble especially
atcold temperatures, when operating on gasoline
as opposed to LPG- or CNG-type fuels .
SECTION 7F-ENGINE EMISSION CONTROLS
THERMAC AIR CLEANER ASSEMBLY
VACUUM HOSE TO INTAKE
MANIFOLD TEE
Figure 7-59 -Thermac Air Cleaner-Typical
zzc
*FT. 110. 100"50
Figure 7-60- Vehicle Evaporative Emission
Control Information Label
EVAPORATIVE EMISSION
CONTROL SYSTEM (EELS)
GENERAL DESCRIPTION
The Vehicle Evaporative Emission Control Information label
(Figure 7-60) contains the government regulations for
the evaporative emission control system, vapor storage
requirements and fuel tank capacity for the evaporative
system.
The Evaporative Emission Control System (EECS) shown
in Figure 7-61 limits the amount of fuel vapor into the
atmosphere. The system traps fuel vapor from the fuel
tank and carburetor float bowl into a fuel vapor canister .
The fuel tank has a non-vented fuel cap and a single vent
pipe to the canister. The canister absorbs and stores the
fuel vapor in a carbon element until it can be removed
and burned during the normal combustion process. When
the engine is running, a thermostatic vacuum switch determines
when the fuel vapor is purged into the intake air
flow.
V®IKAE EVAPORATIVE MSSNNI COMM INFORMATION
GENERAL MOTORS EORPORATION
EVAPORATIVE EMISSION FAMILY NoM080.00EAl
MAXIMUM CERTIFIED FUEL TANK CAPACITY 00 GALLONS
FOR EVAPORATIVE SYSTEM (NOMINAL)
VAPOR STORAGE TWO CANISTERS
PLUS AIR CLEANER
=O11S CORMTDO N" OETIENIED THAT THIS V61NE CarGRAS TGG. . 1P. 114119-T=5
Y1lKYlE TO 1W 11006 YEAR NEW OA50M-ERR HEAVY-OIITT VENC16 WIBI LOAVES®VNTN A
110NEEM RR TASK CAPACITY
UK
ToUM 60 GAl1ONS.
ASOIN WIS1101 TO ADD RAN, TAR WACITT YTOID THE AMVA MA%OEW MUST RESENT A 1110TIN1
STATB101T 10 THE VA ARIIR1UTOR THAT THE NSOMCAROO STORAGE STAR 11At 1N1 UPGRADED
ACCORID To TIN RaADrNnsa Io Cn 11187-190
SECTION 7F - ENGINE
TO TCC ON A/T,
TO EGR ON M/T
CANISTER
PURGE VALVE ASM. -
CONTROL VALVE BOWL VENT
ACTIVATED
CARBON
ELEMENT
VAPOR
RESTRICTION I
CARBURETOR
ASSEMBLY
Figure 7-61- Evaporative Emission Control System (EECS)
The Evaporative Emission Control System uses the following
control valves:
e Purge control valve mounted on the canister .
e Vapor vent valve mounted on the canister.
e A thermal bowl vent valve (some applications) .
e A thermostatic vacuum switch (TVS) installed in the
intake manifold to sense engine coolant temperature .
When the engine is shut off, manifold vacuum is lost at
the vapor vent valve. The spring-loaded valve in the vapor
vent valve now connects the carburetor bowl vent to the
canister. Carburetor float chamber vapors now pass into
the canister for storage. When the engine is restarted,
manifold vacuum draws the vapor vent controlling valve
against spring pressure, closing off the bowl vent. Ported
vacuum from the carburetor is connected to the TVS.
When the TVS opens, ported vacuum opens the purge
control valve. When the valve opens, manifold vacuum
draws vapors from the canister into the intake manifold.
EMISSION CONTROLS
The thermal bowl vent valve (TBVV) is located in the
section of hose that connects the carburetor bowl vent
fitting to the canister control valve.
The TBVV will close and prevent vapor movement at 32°C
(90°F) and below. The TBVV will open at 49°C (120°F) to
permit vapor flow to the canister control valve.
FUEL VAPOR CANISTER-PRIMARY
The basic large-size, two-chamber, closed bottom primary
fuel vapor canister is shown in Figure 7-62. This canister
is used on all systems.
Gasoline vapors from the fuel tank flow into the tube labeled
"FUEL TANK," and vapors from the carburetor float
bowl flow into the tube labeled "CARB BOWL," and are
absorbed by the carbon. The canister is purged when the
engine is running above idle speed. The closed bottom
design keeps water from entering the bottom of the canister,
freezing, and restricting purge air flow. During purge,
air is drawn from the clean side of the air cleaner, to the
SECTION 7F ENGINE EMISSION CONTROLS
10
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D
0 LARGE SIZE TWO
CHAMBER CLOSED'
BOTTOM CANISTER
VAPOR VENT CONTROL
VALVE
PURGE CONTROL VALVE
CLEAN AIR TUBE "AIR
CLNR"
VAPOR FROM FUEL TANK
VAPOR FROM BOWL VENT
TO MANIFOLD VACUUM
SIGNAL
TO PORTED VACUUM
VAPOR TO PURGE LINE
FILTER
CARBON
BOTTOM COVER
DUST CAP
AIR FLOW
Figure 7-62 - Fuel Vapor Canister -- Primary
tube on the canister labeled "AIR CLNR," through the
carbon and into the intake manifold to be burned. Some
closed bottom canisters draw purge air directly from the
atmosphere.
Canister Purge Control Valve
The canister purge control valve shown in Figure 7-62 is
a spring-biased diaphragm valve, normally closed, which
allows or prevents purging of the canister . When the engine
is off or idling, the spring holds the valve closed
preventing canister purge. When the engine is off idle,
however, timed manifold vacuum pulls the diaphragm upward
and opens the valve allowing the canister to be
purged.
Vapor Vent Control Valve
The vapor vent control valve shown in Figure 7-62 prevents
venting of the carburetor float bowl during engine
operation. A spring-biased diaphragm valve, normally
open, allows (or prevents) fuel vapors from the float bowl
to enter the canister. When the engine is off, spring tension
holds the valve open, allowing normal venting .
When the engine is turned on, however, manifold vacuum
pulls the diaphragm up to the valve.
7-96
FUEL VAPOR CANISTER - AUXILIARY
An Auxiliary Fuel Vapor Canister shown in Figure 7-63 is
added to a primary closed bottom canister to increase
capacity when a dual (auxiliary) fuel tank is used. On the
bottom is a hose which connects to the primary canister's
purge air inlet. On top is a purge air inlet. Vapor overflowing
from the primary canister is stored in the auxiliary
canister. During purge, vapor flows through the auxiliary
canister, the primary canister and into the intake manifold
for burning during combustion.
CARBON
AUXILIARY DUST CAP
CANISTER
AIR FLOW
] DURING PURGE
*.1404000,
FILTERS
*,VAPORS FROM
PRIMARY CANISTER
Figure 7-63- Fuel Vapor Canister -Auxiliary
SECTION 7F
MAINTENANCE AND INSPECTION
POSITIVE CRANKCASE VENTILATION (PCV)
- GASOLINE ENGINE
An engine which is operated without any crankcase ventilation
can be damaged seriously . Therefore, it is important
to replace the PCV valve (GM Part No. 6487779; AC
CV774C or equivalent - 5.71- and Mark IV engines) at
the recommended intervals.
If an engine is idling too slowly or roughly, this may be
caused by a clogged ventilator valve or plugged hose;
therefore, never adjust the carburetor idle without first
checking the PCV valve and hose.
With this system any blow by in excess of the system
capacity (from a badly worn engine, sustained heavy load;
etc.) is exhausted into the air cleaner and is drawn into
the engine.
Proper operation of the PCV System is dependent on a
sealed engine. If oil sludging or dilution is noted, and the
PCV System is functioning properly, check engine for possible
cause and correct to ensure that the system will
function as intended.
Checking the PCV System
1 . Remove PCV valve from intake manifold or rocker arm
shaft cover.
2. Run the engine at idle.
3. Place your thumb over end of valve to check for
vacuum. If there is no vacuum at valve, check for
plugged hoses or valve. Replace plugged and/or deteriorated
hoses.
4. Shut off engine and remove PCV valve. Shake valve
and listen for the rattle of check needle inside the valve.
If valve does not rattle, replace valve (Figure 7-64).
Remove PCV valve from rubber hose and look up the
end of the hose using a flashlight. If the hose appears
coated "oil wet," replace the PCV valve.
5. After installing a new PCV valve, readjust engine idle
if necessary.
EARLY FUEL EVAPORATION (EFE)
Inspection
" Visually inspect the exhaust heat valve (Figure 7-65)
for damage or binding linkage.
" Check that the linkage is connected and the vacuum
hoses are properly routed and connected.
" Move exhaust heat valve by hand. If binding or stuck,
free it with manifold heat valve lubricant, GM Part No.
10504022 or equivalent. If the valve cannot be freed,
replace the valve.
ENGINE EMISSION CONTROLS
7-97
Figure 7-64- PCV Valve
Checking EFE System
1 . With the engine cold, position the transmission in neutral
or park and apply parking brake.
2. Start the engine and observe movement of the actuator
rod and exhaust heat valve. Valve should move to its
closed position.
3. If the valve does not close, disconnect the hose at the
actuator and check for vacuum.
" If there is vacuum, replace the actuator .
" If . there is no vacuum, disconnect the hose at the
TVS to vacuum source.
" If there is vacuum at the hose, replace the TVS.
" If there is no vacuum, check for deteriorated hose
and vacuum source to determine the lack of vacuum.
4. When the coolant reaches 180°F, the exhaust heat
valve should move to its open position .
5. If the valve does not move, disconnect the hose at the
actuator and check for vacuum.
" If there is vacuum, replace the TVS.
" If there is no vacuum, replace the actuator .
AIR INJECTION REACTOR (A.I.R.) SYSTEM
-GASOLINE ENGINE
The Air Injection Reactor (A.I.R.) System (Figure 7-66)
consists of: an air injection pump (with necessary brackets
and drive attachments), an air diverter valve, a check
valve, and an air pipe assembly for each exhaust manifold,
and connection hoses.
SECTION 7F-ENGINE EMISSION CONTROLS
Figure 7-65 - Exhaust Heat Valve-EFE System
Inspection
Accelerate the engine to approximately 1,500 RPM and
observe air flow from the hose(s). If the air flow increases
as the engine is accelerated, the pump is operating satisfactorily
. If the air flow does not increase or is not present,
proceed as follows :
1 . Check for proper drive belt tension . The A.I.R. system
is not completely noiseless. Under normal conditions,
noise rises in pitch as engine speed increases.
To determine if excessive noise is the fault of the system,
operate the engine with the pump drive belt removed. If
excessive noise does not exist with the belt removed,
proceed as follows :
2. Check for a seized air injection pump. Do not oil the
pump.
3. Check hoses,. pipes and all connections for leaks and
proper routing .
NORMAL FLOW SHOWN BY BLACK
ARROWS: BYPASS CONDITIONS
SHOWN BY CROSSHATCHED
ARROWS.
AIR PUMP
,.W
DECELERATION
BYPASS DIVERTER
VALVE
HIGH SPEED
BYPASS
."IIUv.
MANIFOLD VACUUM
SOURCE
TUBE ASSEMBLY
EXHAUST PORT
Figure 7-66-Air System - Typical
7-98
5 . Check injection pump for proper mounting and bolt
torque.
6 . Repair irregularities in these components as
necessary.
7. If no irregularities exist and the air injection pump noise
is still excessive, remove and replace the pump.
2. Loosen the alternator adjustment bolt.
3. Replace the belt if required .
SECTION 7F- ENGINE EMISSION CONTROLS
4. Check diverter valve attaching screws for tightness .
Air Pump Drive Belt Adjustment and
Replacement
1 . Inspect drive belt for wear, cracks and deterioration .
4. Move the alternator or pump until the drive belt is at
the proper tension, then retighten bolts. See Appendix
A- Drive Belts and Tension Specifications at the back
of this manual for specifications .
5. Check the belt tension using a belt tension gage.
CHECK VALVE INSPECTION
1 . The check valve should be inspected whenever the
hose is disconnected from the check valve or whenever
check valve failure is suspected. (A pump that
had become inoperative and had shown indications of
containing exhaust gases in the pump would indicate
check valve failure.)
2. Blow through the check valve (toward the cylinder
head) then attempt to suck back through check valve.
Flow should only be in one direction (toward the exhaust
manifold). Replace valve which does not function
in this manner.
THERMOSTATIC AIR CLEANER
Checking Thermac Air Cleaner
1 . Inspect the system to be sure all hoses and tubes are
connected. Check for kinked, plugged or deteriorated
hoses .
2. If the engine is warm or above 80°F, remove the air
cleaner, Allow it to cool to room temperature, below
80°F. Place a cool wet rag on the temperature sensor
to aid in cooling .
3. Install the cooled air cleaner with cold air intake disconnected
from snorkel (if equipped) .
4. Observe the damper door before starting the engine.
It should be in the open snorkel position (hot air duct
covered .)
7-99
5. Start the engine. Watch the damper door in the air
cleaner snorkel . When the engine. is first started, the
damper door should close. As the air cleaner warms
up, the damper door should open slowly.
6. If the damper door does not close when the engine is
started, remove the air cleaner .
7. Apply at least 7 in. of vacuum to the vacuum diaphragm
motor through the hose disconnected at the temperature
sensor. The damper door should completely
block off the snorkel passage when vacuum is applied .
If not, check to see if the linkage is hooked up correctly .
8. With the vacuum still applied, trap vacuum in the
vacuum diaphragm motor by bending the hose. The
damper door should remain closed ; if not, replace
the vacuum diaphragm motor assembly. (Failure of
the vacuum diaphragm motor assembly is more
likely to be caused by binding linkage or a corroded
snorkel than by a failed diaphragm. This should be
checked first, before replacing the diaphragm.)
9 . Reinstall the air cleaner. As the engine warms up, the
damper door should start to allow outside air and
heated air to enter the carburetor.
10 . If the air cleaner fails to operate as described above
or if the correct operation of the air cleaner is still in
doubt, perform a thermometer check of sensor.
Thermometer Check of Sensor
1 . Start the test with the air cleaner temperature below
80°F. If the engine has been run recently, remove the
air cleaner and place the thermometer as close as
possible to the sensor. Let the air cleaner cool until
the thermometer reads below 79°F, about 5 to 10 minutes.
Reinstall the air cleaner on the engine and continue
to Step 2 below.
2. Start and idle engine. The damper door should move
to close the snorkel passage immediately if the engine
is cool enough. When the damper door starts to open
the snorkel passage (in a few minutes), remove the air
cleaner cover and read the thermometer . It must read
between 100°F and 130°F.
3. If the damper door does not start to open up the snorkel
passage at the temperature indicated, the temperature
sensor is malfunctioning and must be replaced.
Air Cleaner Element and PCV Filter
Replacement
PAPER ELEMENT -
1 . Remove the air cleaner cover.
2. Remove the air cleaner element and PCV filter.
3. Install anew element and PCV filter in the air cleaner .
SECTION 7F - ENGINE EMISSION CONTROLS
4. Reinstall the air cleaner cover. Do not overtighten
wing nut.
POLYWRAP ELEMENT (P-SERIES) -
1 . Remove the air cleaner cover.
2. Remove the element.
3. Remove the polywrap band from the paper element
and discard the element (Figure 7-67).
4. Clean the bottom section of the air cleaner and inspect
the cover seal for tears or cracks. Replace the
seal if damaged.
5. Inspect the band for tears and replace if damaged.
6. If the band is serviceable, wash it in kerosene or
mineral spirits and squeeze out the excess solvent .
NOTE : Some models and years do not use the Polywrap Air Cleaner System. Some models and years are
equipped with a molded charcoal evaporative filter that is permanently attached to the air cleaner base.
DO NOT ATTEMPT TO REMOVE OR SERVICE THIS FILTER. The function of this filter is to collect
fuel vapors on engine shutdown. This filter "self-purges" as the engine is running . (See Figure 7-61).
POLYWRAP AIR
CLEANER ELEMENT
(BAND SHOWN)
MOLDED
CHARCOAL
EVAPORATIVE
FILTER
n
NOTE: POLYURETHANE
BAND MUST WRAP
OVER BOTH END
SEALS OF PAPER
ELEMENT AS
SHOWN
PAPER FILTER PORTION
OF POLYWRAP AIR
CLEANER ELEMENT
NOTE: POLYURETHANE BAND
MUST COMPLETELY
COVER THE OUTER
SCREEN SURFACE OF
PAPER ELEMENT AS
SHOWN .
WING NUT
TORQUE AT 20 IN. LBS.
AIR CLEANER
ELEMENT
(PAPER FILTER
PORTION)
POLYWRAP
AIR CLEANER
ELEMENT
(BAND SHOWN)
NOTE: 1993-94 uses double stud and wing nut .
Figure 7-67- Polywrap Air Cleaner
7-100
NOTE: Never use a hot degreaser or any solvent containing
acetone or similar solvent ; also, never
shake, swing or wring the element to remove excess
solvent as this may tear the polyurethane
material . Instead, "squeeze" the excess solvent
from the element. Squeezing will avoid damaging
the element material.
7. Dip the band into light engine oil and squeeze out the
excess oil .
8. Install the band around the outer surface of the new
paper element.
9. Install the element in the bottom section of the air
cleaner with either end up.
10. Install the air cleaner cover. Do not over-torque the
wing nut(s) .
H,51) EMISSION SYSTEM
On vehicles equipped with the H5D emission system (vehicles
rated over 8,600 GVW and built after January 1,
1985), the "CHECK ENGINE" light may light up to inform
the motor home owner of a possible problem while a problem
does not actually exist. The following diagnostic procedure
should be followed in correcting this condition .
NOTE : The "CHECK ENGINE" light will normally come
on when the ignition is turned to the "ON" position
and the engine is NOT running . This is provided
as a bulb check.
SOLENOID
CONNECTOR
IGNITION 1
SOLENOID
CONNECTOR
AIR DIVERT TO AIR
SOLENOID CLEANER OR SILENCER
TO EXHAUST
PORTS
A
B
D
93
AIR DIVERT TO AIR
SOLENOID CLEANER
O~ CHECK VALVE
I'r1 CHECK
VALVE
TO EXHAUST
PORTS
SOLENOID
CONNECTOR
"CHECK ENGINE"
LIGHT
CONTROL
MODULE
Figure A7-17-1- A.I.R. Connector Diagram
APPENDIX 7-17
The illumination of the "CHECK ENGINE" light indicates
that there is a malfunction in the A.I.R. solenoid control
module or wiring . (See Figure A7-17-1 .) Perform the following
corrective procedure :
1 . Check the A.L.R. solenoid and A.I.R. moduled connectors
for a proper connection.
2. With ignition on, disconnect each solenoid connector
and with a test light, check for a light across the terminals.
(See Figure A7-17-2.)
H51) EMISSION SYSTEM
(Cont'd)
TYPICAL MOUNTING
LOCATION FOR ELECTRIC
FUEL PUMP RELAY
IF EQUIPPED - GM
PART NO. 15528707.
(See Figure A7-7-4
and Figure A7-7-5 .)
BRACKET
(FLOOR PANEL)
NOTE : TYPICAL FACTORY LOCATION FOR
MOTOR HOME AND COMMERCIAL
"P" MODEL.
A.I .R. CONVERTER
MODULE ASSEMBLY
RADIATOR
ASSEMBLY
Figure A7-17-2-A.I.R. Connector Module and Electric Fuel Pump Relay Locations 1989 & Prior
3. If O.K. (light on), check solenoid coil resistance and if
less than 20 ohms, replace the solenoid and valve.
4. If not O.K. (light off), connect the solenoid connector(s)
and disconnect connector at module. With a test light,
check for a light between terminal "A" and "B."
APPENDIX 7-17
5. If not O.K. (light off), check for an open circuit to the
module.
6. If O.K. (light on), replace the module. (See parts listing
in Figure A7-17-4.)
Figure A7-17-3-H5D Override Relay
APPENDIX 7-17
H51) EMISSION SYSTEM
(Cont'd)
OVERRIDE -
RELAY
(454 ONLY)
A.I.R . DIVERT MODULE
NOTE : A.I.R. DIVERT MODULE
FOR "C" TRUCKS IS
MOUNTED ON THE
FIREWALL
ENGINE
HARNESS
FRONT
NOTE: 1985-1990 models equipped with the LE8 (454) and H5D have an override relay. (See Figure A7-17-3) . This
relay is necessary dur to the lower cranking speed of the LE8 (454) engine. If the relay fails, the CEL will
come on. If it becomes necessary to replace the relay or the module, use the part numbers listed in
Figure A7-17-4.
Figure A7-17-4 - 454 and H5D Override Relay Parts List
7-103
GM PART NO. DESCRIPTION & APPLICATIONS QUALITY
100669221 Module 1985-89 W/LE8 454 1
14087500 Module 1985 W/LT9 350 1
14102010 Module 1986 W/LT9 350 1
14100876 Module 1985-Current W/L25 292 1
15528707 Relay 1985-89 W/LE8 454 1
14103304 Relay 1990-1993 N/L19 454 1
10052973 Module 1990-1993 N/L19 454 1
10052954 Module 1994 N/L19 454 1
APPENDIX 7.17
H51) EMISSION SYSTEM
(Cont'd)
10052954 (4815A)
11501907 (4815K)
0
19
MOOUIE ASM
STRAP
a~u~a
The 1990 fuel module Part #10052973 is connected to cycler override module is necessary due to the lower
the instrument panel wiring harness . The module and cranking speed of the L19 (454) engine. The module
instrument panel wiring harness are shipped loose overrides the ECM for 20 seconds to provide fuel
and must be installed by the body builder. This fuel pressure to the injector.
APPENDIX 7-17
H51) EMISSION SYSTEM
(Cont1d)
Figure A7-17-5 - A.I.R. Pump Failure - 1985 112 thru 1989 454 H5D Emissions
Due to the relocation of the A.I.R. Pump Filter Canister
to the right front wheel well by the body builder, the canister
must be sealed or shielded to prevent water, salt and
dirt thrown by the tire to enter the A.I.R System through
the hose connections at the bottom of the canister and/
or through the lid at the top of the canister . See Figure
A7-17-5. The air inlet hose must also be located away
from direct water spray and sealed where it is attached
to the core support.
Sealing the canister can be accomplished by applying a
bead of Permatex No. 2 Sealer, or equivalent, to the canister
hoses and lid .
1 . Loosen inlet and outlet hose clamps and remove hoses
from A.I .R. Filter Canister . Clean hose connections.
2. Remove and clean canister lid .
7-105
3. Apply a bead of Permatex No. 2 Sealer, or equivalent,
to the canister inlet and outlet hose connections and
inside circumfrence of the canister lid. Reinstall lid and
hoses.
4. Tighten hose clamps securely.
NOTE : Production mounting of the A.I.R. Filter Canister
is in the vertical position (canister lid facing up) .
An alternative method of eliminating water con
tamination would be to remount the canister horizontally
(lid facing the right side of the vehicle),
and rotate the canister in the clamp so that the
two air outlets are positioned in the 11 o'clock
and the 1 o'clock positions . (See Figure A7-17.5.)
Positioning the canister in this manner eliminates
the need to seal the canister or hoses as described
above.
GENERAL DESCRIPTION
The transmission (Figure 8-1) is mounted behind the engine.
Its function is to convert the power output of the
engine into usable power for the drive wheels of the motor
home. By activating different gears within the transmission,
the speed at which the output shaft of the transmission
turns in relation to the speed of the engine crankshaft
can be changed to meet the different driving load
conditions.
NOTE: The 350C transmission has been replaced in production
with the 400 Series transmission, effective
1986 on G-Series vehicles.
MODELS 350C AND 400-475 SERIES
Chevrolet motor homes are equipped with one of two
different automatic transmissions, the 350C (G-Series)
and the 400-475 (P-Series). Both are fully automatic units
which use a three-element hydraulic torque converter.
The 350 automatic transmission, in addition to the torque
converter, uses two planetary gear sets. Four multipledisc
clutches, two roller clutches, and an intermediate
overrun provide the friction elements required to obtain
the desired function of the two planetary gear sets.
The 400-475 automatic transmission uses a compound
planetary gear set along with the torque converter. Three
Figure 8-1 -Automatic Transmission -Typical
SECTION 8 - TRANSMISSION
TRANSMISSION
multiple-disc clutches, one gear unit, one roller clutch, and
two bands provide the friction elements required to obtain
the desired function of the compound planetary gear set.
The three-element torque converter consists of a pump
or driving member, a turbine or driven member, and a
stator assembly. It is filled with fluid and is attached to the
engine crankshaft at the flywheel (or flexplate). The torque
converter, which always rotates at engine speed, couples
the engine to the planetary gears through the fluid and
provides hydraulic torque multiplication when required .
Automatic transmissions replace the standard clutch and
transmission . After starting the engine with the selector
lever in "P" (Park) or ";N" (Neutral) position, select the
range desired and press the accelerator. All automatic
transmissions are equipped with a starter safety switch ,
designed to permit starting the engine only when the transmission
selector is in the "P" or "N" position. For additional
engine braking effect, as is sometimes needed in mountainous
driving, place the transmission in a low range
(LOW 1 or LOW 2) .
LOW 2 - This range is used when extra performance is
required for hill climbing or it can also be used to provide
"engine braking" to slow the vehicle when going down
medium grades. The shift lever may be moved from "D"
to "2" (and vice versa) under most driving conditions.
TRANSMISSION
ASSEMBLY
LEVER
(MANUAL LINKAGE
CONTROL)
DETENT
VALVE/SOLENOID
LOW 1 - This position is used to provide maximum engine
braking when driving down very sharp grades or
when maximum performance is required to climb a steep
hill or run through deep snow or mud. You may shift into
"1 " at any speed but the transmission will not go into LOW
until vehicle speed is under approximately 40 MPH.
CAUTION: TO REDUCE THE RISK OF PERSONAL INJURY,
BEFORE GOING DOWN A STEEP OR LONG
GRADE REDUCE SPEED AND SHIFT THE TRANSMISSION
TO A LOWER GEAR. DO NOT HOLD THE BRAKE
PEDAL DOWN TOO LONG OR TOO OFTEN WHILE
GOING DOWNHILL . THIS COULD CAUSE THE
BRAKES TO GET HOT AND NOT WORK AS WELL. AS
A RESULT, THE VEHICLE WILL NOT SLOW DOWN AT
THE USUAL RATE. FAILURE TO TAKE THESE STEPS
COULD RESULT IN LOSS OF VEHICLE CONTROL.
TORQUE CONVERTER CLUTCH
A torque converter clutch assembly is also used on some
models. The converter clutch is splined to the turbine assembly,
and when operated, applies against the converter
cover providing. a mechanical direct drive coupling of the
engine to the planetary gears. Converter clutch operation
is determined by a series of controls and by drive range
selection . The transmission must be in drive range, and
the vehicle must have obtained a preset speed depending
on the engine and transmission combination.
Aside from the torque converter, the hydraulic system
within the transmission is pressurized by a gear-type
pump and provides the working pressure required to operate
the friction elements and automatic controls.
CONTROLS
For proper operation of the transmission, certain controls
from outside of the transmission are required. These
include :
1 . Manual Linkage - To select the desired operating
range,
2. Engine Vacuum -To operate the vacuum modulator .
3. Downshift Control -
" Cable to operate the detent valve (350C).
" Electrical circuit to operate the detent solenoid (400-
475 Series) .
MANUAL LINKAGE
The manual linkage is connected between the selector
lever on the steering column, and the transmission . It is
through this linkage that the vehicle driver can control the
transmission operating range.
SECTION 8 - TRANSMISSION
8-2
VACUUM MODULATOR SYSTEM
A vacuum modulator is used to automatically sense any
change in torque input to the transmission . The vacuum
modulator transmits this signal to the pressure regulator,
which controls line pressure, so that all torque requirements
of the transmission are met and smooth shifts are
obtained at all throttle openings.
DOWNSHIFT (DETENT) CABLE SYSTEM -
350C TRANSMISSION - G-SERIES
The detent valve is activated by the downshift (detent)
cable which is connected to the carburetor linkage . When
the throttle is half open, the detent valve is actuated, causing
a part throttle downshift at speeds below 50 MPH .
When the throttle is fully opened, the detent valve is
actuated causing the transmission to downshift. The
3-1 detent downshift may be obtained when vehicle speed
is approximately 6 to 12 MPH below the maximum throttle
1-2 upshift point. The 3-2 detent downshift may be obtained
when vehicle speed is,approximately 4 to 8 MPH
below the maximum throttle 2-3 upshift point.
DETENT DOWNSHIFT ELECTRICAL
CIRCUIT-400-475 SERIES TRANSMISSION
The detent solenoid is activated by an electric switch on
the accelerator linkage . When the throttle is fully opened,
the switch is closed, activating the detent solenoid and
causing the transmission to downshift for passing speeds .
The switch has a two-wire connector and is mounted on
a metal bracket under the dashboard to the left of the
steering column above the driver's left foot. (Figure 8-2
shows a typical detent downshift switch except the switch
has been rotated 90 degrees counterclockwise to allow a
better view of the activating plunger.)
A- Plunger
B- Cente Side
C - 2-Wire
Connector P-SERIES
Switch rotated 90°
Counterclockwise
Figure 8-2- Detent Switch (THM 400-475 Series)
To adjust the switch :
1 . Preset the switch by pressing the plunger and/or movable
plastic center slide downward as far as possible .
In the preset position, the movable plastic center slide
of the switch will snap down out of position and the
center slide will be nearly flush with the top of the
switch . Check the portion of the slide protruding from
the bottom of the switch . The slide should extend approximately
1-1/4 inches in the reset position.
2. Press the accelerator pedal down to the "wide open"
throttle position and the switch will "self-adjust" by
snapping back into position. When adjusted, the center
slide will be visually protruding out of the top of the
switch (more than 1-1/4 inches as in Step 1).
The switch has been designed so that the switch contacts
close (make contact) when the accelerator pedal is at or
nearly at the floor. If the switch contacts do not close, too
much carpet padding may have been installed by the RV
manufacturer preventing the pedal from reaching the floor
allowing the switch contacts to close.
Disconnect the two-wire connector and check if the contacts
close at "wide-open throttle." Use an ohmmeter or
continuity checker. With the continuity checker or ohm
meter in position, depress the accelerator to the floor (with
the engine off) to verify proper switch operation. If the
contacts do not close, check to see if too much padding
has been installed. Either remove the excess carpet padding
or "build up" the diameter of the switch plunger. To
"build up" the diameter of the switch plunger (allowing
additional switch movement), install a piece of scrap 3/8-
inch hose over the switch plunger. If the switch contacts
still do not close, replace the switch (GM Part No.
1242101) . Recheck and install the two-wire connector.
MAINTENANCE AND INSPECTION
The automatic transmission fluid level should be checked
regularly (at each engine oil change) and changed at the
intervals recommended in the Maintenance Schedule for
your vehicle. Typically, the recommended interval for
changing the fluid and service screen is every 24,000
miles (Heavy-Duty Emissions equipped vehicles) or every
12,000 miles if the vehicle was subjected to severe use.
In addition, the fluid cooler lines, electrical lines, vacuum
lines, control linkage and transmission should be checked
periodically for leaks, damage or deterioration .
NOTE: Transmission conditions can be the result of poor
engine performance. If the engine - requires a
tune-up, this should be done before checking the
transmission .
SECTION 8-TRANSMISSION
FLUID LEVEL AND APPEARANCE
When checking the fluid level, follow the appropriate procedure
listed below. It is also important to know what
appearance the fluid should have. Many times a transmission
malfunction can be traced to an incorrect fluid
level or improper reading of the dipstick . Afluid level which
is too high or too low can cause overheating and clutch
plate damage. In addition, overheating can be caused by
excessive clutch plate slippage which can result from improperly
installed plates, an out-of-adjustment selector
linkage or the manner in which the vehicle is operated.
The type of transmission fluid that is now being used may
appear to be darker and have a stronger odor. This is
normal, and not a positive sign of required maintenance
or transmission failure.
When the dipstick is removed, note whether the fluid is
devoid of air bubbles or not. Fluid with air bubbles is an
indication of an air leak in the suction lines, which can
cause erratic operation and slippage. Water or ethylene
glycol antifreeze in the fluid gives a milky, gray or pink
cast to the fluid and can cause spewing of fluid from the
transmission breather . Coolant in the fluid, whether water
or antifreeze, can cause damage to the nylon parts or
clutch plates in the transmission . If the fluid becomes contaminated
with coolant, the most common cause is a leaking
transmission cooler core. In addition to finding and
fixing the leak, the transmission should be disassembled,
cleaned and the clutch plates replaced with new ones.
Glycol test kits on the market can be used to detect
antifreeze in the transmission fluid. While generally reliable,
certain kits may produce positive test results because
of additives used in some transmission fluids . The
kit manufacturer's instructions should be followed closely.
Capacity
The fluid capacities of both transmissions are listed in the
Lubrication section of this manual . To bring-fluid level from
"ADD" mark to "FULL" mark requires one pint of fluid.
Fluid level should be checked at every engine oil change .
Fluid level should be at the "FULL" mark with transmission
fluid at normal operating temperature of 180°F. With fluid
at room temperature, 70°F, level will be between the two
dimples on the dipstick . The normal operating temperature
is obtained only after at least 15 miles of highway-type
driving. (See Figure 8-3.)
COOL HOT
(65*-85*F) (180°F)
ADD 5 LITER
(1 PT) O
WARM
FULL HOT
NOTE: DO NOT OVERFILL. IT TAKES
ONLY ONE PINT TO RAISE LEVEL
FROM "ADD" TO "FILL" WITH A HOT
TRANSMISSION .
Figure 8-3- Transmission Dipstick-Fluid Levels
at Varying Temperatures
Checking and Adding Fluid
TRANSMISSION AT OPERATING TEMPERATUREThe
automatic transmission is designed to operate at the
"FULL HOT" mark on the dipstick at normal operating
temperatures of about 180°F and should be checked under
these conditions. The normal operating temperature
is obtained only after at least 15 miles of highway-type
driving .
CAUTION : WITH NORMAL OPERATING TEMPERATURES,
THE DIPSTICK WILL BE EXTREMELY HOT TO
TOUCH . USE CARE TO AVOID BURNS.
To determine proper level, proceed as follows :
1 . Apply the parking brake and block the vehicle wheels.
2.. With the selector level in the PARK position, start the
engine. DO NOT RACE ENGINE. Move the selector
lever through each range.
3. Immediately check the fluid with the selector lever in
PARK, engine running at SLOW IDLE and the car on
a LEVEL surface . The fluid level on the dipstick should
be at the "FULL HOT" mark.
4. If additional fluid is required, add sufficient fluid to bring
the level to the "FULL HOT" mark on the dipstick .
TRANSMISSION AT ROOM TEMPERATURE (65° to
85°F) - Automatic transmissions are frequently overfilled
because the fluid level is checked when the fluid is cold
and the dipstick indicates fluid should be added. However,
the low reading is normal since the level will, rise as the
fluid temperature increases (Figure 8-3). A level change
of over 3/4 inch will occur as fluid temperature' rises from
600 to 180*F.
Overfilling can cause foaming and loss of fluid through
the vent. With too much fluid, the rotating members churn
SECTION 8-TRANSMISSION
8-4
the fluid, producing aeration which reduces the fluid's
cooling effectiveness . Slippage and transmission failure
can result.
Fluid level that is too low can result in transmission charging
pump cavitation, a loss of main and lubrication fluid
pressure and clutch plate damage . It can cause slipping,
particularly when the transmission is cold or the vehicle
is on a hill .
Check the transmission fluid level with the engine running,
the shift lever in PARK, and the vehicle level.
If the vehicle has recently been operated for an extended
period at high speed or in city traffic in hot weather or the
vehicle is being used to pull a trailer, an accurate fluid
level cannot be determined until the fluid has cooled down,
usually about` 30 minutes after the vehicle has been
parked .
Remove the dipstick and touch the transmission end of
the dipstick cautiously to find out if the fluid is cool, warm
or hot.
Wipe the dipstick clean and reinsert it until the cap seats.
Remove the dipstick and note reading .
1 . If the fluid feels cool, about room temperature (65°-
85°F), the level should be between the two dimples
below the "ADD" mark.
2 . If it feels warm, the level should be close to the "ADD"
mark (either above or below).
3. If it feels hot (cannot be held comfortably), the level
should be between the "ADD" and "FULL" marks.
Changing Fluid
1 . Raise the vehicle .
2. With a drain pan placed under the transmission pan,
remove the pan attaching bolts from the front and
side of the pan.
3. Loosen pan rear attaching bolts approximately four
(4) turns.
4. Carefully pry the transmission pan loose, allowing the
fluid to drain .
. Remove the remaining bolts and remove the pan and
gasket.
6. Drain the fluid from the pan . Clean the pan with solvent
and dry thoroughly with clean compressed air.
7. Remove screen/filter and gasket.
8 . Paper or felt-type filters should be replaced .
9. Install, as required, a new gasket or O-ring onto the
screen/filter assembly. Lubricate 0-rings with
petrolatum.
10. Install a new gasket on the pan and install the pan.
Torque the attaching bolts to 13 ft. lbs. (350C transmission),
12 ft. lbs. (400-475 transmission) .
11 . Lower the vehicle and add- the proper amount of
DEXRON IIE® automatic transmission fluid through
the filler tube.
12. With the selector lever in PARK position, apply the
parking brake, start the engine and let idle (carburetor
off fast idle step) . DO NOT RACE ENGINE.
13. Move the selector lever through each range and, with
the selector lever in PARK range, check fluid level.
14. Add additional fluid to bring the level between the
dimples on the dipstick (cool level) .
AUTOMATIC TRANSMISSION MANUAL
LINKAGE
When the manual linkage (Figure 8-4) is properly adjusted,
the engine will start in the PARK and NEUTRAL
positions only.
The selector lever and manual linkage should move freely
and not bind. Also, the pointer on the indicator quadrant
should line up properly with the range indicators in all
ranges.
Check the linkage to be sure that the connections are
secure and that there is no binding . If there are indications
that the linkage needs adjustment, take the vehicle to a
qualified shop for service . If the linkage is not adjusted
properly, an internal leak could occur at the manual valve
which could cause a clutch and/or band failure .
COOLER LINES
If replacement of transmission steel tubing cooler lines
(Figure 8-5) is required, use only wrapped and brazed
steel tubing meeting GM specifications 123M or equiva-
,lent. DO NOT USE COPPER OR ALUMINUM TUBING
TO REPLACE STEEL TUBING. These materials do not
have satisfactory fatigue durability to withstand normal
vehicle vibrations. Steel tubing should be flared using the
double flare method.
TRANSMISSION MOUNT
SECTION 8
A loose transmission mount can cause a vibration in the
driveline . To check for this condition, push up and pull
down on transmission tailshaft while observing the transmission
mount. If rubber separates from the metal plate
of the mount or if the tailshaft moves up but not down
(mount bottomed out), replace the mount. If there is relative
movement between a metal plate of the mount and
its attaching point, tighten the screws or nuts attaching
the mount to the transmission or cross member (Figure
8-1).
TRANSMISSION SHIFTING
If problems are encountered with the transmission shifting
(upshift or downshift), refer to the appropriate shop manual
for the diagnosis and adjustment procedures, or take
the vehicle to a qualified service shop.
TRANSMISSION
SELECTOR LEVER
RETAINER
ROD
SWIVEL
FRAME ASSEMBLY
SPRING WASHER
SCREW
CROSS SHAFT
NOTE: 1991-94 uses a cable shift.
Figure 8-4-Transmission Manual Linkage-Typical
TRANSMISSION
PIPE
OUTLET
FRONT
INLET
COOLER LINES PIPE
ENGINE
RADIATOR
NOTE: Depending on model year, cooler lines
will enter the radiator from the left or the
right side.
Figure 8-5 - Automatic Transmission
Cooler Lines-Typical
1 . Remove the flywheel cover.
SECTION 8
ENGINE/TRANSMISSION TORQUE
CONVERTER/CLUTCH BALANCING
The engine, torque converter, clutch cover or flywheel are
balanced individually and are normally good for the life of
the vehicle . Occasionally two or more components can
be assembled with an imbalance problem and actually
end up "working against each other" to create a lessthan-
desirable running condition . Or, a vehicle may be
acceptable as produced, but after the clutch or transmission
has been repaired a vibration may surface . This is
especially true with some used or non-GM rebuilt parts.
An engine balance problem may exist if the vibration is
present at a given engine RPM with the transmission in
NEUTRAL and the wheels are not turning .
If diagnosis indicates that there is an engine and/or flywheel
torque converter imbalance problem, the engine
and torque converter can be balanced in the vehicle using
the following procedure .
If the engine is equipped with an automatic transmission :
2. Reposition the converter in each attaching position on
the flywheel and evaluate the vibration in each position .
If there is no reduction in vibration, proceed to Step 3.
3. Remove a converter to flywheel bolt and add balance
weight by installing a longer bolt with several flat washers
under the head of the bolt. Determine ifthe vibration
is more or less severe. The vibration should be appraised
by moving the longer bolt and washers to each
position possible.
4. Install the bolt and washers in the position which creates
a properly balanced situation .
NOTE : It may be necessary to divide the weight between
two adjacent bolts on the torque converter to obtain
a proper balance.
If the vehicle is equipped with a manual transmission :
1 . Place the transmission in NEUTRAL with the clutch
engaged and increase the engine speed between
1,000 and 3,000 RPM . Note the degree of imbalance
that occurs.
2. Place the transmission in gear with the clutch disengaged
and increase the engine speed between 1,000
and 3,000 RPM. Note the degree of imbalance that
occurs and compare it to the vibration which was determined
in Step 1 above.
TRANSMISSION
3. If a degree of imbalance is noted between Step 1 and
Step 2, the clutch disc is probably causing the problem
and should be replaced before proceeding. If no
difference in imbalance is noted, install flat washers
under the clutch pressure plate hold down-bolt
following the procedure outlined in Step 3 above for
the automatic transmission .
NOTE: If a strobe is available, follow the same general
approach as outlined in the Driveline Balance
Procedure section of this manual . Position the
pickup against the engine oil pan.
ELECTRIC SPEEDOMETER 1991-94
The electromechanical speedometer replaces the
cable driven speedometer on P - models. Components
of the speedometer system includes the
speedometer head, vehicle speed sensor (VSS),
digital ratio adaptor controller, and the applicable
wiring .
The speedometer head is an electromechanical
device using integrated circuits that control the air
core speedometer and stepper motor odometer.
The vehicle speed sensor is a permanent magnet
signal generator located on the transmission output
shaft. This analog signal, which is proportional to
output shaft speed, is sent to the digital ratio adaptor
controller.
The digital ratio adaptor controller (DRAC) is a solid
state devoce which changes the analog signal supplied
by the VSS to a digital signal. This digital
signal is then fed to the speedometer.
The digital ratio adaptor controller is matched to the
final drive of each vehicle. If the final drive ratio is
changed (including tire size) for any reason, the
DRAC must also be changed to match . This will ensure
accurate speedometer readings. The parts
book lists DRAC's (or Buffers) for a variety of tire
sizes and rear axle ratios . Also, an incorrect DRAC
will affect the Electronic Control Module (ECM), and
the cruise control module.
1991-1994 4L80EHD
Effective with the 1991 model, the Class A motor
home incorporates a 4-speed electronic shift overdrive
transmission .
SECTION 8
THE BENEFITS OF ELECTRONIC
CONTROLS
A TRANSFORMATION IN TRANSMISSION
TECHNOLOGY
In traditional, hydraulically controlled transmissions,
the gear shifts are controlled by the opposing
pressures of hydraulic fluid in a complex system of
spring-loaded valves . In the new, electronically controlled
Hydramatic 41_80-E transmission, gear shift
points and shift feel are determined by electrical
signals sent from the Powertrain Control Module.
The Powertrain Control Module processes data
every 25 milliseconds from sensors based on throttle
position, vehicle speed, gear range, altitude,
temperature, engine load, and other inputs . Using
this data, a signal is transmitted to the valve body
Shift Solenoids, which activate the shift valves for
precise shift execution. Shift points are thus
precisely controlled and are identical from vehicle to
vehicle.
Shift feel is also electronically controlled by the
Powertrain Control Module. It sends signals to the
Force Motor Solenoid, which controls fluid line
pressure and determines how firm the shifts will
feel .
The Powertrain Control Module makes the Hydramatic
41_80-E an "intelligent" transmission which
senses and adapts to changes in altitude, engine
load, and other conditions . Electronic controls also
eliminate the need for governor and modulator
systems, which significantly reduces the
mechanical complexity of the transmission .
GENERAL DESCRIPTION
The HYDRA-MATIC 41_80-E is an electronically controlled
four-speed rear wheel drive automatic
transmission . It consists primarily of a torque converter
and three planetary gearsets. Five multiple
disc clutches, one sprag, two roller clutches, and
two bands provide the friction elements required to
obtain the desired function of the planetary
gearsets. A hydraulic pump and an electronically
controlled valve body is used to operate the various
systems contained within the transmission .
The torque converter contains a pump, a turbine,
and a clutch pressure plate splined to the turbine.
The torque converter acts as a fluid coupling to
smoothly transmit torque from the engine to the
transmission . It also hydraulically provides additional
torque multiplication when required . The
clutch pressure plate, when applied, provides a
TRANSMISSION
mechanical "direct drive" coupling of the engine to
the transmission .
The three planetary gearsets provide the four forward
ratios and reverse. Changing of the gear ratios
is fully automatic, mainly in relation to throttle opening
and vehicle speed .
The Powertrain Control Module (PCM) [or Transmission
Control Module (TCM) on some applications], an
on board computer, receives and processes input signals
from various sensors on the vehicle and delivers
output signals to the solenoids located in the control
valve assembly. The solenoids control the transmission
operating pressures, upshift and downshift patterns
and torque converter clutch (TCC) operation .
Hydra-matic 41_80-E Transmission
Specifications
Transmission Type
41_80-E =,4-Speed,
Longitudinal Mount,
High Torque Capacity,
Electron ical ly' Control led
Automatic Overdrive with Torque Converter Clutch
Assembly
Control Systems '
Shift Pattern - Solenoid Control
Shift'Quality - Force Motors Control
' Torque Converter Clutch - Pulse Width Modulated
Solenoid Control
Transmission Fluid Type
Dexron IIE
7 Position Quadrant
(P,R,N,OD,D,2.1)
Maximum Gross Vehicle Weight
7,484 kg (16,500 lb)
Maximum Gross Combined Vehicle Weight
9,072 kg (20,000 lb)
Transmission Fluid Capacities
Bottom Pan
Removal : 7.31_( 7.7 qt)
Dry: 12.81_ (13.5 qt)
Gear Ratios
1st 2.482
2nd: 1 .482
3rd : 1,000
4th : 0.750
Rev: 2.077
SECTION 8
EXPLANATION OF GEAR RANGES
The transmission can be operated in any one of the
seven different positions shown on the shift quadrant.
P - Park position enables the transmission output
shaft to be locked, preventing the vehicle from rolling
either forward or backward. For safety reasons, the
vehicle parking brake should be used in addition to the
transmission "Park" position . Park position should not
be selected until the vehicle has come to a complete
stop. The engine may be started in the Park position.
R - Reverse enables the vehicle to be operated in a
rearward direction.
N - Neutral position enables the engine to start and
operate without driving the vehicle. If necessary, this
position should be selected to restart the engine while
the vehicle is moving .
r
D - Overdrive range should be used for all normal
driving conditions for maximum efficiency and fuel
economy. Overdrive range allows the transmission to
operate in each of the four forward gear ratios . Downshifts
to a lower gear, or higher gear ratio, are available
for safe passing by depressing the accelerator or by
manually selecting a lower gear with the shift selector.
It is not recommended to operate the transmission in
overdrive range when pulling heavy loads or driving on
extremely hilly terrain . Under such conditions that put
an extra load on the engine, the transmission should
be driven in a lower manual gear selection for maximum
efficiency.
D - Manual Third can be used for conditions where it
may be desirable to use only three gear ratios . These
conditions include towing a trailer and driving on hilly
TRANSMISSION
terrain as described above . This range is also helpful
for engine braking when descending slight grades. Upshifts
and downshifts are, the same as in Overdrive
range for first, second and third gears except that the
transmission will not shift into fourth gear.
2 - Manual Second adds more performance for congested
traffic and hilly terrain . It has the same starting
ratio (first gear) as Manual Third but prevents the
transmission from shifting above second gear. Thus,
Manual Second can be used to retain second gear for
acceleration and engine braking as desired . Manual
Second can be selected at any vehicle speed. If the
transmission is in third or fourth gear when Manual Second
is selected it will immediately shift to second
gear.
1 - Manual First can be selected at any vehicle
speed. If the transmission is in third or fourth gear it
will immediately shift into second gear. When the vehicle
speed slows to below approximately 56 km/h
(35mph) the transmission will then shift into first gear.
This is particularly beneficial for maintaining maximum
engine braking when descending steep grades.
1994 BRAKE/TRANSMISSION SHIFT
INTERLOCK
An improved safety feature inhibits the operator from
moving the shift selector lever and the transmission out of
"Park" unless the brake pedal is depressed. A solenoidactuated
plunger will interface with the steering column
mounted transmission-shift lever which remains in a lockout
position until the vehicle brake is applied. The
solenoid will be energized through the brake switch and
allow the shift lever to move from the park position .
AUTO TRANS SHIFT LEVER & CABLE
INSTALLATION & ADJUSTMENT
1 . With trans selector shaft (A) in Neutral, align slot on
lever ASM (B) with flats on shaft (A) .
2. Push lever ASM (B) on to shaft (A) far enough to
engage retaining nut (C) .
CAUTION : Do not drive lever ASM (B) on to trans
selector shaft (A) by hammering or bumping, as internal
components of transmission will be damaged.
3. Hold lever ASM (B) & hand tighten retaining nut (C) to
20-27 N"m torque.
CAUTION : Do not apply torque in excess of 27 N"m,
as damage to selector shaft may occur.
4. Move lever ASM (B) (selector shaft) by hand through
detent range positions to check for freedom from binding
& positive detent engagement.
SECTIONS-TRANSMISSION
BOLT/SCREW
COTTER PIN--/ `WASHER
ADJUSTMENT AT STEERING COLUMN
-C7P
BUSHING E
CABLE ASH F
ADJUSTMENT AT TRANSMISSION
ADJUSTMENT AT STEERING COLUMN
& C7P
BUSHING E
CABLE ASH F
BOLT/SCREW
TRANSMISSION SHIFT CABLE
1991-1994
Part #156443445
5. With steering column shift lever in neutral attach link
(D), bushing (E) & cable ASM (F) as shown.
6. With trans lever ASM (B) in neutral position install and
adjust clevis (G) for free pin (H).
7. Install clevis pin (H) & secure with cotter pin (J).
8. By moving steering column shift lever through full
range check for positive detent engagement at trans
for each position .
9. Readjust clevis (G) if necessary, for positive detent
engagement.
NOTE: Do not use trans cable adjustment to adjust
PRNDL alignment (see UPC 9A/07-04-03 for
PRNDL asjustment procedure).
TRANSMISSION FLUIDS AND
COOLER TIPS
OIL TEMPERATURE MEASURED AT
CONVERTER OUTLET TO COOLER
350°F is the maximum temperature. This is the normal
place to install a temperature gage or signal . The temperature
in this location will vary significantly with each
vehicle start-up or hill. If the temperature reaches 350°F,
reduce throttle. To lower the transmission temperature
with the transmission in NEUTRAL, run the engine at
1,200 RPM for 2-3 minutes to cool the oil . Do not allow
the converter outlet temperature to exceed 350°F. Keep
a close check to prevent the engine cooling system from
overheating . 350°F or higher would be typical of rocking
the vehicle in mud, snow, or sand, or a transmission in
stall (full throttle, no vehicle movement) . When the transmission
is in stall, the transmission will develop heat at a
rate of one degree per second of stall.
OIL TEMPERATURES MEASURED IN THE
SUMP OR OIL PAN
150°F - Minimum operating temperature for continuous
operation. It is possible in low ambient temperature to
overcool the transmission with oil to air-type coolers ; it is
hard to overcool if used in conjunction with oil to water
coolers installed in most standard automotive radiators .
190°-200°F- Proper oil level checking temperature.
200°F - Maximum oil level checking temperature. Beyond
this, readings are not reliable because of expansion .
285°F - Maximum sump/oil pan temperatures for short
duration, such as a long hill climb.
300°F- Metal parts inside the transmission begin to warp
and distort in varying degrees, seals melt rapidly, and
transmission fluid life is extremely short due to oxidation
and distress .
AUTOMATIC TRANSMISSION FLUID
OXIDATION
Automatic transmission fluid can provide up to 100,000
miles of service before oxidation occurs under normal
operating temperaturesof about 170°F. Above normal operating
temperatures, the oxidation rate doubles (useful
life of the fluid is cut in half) with each 20 degree increase
in temperature.
The approximate life expectancy at various temperatures
is as follows :
APPENDIX 8-1
Figure A8-1-1 -Transmission Fluid-
Life Expectancy/Temperature
Relationship
This information shows why the various maintenance
change intervals and/or oil coolers are recommended for
severe usage.
NOTE : THE ABOVE' CHART IS BASED ON THE ASSUMPTION
THAT OIL TEMPERATURE REMAINS
CONSTANT FOR THE MILES
INDICATED. TEMPERATURES WHICH APPEAR
FOR SHORT PERIODS, SUCH AS
CLIMBING HILLS, ETC., WOULD NEED TO BE
AVERAGED AGAINST NORMAL OPERATING
TEMPERATURES TO DETERMINE ACTUAL
LIFE EXPECTANCY.
AUTOMATIC TRANSMISSION FAILURE
IMMEDIATELY AFTER SERVICING
If there was no known prior abuse, the new transmission
fluid is not at fault. What has probably happened is that
a certain amount of highly oxidized fluid remained in the
transmission converter and cooler lines. The old fluid and
new fluid will not mix. They settle out as sludge or varnish,
causing valves to stick and/or plug oil passages and
screens. When this happens, the transmission may malfunction
or fail completely. The best way to prevent the
problem is to follow the manufacturer's drain intervals for
severe operating conditions such as trailer towing, mountain
driving, and stop-and-go city driving .
DEGREES F MILES
175 100,000
195 50,000
212 25,000
235 12,000
255 6,000
275 3,000
295 1,500
315 750
335 325
355 160
375 80
390 40
415 Less than 30 Minutes
TRANSMISSION FLUIDS AND
COOLER TIPS (Cont'd)
AUTOMATIC TRANSMISSION FAILURE
IMMEDIATELY AFTER OVERHAUL
Assuming proper workmanship and assembly, failure can
often be caused by metal particles or debris trapped in
the cooler circuit . Unless the converter, cooler, and cooler
lines are thoroughly flushed during overhaul, the leftover
contaminants will return through the cooler return lines to
the transmission lube supply and may cause a second
failure . To prevent this, be certain all the transmission
components, cooler lines, and cooler are cleaned prior to
reassembly. DO NOT TAKE SHORTCUTS.
DEXRON IIE® VERSUS TYPE F
TRANSMISSION FLUID
Type F fluid must never be used where Dexron II® is
specified . The difference in the fluids relates to their friction
properties. GM transmissions are designed to shift smoothly
which requires a low-static fluid such as Dexron IIE®. On
the other hand, transmissions that require Type F transmission
fluid are designed to shift more harshly, providing
more shift feel. Type F fluid is a highly static fluid, . and
provides more friction than Dexron IIE®. If Type F fluid is
used in a GM-designed transmission, shifting will become
more harsh. In turn, harsh shifts apply higher shock loads
to components that weren't designed for high-shock loads,
and transmission failure is almost certain .
DEXRON IIE ® FLUID COLOR CHANGE AND
STRONG ODOR
These two "tests" are no longer satisfactory criteria for
recommending a fluid drain and refill . With the Dexron II©
Figure A8-1-2- Deaeration Cooling System
APPENDIX 8.1
8-10
fluid, rapid loss of the red color and darkening of the new
fluids are normal and DO NOT affect their performance.
Contrary to past performance, the service technician
should not consider a dark appearance or burnt odor
as the signal to change fluid. The only accurate method
for determining a fluid's serviceability or effectiveness is
through a laboratory analysis . Short of a laboratory analysis
the owner's manual drain recommendation should be
followed.
INSTALLATION OF A MANUAL WATER
SHUT-OFF VALVE IN THE HEATER LINE
DO NOT install a manual water shut-off valve in the heater
line. The heater water return is routed to the radiator outlet
tank and continuous coolant flow is necessary to control
oil temperatures during closed thermostat (warm-up) operation
. (See Figure A8-1-2.) Shutting off this portion of
the heater flow destroys the engine's deaeration system
and may result in premature engine or transmission failure.
A transmission warms ;up faster than the engine and
it is not advisable to have the radiator transmission oil
cooler exposed to air. A bubble cavitating in the engine
water pump could cause engine hot spots. A water shutoff
valve is permissible in the rear seat heater line.
ADDING AN EXTERNAL FLUID COOLER
Before adding an external fluid cooler consideration
should be given to many factors :
" Initial cost
" Need
" Potential extra leak points (For example: A tee added
into the line is not one leak potential but three. A coupling
provides two leak point possibilities -the cooler
has two ends plus the cooler itself .)
" Lines, have potential for fatigue and rubbing or chafing
" Quality of the installation .
The transmission dipstick itself might be considered a
major factor for adding an external cooler. Current dipsticks
have several dots at the low end of the operating
range that would show a ,valid fluid level if checked cool
at 65°-85°F . (See Figure A8-1-3.) This low reading is normal
since the level Will rise as the fluid temperature increases.
A level change of over 3/4 inch will occur as fluid
temperature rises from 60° to 180°F. If starting with the
lower dot and, after driving, the level did not go over the
maximum high of the hash marks, an extra cooler would
be difficult to justify . For this condition, all that's needed
is to consider fluid and filter change intervals per the owner's
manual dealing with severity of service . If in doubt,
change the fluid and filter . If after heavy driving or trailer
pulling,the fluid level rises above the hash marks, an external
cooler may remove enough. extra heat to help stay
within the operating hash marks. (See Figure A8=1-3 .)
COOL HOT
WARM
NOTE: DO NOT OVERFILL. IT TAKES ONLY ONE
PINT TO RAISE LEVEL FROM "ADD" TO
"FULL" WITH A HOT TRANSMISSION .
Figure A8-1-3-Fluid Levels at Varying Temperatures
Figure A8-1-4-Typical Oil Cooler Lines
APPENDIX 8.1
TRANSMISSION FLUIDS AND
COOLER TIPS (Cont'd)
Overfilling can cause foaming and loss of fluid through
the vent. With too much fluid, the gearing "churns" the
fluid and produces aeration and foam, and reduces the
fluid's cooling effectiveness . Slippage and clutch failure
often result. A low fluid level can result in causing pump
cavitation and loss of main and lubrication oil pressures .
This can result in slipping and clutch damage, particularly
when cold or when on a hill.
TRANSMISSION
FRONT
FLUID COOLER LINES
NOTE: DEPENDING ON MODEL YEAR, COOLER LINES WILL ENTER
THE RADIATOR FROM THE LEFT OR THE RIGHT SIDE.
NOTE: After-market transmission temperature gage should be installed in the lower (hot) oil line as viewed from
entering the radiator .
After-market external oil to air cooler should be installed after the GM transmission cooler. The,lower (hot) line should
go first into the lower fitting of the GM radiator cooler then out from the top fitting to the after-market oil to air cooler.
Extreme cold weather may require the after-market oil to air cooler be covered so not to cool the oil to much .
After-market external filter should be installed in the lower (hot) oil line to prevent any debris from reaching the radiator
cooler if the filter is being installed in conjunction with a transmission failure or overhaul .
With fluid coolers, the hot oil enters the bottom of the
cooler and the cooled fluid exits out of the top of the cooler
for better heat dissipation . This is the reverse of the engine
radiator . (See Figure A8-1-4.)
TEMPERATURE MONITORS
The following information has been provided as an aid to
the motor home owner. Features, specifications and
ordering information have been provided.
Tempilabels temperature monitors are extremely useful
in monitoring the safe operating temperature of equipment
such as gear boxes, transmission pans; radiators, the
engine oil pan, heat exchangers, etc . Tempilabels are selfadhesive
temperature monitors consisting of one or more
heat-sensitive indicators sealed under transparent heatresistant
"windows." (See Figure A8-2-1 .)
The centers of the indicator circles turn black at the temperature
rating shown on the label. The color changes
are irreversible and provide a temperature history of the
surface being monitored . The Tempilabel can be removed
and attached to a service record to provide a permanent
service history .
Series AA/4A/4B/4C-Tempilabel®
NOTE: ACTUAL DIMENSIONS ARE
1-3/4-INCHES LONG AND
7/8-INCH HIGH.
THE INDICATING WINDOW IS
7/32-INCH IN DIAMETER. .
Figure A8-2-1- Typical Tempilabel Series
APPENDIX 8-2
The Tempilabel temperature monitor indicates a specific
temperature or sequence of temperatures with a tolerance
of one percent of the respective rating (plus or minus) .
The performance of the Tempilabel temperature monitor
is not affected by transient contact with contaminants such
as solvents, gasoline, fuel oil, lubricants, hot water or
steam.
To use the Tempilabel, remove the film backing to expose
the adhesive. Press the Tempilabel firmly to the desired
work surface . No special treatment to the work surface is
necessary although it should be clean to obtain maximum_
contact and adhesion.
Sample of product and listing of one of several series
available is shown as Figure A8-2-1 . Tempilabels are sold
at nominal cost for a minimum order of 10.
FOR FURTHER INFORMATION:
TEMPIL COMPANY
HAMILTON BOULEVARD
SOUTH PLAINFIELD, NEW JERSEY
07080
(201)757-8300
Part No. Temperature Ratings
4A-100 100 110 120 130°F
4A-110 110 120 130 140
4A-120 120 130 140 150
4A-130 130 140 150 160
4A-140 140 150 160 170
4A-150 150 160 170 180
4A-160 160 170 180 190
4A-170 170 180 190 200
4A-180 180 190 200 210
4A-190 190 200 210 220
4A-200 200 210 220 230
4A-210 210 220 230 240
4A-220 220 230 240 250
4A-230 230 240 250 260
4A-240 240 250 260 270
4A-250 250 260 270 280
4A-260 260 270 280 290
4A-270 270 280 290 300
Geared road speed is the maximum theoretical speed of or may not have enough horsepower to attain this speed.
a vehicle based on engine RPM, transmission and axle To determine geared road speed the formula is as follows :
gear ratios, and tire size. In actual use the vehicle may
GEARED ROAD SPEED = RPM x 60
R x, M
RPM = Engine speed at selected Net Horsepower. (To determine
RPM where maximum horsepower is developed .)
R = Ratio. Transmission gear x axle ratio = R
M = Tire revolutions per mile.
Example : A truck with 8-19.5 tires (613 revolutions per mile). 5.83 axle ratio, 4.8 liter (292) engine (3,400
RPM)
3,400 x 60 = 204,000 = 57 MPH
5.83 x 613 3,574
maximum geared road speed use engine
NOTE: See the Wheel and Tire section of this manual for
typical motor home tire revolutions per mile.
Nonlisted tire size revolutions per mile can be obtained
from local tire dealer catalogs.
Figure A8-3-1
GEARED ROAD SPEED
DETERMINATION
NOTE : Typical class A motor home will be equipped with
a model 475 transmission . Typical Class C will be
equipped with a 350 transmission thru 1990-1991
up both will have the 4L80E transmission .
As shown in the above chart, the breakaway ratio includes
the transmission torque converter ratio. For example: In
the 475 transmission, the mechanical first speed gearing
is 2.48 to 1 times the torque multiplication of the torque
converter ratio of 2.20 to 1, which equals the breakaway
ratio of 5.46 . Breakaway is shown in third gear primarily
to show converter ratio. Third gear at normal road speeds
can be considered a 1 to 1 ratio.
NOTE: For best engine life and economy, an engine
should cruise at a continuous 80 to 90 percent of
rated RPM. Shift points at rated RPM are acceptable.
(See Figure A8-3-2.)
APPENDIX 8-3
8-13
Figure A8-3-2 - Engine Speed vs. Rated
Life Expectancy
AUTOMATIC
Model & 350 400 475 700R4 41_80E
RPO Number MXI MXI MXI MXI
Torque Lock- Break- Lock- Break- Lock- Break- Lock- Break- Lock- Break-
Converter up away up away up away up away up away
First 2.52 5.29 2.48 5.70 2.48 5.46 3.06 6.73 5.21 2.48
Second 1 .52 3.19 1 .48 3.40 1 .48 3.26 1 .63 3.58 3.11 1 .48
Gear Third 1 .00 2.10 1 .00 2.30 1 .00 2.20 1 .00 2.20 2.10 1 .00
Ratios Fourth - - - - - - .70 1 .50 1 .58 0.75
Reverse 1 .94 4.07 2.10 4.83 2.10 4.62 ' 2.29 5.03 4:37 2 .08
1 . Jack up a drive wheel on one side of the vehicle . Shift
the transmission into NEUTRAL.
2. Mark the pinion flange or yoke of the drive unit at some
convenient reference point. Mark the tire of the drive
wheel that is off the ground. Turn this drive wheel two
complete revolutions noting the number of revolutions
of the marked pinion flange or yoke. The number of
revolutions of the pinion flange or yoke indicates the
gear ratio of this axle. For example:
Two revolutions of the drive wheel and 7-2/3 (7.66) revolutions
of the flange or yoke mean the gear ratio of this
axle is 7.66 :1 .
APPENDIX 8-4
CHECKING GEAR RATIOS SINGLE
DRIVE AXLES
The method outlined below may be used whenever it is desirable to check or verify the gear ratio of a rear axle .
Two-speed axles may be checked by repeating the procedure in both high and low axle ratios.
When only one drive wheel is free to turn, the action of
the differential gear assembly requires that the drive wheel
be given two complete revolutions to obtain the proper
gear ratio by this method.
You could expect 4.10, 4.56 or 4.88 as typical Class A or
C motor home axle ratios .
NOTE: See the Wheel and Tire section of this manual
for typical motor home tire revolutions per mile.
Non-listed tire size revolutions per mile can be
obtained from local tire dealer catalogs.
APPENDIX A
DRIVE BELTS AND TENSION
SPECIFICATIONS
Proper care and maintenance of drive belts is an important
part of good engine maintenance . Proper belt tension and
the condition of the pulley grooves are of primary concern.
Since belts and pulleys wear with use, look at all frictional
surface areas for signs of wear. Normal wear can be recognized
as even wear, both on the belt and the grooves
of the pulley . It is the unusual signs of wear that indicate
some corrective action is necessary.
When checking; remember that failed or partially failed
belts shown to be defective may have been damaged by
a bad pulley, a misaligned drive or by some faulty mechanical
component .
UNUSUAL WEAR CONDITIONS
VIEW 1
BASE
CRACKING
VIEW 2
FABRIC
RUPTURE
VIEW 3
COVER
TEAR
VIEW 4
SLIP
BURN
VIEW 5
GOUGED
EDGE
VIEW 6
WORN
SIDES
BASE CRACKING
Excessive cross-checking (View 1) extending into the rubber
on the base of a belt and showing little or no side
wear indicates that it must be replaced . Small cracks only
in the cover material do not indicate belt failure.
If the belt fails after three or four seasons of use, the belt
should not be classified as being defective . However, if
the base of the belt also shows cross-checking, the belt
has been exposed to weather to the extent that the inner
fabric is beginning to rot.
FABRIC RUPTURE
A fabric rupture (View 2) can be caused by operating a
belt over a badly worn pulley, by too much tension which
forces the belt down into the groove, or by foreign objects
falling into the pulley groove while the drive is operating .
COVER TEAR
A tear in the cover of a belt (View 3) is normally a result
of the belt accidentally coming into contact with some part
of the application . It is no fault ofthe belt or its construction .
Cover tears are usually caused by belts running too
loosely allowing them to "throw-out" centrifugally and rub
other parts of the application . Proper belt tension will prevent
this from happening.
NOTE : A slight raveling of the belt covering at the splice
location does not indicate imminent belt failure.
Simply cut off loose raveling .
SLIP BURN
This belt (View 4) was ruined by operating too loosely .
The belt slipped under load. And when it finally grabbed,
it snapped .
Proper belt tension would have avoided this failure .
GOUGED EDGE
A gouged edge in a belt (View 5) can be caused by a
damaged pulley or interference with some part of the
application .
Check the condition of the pulley . Make sure the belt does
not rub on any part of the application while operating.
WORN SIDES
Badly worn belt sides (View 6) result from long operation
without enough tension . The sides will be worn and slightly
burned around the entire circumference .
Check for proper belt tension . Also check the pulleys for
incorrect alignment .
ALI
DRIVE BELTS AND TENSION
SPECIFICATIONS (Cont'd)
DEFECTIVE BELTS
EXCESSIVE STRETCH
A belt that stretches excessively is one that stretches
beyond the adjustment provided to take up normal belt
stretch .
LUMPY BELTS
Lumpy belts usually occur and are more noticeable on
variable speed drives and other high-speed belt installations.
The result is excessive vibration . If belts are not
relieved of tension while the engine or vehicle is stored,
they will often cause temporary vibration upon start-up.
Give them time to straighten out .
INTERNAL CORD FAILURE
Failure of one or more of the internal tension cords will
result in the belt rolling out of the pulley groove. Cords
can be broken by prying the belt over the pulley .
IMPROPER LENGTH
It is possible that an improper length belt could accidently
be installed on an engine. Always check to be certain that
the belt length is correct before the belt is installed .
APPENDIX A
A-2
BELT INSTALLATION
Use the following procedure when installing new belts:
1 . Move the belt tension adjustment to the position where
it provides the most slack. In some cases it may be
necessary to remove the accessory to install the belt.
2. Examine pulleys for chips, cracks, bent sidewalls, rust,
corrosion or other damage.
3. Check pulley alignment.
4. Place belts in the pulley grooves by hand.
NOTE: Never pry or force a belt onto the pulley with a
screwdriver,"crowbar, wedge, etc ., since both belt
and drive can be damaged.
BELT REPLACEMENT
Here are a few service tips for replacing belts.
Replace Belts In Matched Sets
Never replace just one belt on a 2-groove, single pulley
setup.
Never install only one belt from a different set of matched
belts. Install a complete, matched belt set .
A.I .R . PUMP
(NA5 ONLY)
BELT LASH-UP CONFIGURATIONS
1985 1/2 - CURRENT
POWER STEERING
PUMP
A.I .R. PUMP
(NA5 ONLY)
A.I .R. PUMP
CRANKSHAFT
3RD TRACK "
454 WITH FACTORY 454 WITHOUT
AIR CONDITIONING AIR CONDITIONING
NOTE: 1990 THRU 1994 - A.I .R . PUMPS WERE ELIMINATED
APPENDIX A
DRIVE BELTS AND TENSION
SPECIFICATIONS (Cont'd)
Check Condition Of Pulleys
Always check the condition of pulleys before replacing
belts. Inspect the pulleys for chips, cracks, bent sidewalls,
rust, corrosion, etc . Replace any pulleys found to be
defective .
Check Pulley Alignment
Misaligned pulleys result in shortened belt life. Check the
alignment between pulleys as follows :
1 . Position a straightedge or cord line to touch both pulleys
at all points . The shafts must be parallel .
2. Rotate each pulley a half revolution and note whether
the contact of either pulley with the straightedge or
cord line is disturbed . If so, this indicates a bent shaft
or warped pulley .
BELT TENSION ADJUSTMENT
To carry their full load, belts must grip the entire area of
contact with the pulley . When operated too loosely, belts
can slip, heat, burn, or grab and snap. More belts fail from
undertightening than from overtightening .
When operated -too tightly, belts can damage the engine
by causing side loading on the crankshaft, crankshaft
bearings, and accessory bearings. Excess tension also
stretches and weakens belts.
Proper Belt Tension (V-Belts) : When installing V-belts,
keep the following in mind :
Adjust the belt tension so that a firm push with the thumb
at a point midway between two pulleys will depress the
belt no more than 1/4 inch (Chevrolet engine) . If a V-belt
tension gage is available, adjust the belt tension as outlined
in the belt tension chart which follows .
NOTE : When installing or adjusting accessory drive
belts, be sure the bolts in the accessory adjusting
pivot point and in the adjusting slot are tightened
properly.
New drive belts will stretch after the first few hours of
operation . Run the engine for 15 second's to seat the belts,
then check belt tension again . Retighten fan drive, pump
drive and battery-charging generator drive belts after 1/2
hour or 15 miles and again after 8 hours or 240 miles of
operation. Thereafter, check the tension of the drive belts
every 200 hours or 6,000 miles and adjust them if necessary.
Belt tension tools are available from several tool
manufacturers, as listed below:
No. BT-7825
Borroughs Tool and Equipment Company
2429 North Burdick Street
Kalamazoo, Michigan 49007-1897
No. 91107
Gates Rubber Company
999 South Broadway
Denver, Colorado 80217
No.J-23600
Kent Moore Tool Division
28635 Mound Road
Warren, Michigan 48092
NOTE: J23600B -
Similar to
Borroughs Gage.
ALL V8 ENGINES EXCEPT DIESEL
Generator 50 Lb. Adjust to 75 ± 5 Lbs . Used
A.I .R . Pump Min . Adjust to 125 ± 5 Lbs. New
P/S Pump
A/C Compressor 65 Lb. Adjust to 95 ± 5 Lbs. Used
Min. Adjust to 140 ± 5 Lbs. New
6.2L - V8 DIESEL
Generator 70 Lb . Adjust to 75 ± 5 Lbs. Used
P/S Pump Min. Adjust to 110-140 Lbs. New
A/C Compressor 80 Lb. Adjust to 90 ± 5 Lbs. Used
Min. Adjust to 135-165 Lbs. New
BELT TENSION CHART
APPLICATION CHART- BELTS & HOSES
for P-30(32) Series Motor Home with 454 CID Engine
Year Remarks GM Part No.
Fan Belt, Generator Belt
Power Steering Pump Belt
A.I.R. Pump Belt
With and Without A/C
All Federal Jobs, Hi Ride
.47 inch x 45.00 inches
GM Code: CNA
19851/2
to
1989
Air Conditioning Belt (GM-ARA)
19851/2
to
Current
DRIVE BELTS AND TENSION
SPECIFICATIONS (Cont'd)
DO NOT USE BELT DRESSING
APPENDIX A
14092344
(Production No.)
10034695
(Service No.)
Hi Ride
3/8 inch x 60.5 inches
GM Code: GA
15598439
(Production No.)
14033869
(Service No.)
Belt dressing is not recommended for belts at any time.
Most dressings contain chemicals which tend to soften
belts . While this softening process does increase the friction
between the belt and pulley grooves, the result is only
temporary.
BELT CLEANING INSTRUCTIONS
Remove all grease and oil as quickly as possible before
they can penetrate the belt and cause deterioration .
A-4
Year Remarks GM Part No.
Radiator Hose
73-81 Upper Hose
Vertical Radiator
350 Engine 6259952
1 1/2 ID Ident 6259952
73-81 Upper Hose
Vertical Radiator
454 Engine 6259953
1 1/2 ID Ident 6259953
1982 Upper Hose
to Horizontal Radiator 14049401
Current 454 Engine 15599363
Varies by Model & Option
1983 Upper Hose
Horizontal Radiator 15595586
1984 6.2 Diesel 14049497
Varies by Model & Option
1985 Upper Hose 14049401
454 Engine H4D
85-89 Upper Hose 15599363
454 Engine H5D
90-94 Upper Hose 15638164
454 Engine H5D
73-81 Lower Hose
Vertical Radiator 350 and
454 Engine 343414
1 3/4 ID Ident 343414
1982 Lower Hose
Horizontal Radiator
350 Engine 343414
Same as 73-81
Vertical Radiator
1982 Lower Hose
to Horizontal Radiator
1984 454 Engine 14049500
1982 Lower Hose
to Horizontal Radiator 15595587
Current 6.2 Diesel 14042372
4.54 Gas 14049500
1979-85 9433752
19851/2 Poly V, 6 Rib 14087540
to 55.98 inches (Production No.
1989 (1422.0 mm) & Service No.)
1990 (1340 mm) 10085787 -
1979-85 Without A/C 9433745
19851/2 Without A/C 14087507
to .47 inch x 45.5 inches (Production No.)
Current 10034695
(Service No.)
19851/2 With A/C, Hi Ride 14082454
to 3/8 inch x 41 inches (Production No.)
Current GM Code: XL 9433735
(Service No.)
Special consideration may be required when conditions
of high humidity, extreme temperatures or outdoor storage
are encountered. Local experience will dictate any Additional
protective measures for such conditions.
" Prior to storage, fill tank/tanks, add fuel stabilizer,
run engine and generator to insure stabilized fuel is
circulated throughout the complete fuel system.
" Keep chassis windows closed. Make sure all covers
are in place.
" Avoid trees in parking area to eliminate potential damage
from tree sap or bird droppings . Remove high weed
growth which affects paint by attracting insects or causing
stains .
" Rinse, wash and wipe horizontal surfaces of motor
home at least once per week when stored outside to
remove accumulations which settle on flat surfaces .
" Leave parking brake in "OFF" position .
" Unit should be parked on level surface or with front of
chassis higher than rear if level surfaces are not available
._ This is to prevent gasoline draining into engine
over a long period causing possible damage to engine
by "hydrostatic lock" when started .
" Check engine coolant and, if necessary, increase
antifreeze.
PREPARING THE MOTOR HOME
FOR STORAGE
Check battery/batteries and inspect test hydrometer on
Delco Freedom or maintenance-free batteries and
charge if green dot is not visible to avoid freezing and
deterioration . Both battery cables should be disconnected
at the battery/batteries to prevent gradual discharge,
and the possibility of fire due to short circuits.
On conventional batteries, check electrolyte specific
gravity and charge if below 1 .255. (See Battery Maintenance
During Vehicle Storage section of this
Appendix.)
Check and secure all caps to prevent water, snow and
dirt from entering engine.
Check and keep tires inflated to recommended tire
pressure.
Remove windshield wiper arms and blades and store
in vehicle .
Start and run engine until completely warm . Drain engine
oil and replace filter element, refill with fresh oil . If
vehicle is equipped with air conditioning, the unit should
be operated during this final engine warm-up to lubricate
compressor seal .
APPENDIX B
Gasoline Engines Only - After the oil has been replaced,
remove air cleaner and pour 1/2 to 1 pint of 10W
or lighter oil into carburetor air intake with engine running .
Pour slowly at first, then rapidly using last quarter to stall
engine. Replace air cleaner .
REACTIVATING VEHICLE AFTER
EXTENDED STORAGE
" Check oil and fluid levels and replenish as necessary
in the following components: engine, radiator, crankcase,
transmission and differential. Check gasoline
supply. If the vehicle is equipped with air conditioning,
refer to the procedure which follows below.
" Check under hood and under vehicle for nesting creatures
and evidence of leakage of oils or fluids or physical
damage.
" Inflate tires to recommended pressure.
Clean battery end of cables and install fully charged
battery .
Lubricate chassis suspension and steering
components.
" Check brake operation and fluid level . Bleed and adjust
brakes if necessary .
Remove spark plugs and clean and gap (gasoline
engines) .
" Check and clean carburetor air filter assembly.
IF VEHICLE IS EQUIPPED WITH AIR
CONDITIONING
" Disconnect the compressor clutch wires before attempting
to start vehicle .
" Check to see if compressor hub and clutch driver can
be turned by hand. If not, the unit should be broken
loose by manually turning the shaft with a wrench on
the shaft lockout on the clutch driver plate. A few "rocking"
turns should be sufficient so that the shaft can be
turned by hand.
*Reconnect coil wires and check belt tension . Run
engine with air conditioning on for a minute or two to
reseal system .
Check the refrigerant . This can be done by checking
for air bubbles in the sight glass on the top of the receiver-
dehydrator (on vehicles so equipped) .
APPENDIX B
PREPARING THE MOTOR HOME
FOR STORAGE (Cont1d)
BATTERY MAINTENANCE DURING VEHICLE
STORAGE
Parasitic loads (drains) from the radio, clock, ECM, courtesy
lights, and other accessories will discharge batteries
in vehicles not used for an extended period of time, or
especially during vehicle storage. Provisions to maintain
a proper state of charge of batteries in these vehicles is
necessary . The discharged batteries can freeze at temperatures
as high as 32°F, resulting in permanent damage.
Other permanent damage may also result to batteries
allowed to stand discharged for extended periods .
To alleviate battery discharge, the negative battery cable
should be disconnected on vehicles which are not going
to be in service within a 20-day period. If this is not possible,
batteries should be checked every 20-45 days, and
recharged if necessary. If the "green dot" of the battery
is not visible, then the battery must be recharged . (Check
the battery maintenance and inspection procedures
information in the Engine Electrical System section of this
manual.)
Disconnected batteries will also self-discharge, especially
in higher ambient temperatures ; therefore, even disconnected
batteries should be checked for a "green dot"
every four months and recharged if necessary.
In addition, any electrical connections or fuses removed
or disconnected to reduce parasitic loads should be reinstalled
or connected prior to reactivating the vehicle after
extended storage.
NOTE: The ignition switch must be OFF when connecting
the battery cables or a battery charger. Failure to
do so may overload or damage the ECM or other
electronic components from voltage spikes which
can occur during these operations.
NUT AND BOLT IDENTIFICATION
The following is presented as an aid to the motor home
owner in understanding some of the problems of threaded
fasteners, as well as to provide information to make better,
safer and more permanent repairs .
" Every mechanic knows from experience that any nut or
bolt can be overtightened to the point of failure. Few
realize that nuts and bolts can also fail or break in
service if not tightened enough.
" Loose nuts result from using the wrong grade bolt as
often as from undertightening.
" In critical applications, standard threaded nuts used
more than once can cause failure of the bolts they are
installed on.
" There is a right way and a wrong way to install a flat
washer on a bolt. An improperly installed flat washer
can cause bolt failure. (See NOTE in Washer Applications
section of this Appendix.)
FORCES ACTING ON NUTS AND BOLTS
To understand some of the problems of threaded fasteners,
it is necessary to understand several factors concerning
the forces that act upon nuts and bolts as well as
the properties of the materials nuts and bolts are made
from.
TENSION - One of the basic forces acting upon a nut
and bolt is tension . Under tension, all grades of steel bolts
will stretch . Up to a point (called the "yield point'), this
stretching is not permanent and the bolt will return to its
original dimensions once the tension has been removed.
If the load is great enough to cause the bolt to stretch
2/10 of one percent of its original length, the stretching
will become permanent.
TENSILE STRENGTH - Once the yield point of a bolt
has been exceeded, the bolt will continue to support
increasing loads but it will also stretch rapidly and
permanently until the tension load equals the tensile
strength. Tensile strength determines the point at which
a bolt will break.
PROOF LOAD - Successful applications of nuts and
bolts are achieved when the tension in the bolt comes as
close as practical to the yield point without exceeding that
point. This tension is called the "proof load"' and is the
maximum load the bolt can support.
TORQUE OR TORSION - It would be extremely convenient
if the tension or clamping force of a bolt could be
measured directly "in the field," however, this direct measurement
cannot be accomplished successfully . The measurement
must be made indirectly using another force that
acts upon nuts and bolts. This force is referred to as
torsion or torque. Torque is the twisting force that is applied
to the nut and bolt during tightening.
APPENDIX C
A-7
When the bearing surfaces of a nut and bolt touch the
workpieces that are being fastened together, friction is
generated in two places; (1 .) at the flanks of the threads
on the bolt and nut and, (2.) at the point of contact of the
nut or bolt head and the workpiece . About 40 percent of
the torque (or twisting force) applied to a nut or bolt being
tightened is expended oveacoming thread friction while 50
percent of the torque input is lost to friction between the
nut and the workpiece . This leaves 10 percent of the
torque applied to new unlubricated nuts and bolts being
available for bolt stretch or clamping force.
WASHER APPLICATIONS
Two of the most important parts of a well-engineered bolt
are the washer face and the fillet where the shank of the
bolt joins the head of the bolt.
WASHER FACE - The washer face is the raised portion
of the head that contacts the workpiece . The washer surface
keeps the hex points of the bolt head from digging
into the workpiece and increasing the installation torque.
This prevents a false torque wrench reading which would
result in an undertightened bolt. The washer surface of
the bolt has the same area as the bearing surface of the
nut so that friction or torque will be equal whether the nut
or bolt is actually being tightened .
FILLET - The fillet is the small radius or curve between
the side of the shank and the washer face of the bolt. The
purpose of the fillet is to reduce concentrations of stress
where the bolt head and the shank of the bolt meet. A
deep "scratch" in the fillet area could weaken the bolt to
the point of causing the bolt head to break off under tension.
One possible cause to this type of problem is the
sharp edge of a drilled hole which digs into the fillet beneath
the bolt head. As the sharp edge digs into the fillet,
a small crack results which progresses to actual bolt failure
when full tension is applied . The solution to this problem
is to protect the fillet either by slightly countersinking
the drilled hole to remove any sharp edge or by using a
flat washer under the bolt head.
NOTE: There is a "right way" as well as a "wrong way"
to install a flat washer. As part of the stamping
process in making flat washers, every washer has
both a "sharp" side and a slightly "rounded" side.
Before using a flat washer, examine the washer
closely to identify which side is sharp and which
is slightly rounded . The rounded side must ALWAYS
be placed next to the bolt head while the
sharp side must be placed against the surface of
the workpiece . Failure to position a washer in this
manner defeats the purpose of the flat washer.
NUT AND BOLT FAILURE
Perhaps the most common cause of bolt failure is the use
of too low a grade of bolt for the application . For example;
a bolt that has a yield strength too low for the forces being
applied will stretch permanently and when the equipment
is shut-down and the load on the bolt relaxes, the result
appears to be a loose nut . A service technician who spots
the loose nut is going to tighten it; however, in this case
tightening the nut and bolt will not solve the problem.
When the equipment is started and the load is reapplied,
the bolt will stretch again. The next time the load relaxes,
the nut will again be loosened . Again the service technician
will tighten the nut although this time the technician
will probably apply additional force. If the bolt breaks, as
it usually does, it is replaced with the same grade of bolt
as the original and the process repeats itself .
There are several ways to avoid this cycle from occuring.
They are:
1 . Drill out the hole and replace the original bolt with one
of the same grade having a larger diameter.
2. Use a higher grade bolt than the original .
3 . In some cases, it may be possible to substitute a finethread
nut and bolt for a coarse-thread nut and bolt of
the same grade and diameter. Fine-thread bolts tend
to be about 10 percent stronger than their coarsethread
counterparts .
Just as important as using the correct grade nut and bolt
for a job is the necessity for the nut, bolt and washer to
be matched to each other. If a low-grade nut is used with
a high-grade bolt, it is very likely that the threads of the
nut will either "strip out or freeze" to the bolt before the
proper torque can be achieved. A soft flat washer used
with a high-strength bolt and matching nut will have a
tendency to compress or "brinnel" under specified torque
settings . This situation reduces the bolt's tension and
makes it subject to fatigue failure. A hardened washer is
heat treated and "file hard."
HEAT-TREATED BOLT - Bolts of Grade 5 and higher
are heat treated for greater strength. When these bolts
are used in areas of vibration, extra care must be taken
to be certain they are properly installed and tightened to
avoid fatigue failure.
If a heat-treated bolt is installed without being tightened
to its design torque (i.e., undertightened), the operational
loads placed on the bolt (vibration, shock or impact) will
exceed the clamping force applied using a wrench. Any
shock or vibrational load above the yield point of the bolt
will cause the bolt to stretch and relax like a spring . Pro-
APPENDIX.C
NUT AND BOLT IDENTIFICATION
(Cont1d)
viding that the stretch does not exceed 2/10 percent of
the grip length of the bolt, the bolt will return to its previous
length when the load is relaxed . However, the ability of
heat-treated bolts to withstand repeated stretching and
relaxing is limited. Continuous stretching of a heat-treated
bolt causes tiny cracks to form at areas where stress is
concentrated. These areas can be at the root of the
threads, at the fillet under the head of the bolt, or anywhere
there is a surface flaw such as a nick or scratch . In time,
these cracks will widen and the bolt will fail.
FATIGUE FAILURES
Bolts must be tightened properly to eliminate repetitive
stretching problems. Correct torque must be applied so
that the clamping force that is generated is greater than
any load the fastened workpieces would be subjected to.
Correct torque ensures that a bolt is properly "preloaded."
A pre-loaded bolt does not continually stretch
and spring back, or is not subject to fatigue and/or failure.
Fatigue failures can also be caused by undertightening or
reusing nuts and bolts in critical applications. The nut is
perhaps the most dangerous fastener to use more than
one time. The reason for this is that standard nuts have
to be made softer than the bolts they match. Failure occurs
because the threads of a new nut become slightly (but
permanently) compressed when tightened the first time.
This is referred to as the nut being "plastically" deformed.
The second time the nut is used, the threads grip the bolt
a little "tighter" using more of the applied torque to overcome
thread friction and less of the torque to clamping
force. Each time the nut is reused it loses more of its
clamping power. The result is the same as an undertightened
assembly even though a service technician
were to follow a torque chart and use a torque wrench.
In some cases, nuts that have been reused as few as five
times have been shown to be capable of only 57 percent
of their original clamping force. Such a loss of pre-load
would not only allow parts to shift out of alignment, it could
also encourage fatigue failure.
In vibration areas, any condition that prevents a bolt from
being properly pre-loaded or that causes the pre-load to
deteriorate will activate fatigue failure . Quite often the initial
tension is lost due to gasket compression, soft washers,
"mushing out," etc .
TORQUE WRENCH APPLICATION
"DO NOT LUBRICATE" should become a common practice
when using a torque wrench and standard torque
tables . All torque chart values are valid only for clean, dry
threads on new nuts and bolts unless otherwise called for
in specific shop manual applications.
APPENDIX C
NUT AND BOLT IDENTIFICATION
(Cont'd)
The reason for this is that any sort of lubrication cuts
thread friction which allows more of the tightening torque
to be converted to clamping force than has been accounted
for in the torque chart. True DRY threads seldom
exist as there are degrees of "oiliness" of different thread
lubricants. If oiled threads or anti-sieze compounds are
called for in a shop manual application, the manual will
also call out a specific torque value for the area discussed .
A manual might ask for a 10 percent reduction of torque
when engine oil is a lubricant to as high as a 40 percent
reduction of torque from the normal torque chart values
when an anti-sieze compound is used.
A new torque method is being used in certain shop manual
applications which is called a torque turn technique . Using
this method, the bolt is torqued to a very low setting which
is easy to obtain. Friction of the bolt head and/or dirt in
the threads are of little consequence as this method is
essentially a "snugging" process. After "snugged" to the
light torque value called for, the shop manual will call for
an additional 90 degree turn, or some specific number of
degrees. Using elaborate measuring procedures, GM Engineering
has determined that a service technician can,
arrive at a near ideal amount of bolt stretch for the given
bolt size and application and an ideal clamp load of the
workpieces.
STANDARDS FOR NUT AND BOLT GRADES
The basic standards for nut and bolt grades were established
by the Society of Automotive Engineers (S.A.E.).
General Motors has a corresponding rating system.
There are four basic grades of bolts used in assembly
today. They are as follows :
1 . S.A.E. GRADE 1, 2, 3, & 4 (GM-260M) -All have unmarked
bolt heads and are not heat treated .
2. S.A.E. GRADE 5 (GM-280M) -All have three (3) lines
on the bolt head dividing the head into three equal
parts . These bolts are carbon steel with rolled heads,
quenched and tempered in oil or water.
3. S.A.E. GRADE 6 & 7 (GM-290M) - All have four (4)
or five (5) lines on the bolt head which divide this head
into quarters or fifths.: These bolts are medium carbon
alloy steel with rolled heads, heat treated, quenched
in oil and drawn.
4. S.A.E. GRADE 8 (GM300M) -- All have six (6) marks
on the bolt head equally spaced around the top. These
bolts are made from carbon alloy steel, heat treated,
oil quenched and temper drawn at 800 degrees
Fahrenheit.
A-9
Nuts are available in three standard grades as follows :
1 . S.A.E. GRADE 2 - These are square nuts and are
used in some basic farm machinery, construction and
industrial machines. They are usually quite bulky and
do not contain the quality of steel used in automotive
nuts.
2. S.A.E GRADE 5 (GM-286M) - These nuts are made
of medium carbon steel and are not marked. They may
be plain steel or zinc coated and are used on bolts up
through S.A.E . Grade 5 or GM-280M bolts .
3. S.A.E. GRADE 8 (GM-301 M) -These nuts are made
of medium carbon steel that is heat treated and
quenched . They are marked with three (3) dots equally
spaced around the top surface of the nut . GM-301 M
nuts are made of special steel and are identified by a
copper flash or yellow chromate finish . Thick nuts such
as those used on spring U-bolts are also special nuts
that should not be substituted .
NOTE : S.A.E. GRADE 6 & 7 and GM-290M bolts are
production-only parts and not carried by GM
parts. If a replacement is needed, use Grade 8.
SERVICE TIPS
Some important points to observe are as follows :
" Always consult the appropriate shop manual for a given
bolt torque as the first torque preference. The following
torque charts are helpful for non-listed bolts.
USE A TORQUE WRENCH. Hand tightening is simply
a guessing game. An impact wrench (rattle gun) is more
of a guessing game than hand tightening .
" Never replace a bolt with one of a lesser grade than
the original .
" Do not exceed the nut or bolt torque listed on the charts
for the grade and size bolt being used.
Use lubricant on the bolt threads and/or head bearing
surface ONLY when called for in the service manual .
" Avoid using an impact wrench (rattle gun) to apply
torque values to any nut or bolt. (NOTE: Some factory
assembly line rattle guns can be used as they are generally
used in a specific application and torque accuracy
is checked each shift.) If an impact wrench is used on
torque prevailing nuts and bolts (nylon washer, strip or
patch), . it is recommended that the fasteners be replaced,
due to the abuse of the impact gun.
APPENDIX C
NUT AND BOLT IDENTIFICATION
(Cont'd)
Common metric fastener strength property classes are than the actual grade (i.e. grade 7 bolt will exhibit 5 em-
9.8 and 10.9 with the class identification embossed on bossed lines on the bolt head). Some metric nuts will be
the head of each bolt. Customary (inch) strength classes marked with single-digit strength identification numbers
range from grade 2 to 8 with line identification embossed on the nut face. The following figure illustrates the different
on each bolt head. Markings correspond to two lines less strength markings.
GRADE 2 GRADE 5 GRADE 7 GRADE 8
(GM 260-M) (GM 280-M) (GM 290-M) (GM 300-M)
Customary (inch) bolts - Identification marks correspond to bolt
strength- Increasing numbers represent increasing strength.
Metric Bolts - Identification class numbers correspond to bolt
strength - Increasing numbers represent increasing strength.
MANUFACTURERS NUT STRENGTH
IDENTIFICATION IDENTIFICATION
NUT AND BOLT IDENTIFICATION
POSIDRIV
SCREW HEAD
IDENTIFICATION MARKS (4)
APPENDIX C
NUT AND BOLT IDENTIFICATION
(Cont'd)
STANDARD CAPSCREW MARKINGS AND TORQUE
Current Usage Much Used Much Used Used at Times Used at Times
Minimum Tensile To 1/2-69,000 [476] To 3/4-120,000 [827] To 5/8-140,000 [965] 150,000 [1,034]
Strength PSI To 3/4-64,000 [421] To 1-115,000 [793] To 3/4-133,000 [917]
MPa To 1-55,000 13791
Quality of Material Indeterminate Minimum Medium Best Commercial
Commercial Commercial
SAE Grade 1 or 2 5 6 or 7 8
Number
Capscrew Head Markings
r
-
Manufacturer's '= 1
marks may vary
6 .-
are all SAE
Grade 5 (3 lines) 7
Y (GM280) (GM290) (GM300)
Capscrew Body Torque Torque Torque Torque
Size (Inches) - Ft.-Lb. [N"m] Ft.-Lb. [N"m] Ft.-Lb. [N"m] Ft.-Lb. [N"m]
(Thread)
1/4 -20 5 [7] 8 [ill 10 [141 12 [161
-28 6 [8] 10 [14] 14 [191
5/16-18 11 [15] 17 [231 19 [26] 24 [331
-24 13 [18] 19 [26] 27 [37]
3/8 -16 18 [24] 31 [42] 34 [46] 44 [60]
-24 20 [271 35 [47] 49 [66]
7/16-14 28 [38] 49 [66] 55 [75] 70 [95]
-20 30 [411 55 [751 78 [1061
1/2 -13 39 [53] 75 [102] 85 [115] 105 [142]
-20 41 [56] 85 [1151 120 [1631
9/16-12 51 [69] 110 [149] 120 [163] 155 [210]
-18 55 [75] 120(1631 170 [231]
5/8 - 11 83 [113] 150 [203] 167 [226] 210 [285]
-18 95 [129] 170 [231] 240 [325]
3/4 -10 105 [1421 270 [366] 280 [380] 375 [5081
-16 115 [156] 295 [400] 420 [569]
7/8 - 9 160 [2171 395 [5361 440 [5971 605 [8201
-14 175 [237] 435 [590] 675 [915]
1 - 8 235 [319] 590(8001 660 [8951 910 [12341
-14 250 [339] 660 [895] 990 [1342]
1 . Always use the torque values listed above when definite specifications are not available .
Note: Do not use standard values in place of those specified for the above engine groups. Special attention should be
observed in case of SAE Grade 6, 7 and 8 capscrews. Refer to applicable Shop Manual.
2. The above is based on use of clean and dry threads .
3. Reduce torque by 10% when engine oil is used as a lubricant.
4. Reduce torque to 20% if new plated capscrews are used.
CAUTION: CAPSCREWS THREADED INTO ALUMINUM MAY REQUIRE REDUCTIONS IN TORQUE OF 30% OR MORE,
UNLESS INSERTS ARE USED.
APPENDIX C
NUT AND BOLT IDENTIFICATION
(Cont'd)
METRIC TORQUE CHART- NEWTON-METERS **
Metric Bolt Grade
Bolt Diame - -
Metric Inch
' Torque Newton-meter
M5 .197 3 .2 4.4 5.5 7.2 8.8 . 12.1 13 .2
M6 .236 5.5 7.7 8.8 12.1 15.4 19.8 23.1
M7 .276 8.8 12.1 1 5.4 21 .9 26.4 30.3 38.5
M8 .315 13.2 17.6. 22 .0 29.7 37.4 48.4 55.0
M10 .394 25.3 35.2 40 .4 60.5 77.0 93.5 110.0
M12 .472 44.0 61 .6 77.0 104.5 132.0 165.0 198.0
M14 .551 7 1 .5 99.0 121 .0 132.0 209.0 264.0 308.0
M16 .630 110.0 154.0 187.0 297.0 319.0 418.0 484.0
M20 .787 220.0 291 .5 363.0 572.0 693.0 814.0 946.0
M24 .945 374.0 506.0 638.0 1012.0 1199 .0 1386.0 1628.0
M30 1 .181 748.0 1166.0 1440.0 2002.0 2387.0 2772.0 3234.0
1 . Always use the torque values listed above when definite specifications are not available .
2. The above is based on use of clean and dry threads .
3. Reduce torque by 10% when engine oil is used as a lubricant.
4. Reduce torque to 20% if new plated capscrews are used .
CAUTION: CAPSCREWS THREADED INTO ALUMINUM MAY REQUIRE REDUCTIONS IN TORQUE OF
30% OR MORE, UNLESS INSERTS ARE USED.
** NOTE: Use only when manufacturer's specifications are not available. These values are for stiff
metal-to-metal joints and are based on 90% of proof load. Do not use for gasketed joints or joints of
soft materials.
APPENDIX G
NUT AND BOLT IDENTIFICATION
(Cont'd)
Pipe Plugs and Fittings Torque
Hose Swivel Nut Torque
NON-LISTED TORQUE VALUES
Flared (Internal or External)
Tube Nut Torque
Note: Use these torque values when a specific
torque is not listed .
Flexible Sleeve Tube Fitting Torque
Hose Clamp Torque
Pipe
Thread
Size
In Bosses
or Aluminum
Ft./Lb. [N-m]
In Case
Iron or Steel
Ft./Lb. [N-m]
1/16 3.3-3.7 [4.5-5.0] 5-10 [7-14]
1/8 5-10 [7-14] 10-15 [14-20]
1/4 10-15 [14-20] 15-20 [20-27]
3/8 15-20 [20-27] 20-25 [27-34]
1/2 20-25 [27-34] 35-40 [47-54]
3/4 30-35 [41-47] 50-55 [68-75]
1 40-45 [54-61] 65-70 [88-95]
1-1/4 50-55 [68-75] 80-85 [108-115]
1-1/2 60-65 [81-88] 95-100 [129-136]
Tube Size Torque
Ft./Lb. [N-m]
3/16 7-7.5 [9-101
1/4 10-15 [14-20]
5/16 15-20 [20-27]
3/8 20-25 [27-34]
1/2 25-30 [34-41]
5/8 40-45 [54-611
3/4 45-50 [61-68]
7/8 50-60 [68-81]
1 60-70 [81--95]
Hose Size Torque
Ft./Lb. [N-m]
No. 4 4.5-5 [6-7]
No. 6 5-10 [7-14]
No. 8 15-20 [20-27]
No. 10 25-30 [34-411
No. 12 35-40 [47-54]
No. 16 50-60 [68-81]
No. 20 65-75 [88-102]
No. 25 90-100 [122-136]
No. 32 130-140 [176-190]
Tube Size Torque
Ft./Lb. [N-m]
1/4 inch 5-10 [7-14]
1/2 inch 10-15 [14-20]
7/8 inch 15-20 [20-27]
1-1/4 inch 20-25 [27-34]
Type ., Torque
In./Lb. [N-m]
T-Bolt 65-75 [7.3-8.5]
Worm Screw 35-45 [3.9-5.1]
APPENDIX C
NUT AND BOLT IDENTIFICATION
(Cont1d)
THREAD REPAIR INFORMATION
Occasionally, both internal and external threads may
become only partially stripped . In such cases, they
can often be repaired or cleaned up through the use
of a thread die or tap .
When threads in holes are damaged beyond repair,
there are generally three choices of corrective actions.
They are :
1 . The hole may be drilled and tapped to the next
suitable oversize and a larger diameter cap screw
or stud installed . Use a chart to determine the
proper tap size to use. A clearance or body drill
(a drill that is the size of the bolt's major diameter)
must be passed through the attaching part to allow
an oversize cap screw to be used.
2. The hole may be drilled and tapped to accept a
threaded plug. The plug is drilled and tapped to
the original screw size. A self-tapping plug that
is already threaded to the original size may be
used. For this repair, you must drill a hole to the
specified size, run a threaded plug into the hole
by using a cap screw and jam nut . When fully
seated, the jam nut is loosened and the cap screw
and jam nut are removed .
3. The hole may be drilled and tapped to accept a
patented coil wire insert called a Heli-Coil®. A
special tap is used that accomodates the odd size
of the Heli-Coil©. The Heli-Coil® is then inserted
using a special tool. This procedure brings the
hole back to its original diameter and thread specifications.
Heli-Coils© are available in standard
threads as well as metric threads .
THREADS DRILLED AND
STRIPPED TAPPED OVERSIZE
REPAIR STRIPPED THREADS
BY DRILLING AND TAPPING
TO NEXT OVERSIZE mSECA 11111111
CAP SCREW
INSERT THREADED PLUG
TO REPAIR STRIPPED
THREADS
LOCK OR
JAM NUT
THREADED PLUG
DRILLED AND
/TAPPED
STANDARD SCREW FITS
INTO HELI-COILS INSERT
HELI-COIL® FITS
TAPPED HOLE
REPAIR STRIPPED THREADS
USING A HELI-COIL°
A- 1 4
APPENDIX D
WEIGHT DISTRIBUTION AND
HELPFUL CONVERSIONS
Weight distribution of any special equipment item can be
determined if the centerline (CL) or the center of gravity
point is known in relation to the centerline of the axle.
Once this dimension is known, divide this dimension by
the wheelbase dimension.
The same rule applies if the centerline or center of gravity
point is outside the wheelbase (such as a liftgate, snowplow
or front-mounted winch) .
Determine the distance from the closest axle and divide
by the wheelbase. When the center of gravity point is
outside the wheelbase, it results in negative weight distribution
. In other words, the total amount of weight outside
the axle is added to the closest axle plus the amount of
weight that is taken off the opposite axle.
As an example, the body-payload weight distribution might
be 9/91 percent for a 14-foot body with a 167-inch WB
(wheelbase) - 102-inch CA (cab-to-axle) .
WEIGHT DISTRIBUTION FACTORS
50% 50%
100%
FRONT MOUNTED WINCH "41# 500 POUNDS
T
32"O 125" WB 0 630 LBS. -130 LBS.
00% - 100%
WEIGHT DISTRIBUTION
LOAD CENTER DIRECTLY IN MIDDLE
OF WHEELBASE.
50% FRONT AXLE
50% REAR AXLE
LOAD CENTER DIRECTLY OVER
CENTERLINE OF FRONT AXLE.
100% FRONT AXLE
0% REAR AXLE
LOAD CENTER DIRECTLY OVER
CENTERLINE OF REAR AXLE.
0% FRONT AXLE
100% REAR AXLE
LOAD CENTER OF WINCH 32"
BEYOND FRONTAXLE CENTERLINE .
32" DIVIDED BY 125"WB = 26°
126% OF WINCH WEIGHT ON
FRONT COMPONENTS. REAR
COMPONENTS LIGHTENED BY 26%.
LOAD CENTER OF DEAD-WEIGHT.
HITCH LOAD 50" BEHIND REAR
AXLE CENTERLINE . 50" DIVIDED
BY 125"WB = 40%.140% OF HITCH
LOAD ON REAR COMPONENTS .
FRONT COMPONENTS LIGHTENED
BY 40%.
A- 1 5
Substituting the correct figures in the formula shown
above would result in the following :
102 - 3 - 84 _ 15 = 8.98 or 9%
167 167
9% front, '91% rear
The 15" listed above means that the
centerline (CL) of the body is 15" forward
of the centerline (CL) of the rear axle.
Examples of weight distribution
appear on the chart below.
showing various factors
APPENDIX D
WEIGHT DISTRIBUTION AND
HELPFUL CONVERSIONS
(Cont'd)
HELPFUL CONVERSIONS AND CONSTANTS
1 Cubic Foot = 7.4805 Gallons
1 Cubic Foot = 1728 Cubic Inches
Pi = 3.14.16
To Determine
VOLUME OF A CYLINDER = Pi times radius
squared times length or height .
Most RV hot water tanks are 6 gallons, figure 50 to
55 pounds to include water in the plumbing.
Propane tanks are never filled more than 80% by law
to allow 20% expansion chamber for temperature
changes.
To Determine
VOLUME OF A BOX = Length times height times
depth.
To Determine
WEIGHT DISTRIBUTION INSIDE WHEELBASE _
Number of inches behind front wheel divided by
wheelbase. Example: 36" divided by 178" wheelbase
equals 20% weight added to rear wheels, 80% to,
front axle.
WEIGHT DISTRIBUTION OUTSIDE WHEELBASE
= Determine the distance from the closest axle and
divide by the wheelbase. Example: a hitch 144" behind
the axle divided by wheelbase of 178" equals
80% or 180% of hitch load on rear axle, the excess
over 100% being removed from the front axle.
Typical Weights
Water 8.328 pounds per gallon
Diesel fuel 7.0 pounds per gallon
Gasoline fuel 6.0 pounds per gallon
4 Propane C3H8 .23 pounds per gallon
MULTIPLY BY TO OBTAIN
Gallons 231 .0 Cubic Inches
Gallons 3.7854 Liters
Cubic Feet 1728.0 Cubic Inches
Cubic Feet 7.480 Gallons
APPENDIX D
WEIGHT DISTRIBUTION AND
HELPFUL CONVERSIONS
(Cont'd)
METRIC-ENGLISH CONVERSION TABLE
A-1 7
TO GET TO GET
EQUIVALENT EQUIVALENT
MULTIPLY BY NUMBER OF: MULTIPLY BY NUMBER OF:
LENGTH ACCELERATION
Inch 25.4 millimeters (mm) Foot/sect 0 .3048 meter/sect (m/s2)
Foot 0.3048 meters (m) Inch/sect 0.0254 meter/sect (m/s2)
Yard 0,9144 meters (m)
Mile 1 .609 kilometers (km) TORQUE
Inch pound 0.11298 newton-meters
AREA (N" m)
Inch2 645.2 millimeters 2 (mm2) Foot pound 1 .3558 newton-meters
6.45 centimeters2 (cm2)
Foot2 0.0929 meters2 (m2) POWER
Yard2 0.8361 meters2 (m2) Horsepower 0.746 kilowatts (kw)
VOLUME PRESSURE OR
Inch3 16387. mm3 STRESS
16.387 cm3 Inches of water 0.2491 kilopascals (kPa)
0.0164 liters (I) Pounds/sq. in. 6.895 kilopascals (kPa)
Quart 0.9464 liters (I)
Gallon 3.7854 liters (I) ENERGY OR WORK
Yard3 0.7646 meters3 (m3).
BTU 1 055. joules (J)
Foot pound 1 .3558 joules MASS (J) Kilowatt-hour 3 600 000. joules (J =one
Pound 0.4536 kilograms (kg) or 3.6 x 106 W's)
Ton 907.18 kilograms (kg)
Ton 0.907 tonne (t) LIGHT
Foot candle 1 .0764 lumens/meter2
FORCE (IM/M2)
Kilogram 9.807 newtons (N)
Ounce 0.2780 newtons (N) FUEL
Pound 4.448 newtons (N) PERFORMANCE
Miles/gal 0.4251 kilometers/liter
Degree TEMPERATURE degree (km/1)
Fahrenheit (F) -32 - 1 .8 = Celsius (C) Gal/mile 2.3527 liters/kilometer
°F (1/km)
T 3 98.6 212
-40 0 40 80 120 160 200 VELOCITY
Miles/hour 1 .6093 kilometers/hr .
-40 -20 0 20 40 60 80 100 (km/h)
'C 37 oC
APPENDIX D
WEIGHT DISTRIBUTION AND
HELPFUL CONVERSIONS
(Cont'd)
DECIMAL EQUIVALENTS
OF MILLIMETER, FRACTIONAL & NUMBER DRILL SIZES
A- 1 8
Millimeter
Dec.
Equiv.
Fractional
Number
Milllmeter
Dec .
Equiv.
Fractional
Numbar
Milli .
meter
Dec.
Equiv .
Fractional
Numbar
Milllmotor
Dec.
Equiv.
Fractional
Numbar
Millimeter
Dec.
Equiv.
Fractional
.1 .0039 1 .75 .0689 - .1570 22 6.8 .2677 10 .72 .4219 27/64
.15 .0059 - .0700 50 4 .0 .1575 6.9 .2716 11 .0 .4330
.2 . .0079 1 .8 .0709 - .1590 21 - .2720 1 11 .11 .4375 7/16
.25 .0098 1 .85 .0728 - .1610 20 - 7.0 .2756 11 .5 .4528
.3 .0118 - .0730 49 4.1 .1614 - .2770 1 11 .51 .4531 29/64
- .0135 80 1 .9 .0748 4 .2 .1654 7.1 .2795 11 .91 .4687 15/32
.35 .0138 - .0760 48 - .1660 19 - .2811 K 12.0 .4724
- .0145 79 1 .95 .0767 4.25 .1673 7.14 .2812 9/32 - 12 .30 .4843 31/64
.39 .0156 1/64 - 1 .98 .0781 5/64 - 4.3 .1693 7.2 .2835 12 .5 .4921
.4 .0157 - .0785 47 - .1695 18 7.25 .2854 12 .7 .5000 112
- .0160 78 . 2.0 .0787 4.37 .1719 11/64 - 7.3 .2874 13 .0 .5118
.45 .0177 2.05 .0807 - .1730 17 - .2900 L 13 .10 .5156 33/64
- .0180 77 - .0810 46 4.4 .1732 7.4 .2913 13 .49 .5312 17/32
.5 .0197 - .0820 45 - .1770 16 - .2950 M 13 .5 .5315
- .0200 76 2.1 .0827 4.5 .1771 7.5 .2953 13 .89 .5469 35/64
- .0210 75 2.15 .0846 - .1800 15 7.54 .2968 19/64 - 14 .0 .5512
.55 .0217 - .0860 44 4.6 .1811 7.6 .2992 14 .29 .5625 9/16
- .0225 74 2.2 .0866 - .1820 14 - .3020 N 14 .5 .5709
.6 .0236 2.25 .0885 4.7 .1850 13 7.7 .3031 14 .68 .5781 37/64
- .0240 73 - .0890 43 4.75 .1870 7.75 .3051 15 .0 .5906
- .0250 72 2.3 .0905 4.76 .1875 3/16 - 7.8 .3071 15 .08 .5937 19/32
.65 .0256 2.35 .0925 4.8 .1890 12 7.9 .3110 15 .48 .6094 39/64
- . .0260 71 - .0935 42 - .1910 11 7.94 .3125 5/16 - 15.5 .6102
- .0280 70 2.38 .0937 3/32 - 4.9 .1929 8.0 .3150 15 .88 .6250 5/8
.7 .0286 2.4 .0945 -, .1935 10 - .3160 0 16 .0 .6299
- .0292 69 - .0960 41 - .1960 9 8.1 .3189 16 .27 .6406 41/64
.75 .0295 2.45 .0964 5.0 .1968 6.2 .3226 16.5 .6496
- .0310 68 - .0980 40 - .1990 8 . - .3230 P 16.67 .6562 21/32
.79 .0312 1/32 - 2.5 .0984 5.1 .2008 8.25 .3248 17.0 .6693
.8 .0315 - .0995 39 - .2010 7 8.3 .3268 17.06 .6719 43/64
- .0320 67 - .1015 38 5.16 .2031 13/64 - 8 .33 .3281 21/64 - 17.46 .6875 11/16
- .0330 66 2.6 .1024 - .2040 6 8 .4 .3307 17.5 .6890
.85 .0335 - .1040 37 5.2 .2047 - .3320 O 17.86 .7031 45/64
- .0350 65 2.7 .1063 - .2055 5 8 .5 .3346 18.0 .7087
.9 .0354 - .1065 36 5.25 .2067 8 .6 .3386 18.26 .7187 23/32
- .0360 64 2.75 .1082 5.3 .2086 - .3390 R 18.5 .7283
- .0370 63 2.78 .1094 7/64 - - .2090 4 8 .7 .3425 18.65 .7344 47/64
.95 .0374 - .1100 35 5.4 .2126 8 .73 .3437 11132 19.0 .7480
- .0380 62 2 .8 .1102 - .2130 3 8 .75 .3445 19.05 .7500 3/4
- .0390 61 - .1110 34 5.5 .2165 8 .8 .3465 19.45 .7656 49/64
1 .0 .0394 - .1130 33 5.56 .2187 7/32 - - .3480 S 19.5 .7677
- .0400 60 2 .9 .1141 5.6 .2205 8 .9 .3504 19.84 .7812 25/32
- .0410 59 - .1160 32 - .2210 2 9 .0 .3543 20 .0 .7874
1 .05 .0413 3 .0 .1181 5.7 .2244 - .3580 T 20.24 .7969 51/64
- .0420 58 - .1200 31 5.75 .2263 9 .1 .3583 20.5 .8071
- .0430 57 3 .1 .1220 - .2280 1 9.13 .3594 23/64 - 20.64 .8125 13/16
1 .1 .0433 3 .18 .1250 1/9 - 5 .8 .2283 9.2 .3622 21 .0 .8268
1 .15 .0452 3 .2 .1260 5 .9 .2323 9 .25 .3641 21 .03 .8281 53/64
- .0465 56 3 .25 .1279 - .2340 A 9 .3 .3661 21 .43 .8437 27/32
1.19 .0469 3/64 - - .1285 30 5 .95 .2344 15/64 - - .3680 U 21 .5 .8465
1 .2 .0472 3 .3 .1299 6 .0 .2362 9.4 .3701 21 .83 .8594 55/64
1 .25 .0492 3 .4 .1338 - .2380 B 9.5 .3740 22 .0 .8661
1 .3 .0512 - .1360 29 6 .1 .2401 9.53 .3750 3/8 - 22 .23 .8750 7/8
- .0520 55 3 .5 .1378 - .2420 C - .3770 v 22 .5 .8858
1 .35 .0531 - .1405 28 6 .2 .2441 9.6 .3780 22 .62 .8906 57/64
- .0550 54 3 .57 .1406 9/64 - 6 .25 .2460 D 9.7 .3819 23 .0 .9055
1 .4 .0551 3 .6 .1417 6 .3 .2480 9.75 .3838 23 .02 .9062 29/32
1 .45 .0570 - .1440 27 6 .35 .2500 1/4 E 9.8 .3858 23.42 .9219 59/64
1 .5 .0591 3 .7 .1457 6 .4, .2520 - .3860 W 23.5 .9252
- .0595 53 - .1470 26 6 .5 .2559 9.9 .3898 23 .81 .9375 15/16
1 .55 .0610 3 .75 .1476 - .2570 F 9.92 .3906 25/64 - 24 .0 .9449
1 .59 .0625 1/16 - - .1495 25 6.6 .2598 10.0 .3937 24.21 .9531 61/64
1 .6 .0629 3.8 .1496 - ".2610 G - .3970 X 24 .5 .9646
- .0635 52 - .1520 24 6 .7 .2638 - .4040 Y 24 .61 .9687 31/32
1 .65 .0649 3 .9 .1535 6 .75 .2656 17/64 - 10.32 .4062 13/32 - 25 .0 .9843
1 .7 .0669 - ,1540 23 6.75 .2657 - .4130 Z 25.03 .9844 63/64
- .0670 51 3.97 .1562 5/32 - - .2660 H 10.5 .4134 25.4 1 .0000 1
1 mm = 0.03937 in. 1 yd . = 0.9144 m 1 sq. m = 1 .196 sq. yd .
1 cm = 0.3937 in. 1 sq . in. = 6.452 sq . cm 1 oz. = 31 .1035 grams
1 dm = 3.937 in. 1 sq . ft. = 929 sq. cm 1 lb . = 373.24 grams
1 m = 39.37 in. 1 sq . yd. = 0 .8361 sq. m 1 qt. = 0 .9463 liters (liquid)
1 in = 25.4 mm 1 sq . cm = 0.155 sq. in. 1 gal . = 3.7853 liters (liquid)
1 foot = 0 .3048 m 1 sq. dm = 15 .5 sq. in. 1 liter = 1 .0567 liquid qt.
WEIGHT DISTRIBUTION AND
HELPFUL CONVERSIONS
(Cont'd)
TORQUE CONVERSION TABLE
APPENDIX D
NEWTON-METERS
[N"m]
FOOT-POUNDS
..(-L)TA
1 0.7376
2 1 .5
3 2.2
4 3.0
5 3.7
6 4.4
7 5.2
8 5.9
9 6.6
10 7.4
15 11.1
20 14.8
25 18.4
30 22 .1
35 25.8
40 29.5
50 36.9
60 44.3
70 51.6
80 59.0
90 66.4
100 73.8
110 81.1
120 88.5
130 95.9
140 103 .3
150 110 .6
160 118.0
170 125 .4
180 132 .8
190 140.1
200 147.5
225 166 .0
250 184 .4
FOOT POUNDS
..(-L)TA
NEWTON-METERS
[N"m]
1 1 .356
2 2 .7
3 4.0
4 5.4
5 6.8
6 8.1
7 9.5
8 10.8
9 12 .2
10 13.6
15 20.3
20 27.1
25 33.9
30 40.7
35 47.5
40 54.2
45 61 .0
50 67.8
55 74.6
60 81 .4
65 88.1
70 94.9
75 101.7
80 108.5
90 122.0
100 135.6
110 149.1
120 162.7
130 176.3
140 189 .8
150 203.4
160 216.9
170 230.5
180 244.0
Air Bag Cylinder Inspection . . . . . . . . . . . . . . . 3-9
Air Bag Replacement . . . . . . . . . . . . . . . . . . . . 3-9
Air Cleaner-Polywrap . . . . . . . . . . . . . . . . 7-100
Air Cleaner Element Replacement . . . . . . . . 7-99
Air Conditioning Belt (Appendix A) . . . . . . . . . A-4
Air Conditioning System . . . . . . . . . . . . . . . . . 2-2
Air Conditioning System -
Optional (Appendix 2-1) . . . . . . . . . . . . . . . . . . 2-6
Air Distribution Section - A/C . . . . . . . . . . . . 2-5
Air Flow - Engine Compartment . . . . . . . . . . 7-4
Air Pump Drive Belt . . . . . . . . . . . . . . . . . . . . 7-99
A.I.R. Connector Diagram (Appendix 7-17) . 7-101
A.I.R. Connector Module (Appendix 7-17) . . 7-102
A.I.R. Filter Canister (Appendix 7-17) . . . . . . 7-105
Air Injection Reactor System -
Gasoline Engine . . . . . . . . . . . . . . . . . . . . . . . . 7-97
A.I.R. Pump Belt (Appendix A) . . . . . . . . . . . . . A-4
Alignment - Front Suspension . . . . . . . . . 3-1, 3-2
Automatic Transmission -350C and '
400-475 Series . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1
Automatic Transmission 4L8DE ...... . . . . . . . . . . . . . ... .. .8-7
Automatic Transmission Fluid . . . .. ...... . . . . . . . . . . . . . ....8-9
Automatic Transmission Manual Linkage 8-2, 8-5
Auxiliary Electrical Equipment
(Appendix 7-11) . . . . . . . . . . . . . . . . . . .
. . . . .
7-79
Auxiliary Fuel Tank Considerations . . . 7-29,7-30
Average Life of Gears . . . . . . . . . . . . . . . . . . . .
5-3
Axle Housing . . . . . . . . . . . . . . . . . . . . .
. . 5-3
B
Ball Joint Inspection . . . . . . . . . . . . . . . . . . . . 3-3
Battery . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 7-55
Battery Isolator . . . . . . . . . . . . . . . . . . . . . . . . 7-62
Battery Maintenance During Vehicle Storage
(Appendix B) . . . . . . . . . . . . . . . . . . . . . . . . . . . A-6
Battery Ratings . . . . . . . . . . .
. . . . . . . . . . . . .
7-55
Battery Removal and Replacement 7-59
Battery Size and Cranking (Appendix 7-10) . . 7-75
Belt Installation/Replacement (Appendix A) . . A-2
Belt Specifications (Appendix A) . . . . . . . A-3, A-4
Belt Wear (Appendix A) . . . . . . . . . . .. . . . .
. . .
A-1
Bent Axle Housing . . . . . . . . . . . . . . . . . .
.
. .
.
5-3
Bent Rim Check . . . . . . . . . . . . . . . . . . . . . . . 3-17
Bleeding Brakes . . . . . . . . . . . . . . . . . . . . . 6-7,6-8
Bolt Identification (Appendix C) . . . . . . . . . . . A-7
INDEX
-
(Appendix 6-3) . . . . . . . . . . . . . . . . . . . . . . . . . 6-14
Brake Master Cylinder . . . . . . . . . . . . . . . . . . . 6-5
Brake Pedal/Stoplight Adjustment . . . . . . . . . 6-6
Brake Rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
Brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
Built-in Hydrometer - Battery . . . . . . . . . . . 7-56
C
Caliper-Brake . . . . . . . . . . . ........ . . . . . . . . . . . .. ... . . . . . . . . . . . .. . 6-6
Camber .. .. . . . . . . . . . . . . . . .. .. ........ . . . . . . . . . .. ... .. . . . . . . . . . . . .....3-1
Canister Purge Control Valve . . . . . . . . . . . . . 7-96
Capscrew Markings (Appendix C) . . . . . . . . . A-11
Carburetor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31
Caster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Cast Iron Manifold . . . . . . . . . . . . . . . . . . . . . . 7-3
Center Bearing . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Certification Label .. . . . . . . . . . . . . . . . . . . . . 3-13
Changing Transmission Fluid . . . . . . . . . . . . . 8-4
Charging System .
. .
. .
. . . . . . . . . . .
. 7-62,7-64
Chassis . .. . . . . . . . .
. . . . . . . . . . . . .
. . . . . . . . 1-1
Check Valve Inspection . . . . . . . 7-99
Cold Advance Solenoid . . .
. . .
: . . . . . . . . . . 7-72
Cold Start Circuit -Diesel Engine . . . . . . . . 7-73
Compressor Assembly (Appendix 2-1) . . . . . . . 2-6
Condenser Assembly (Appendix 2-1) . . . . . . . . 2-7
Condenser Kit With Oil Cooler
(Appendix 2-1) . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
Condenser Kit Without Oil Cooler
(Appendix 2-1)
. . . . . . . . . . . . . . . .
. . . . . . . . . . 2-8
Condenser With Fans Wiring Diagram
(Appendix 2-1) . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
Conversions and Constants (Appendix D) . . A-16
Coolant Level . . . . . . . . . . . . . . . . . . . . . . . . . 7-17
Cooler Lines -
Automatic Transmission . . . . . . . . . . . . . . . . . 8-5
Cooling Fans . . . . . . . . . . . . . . . . . . . . . . . . . 7-14
Cooling Instructions To RV Manufacturers
(Appendix 7-3) . . . . . . . . . . . . . . . . . . . . . . . . . 7-21
Cooling System . . . . . . . . . . . . . . . . . . . 7-13,7-19
Cracked Wheel Stud Holes . . . . . . . . . . . . . . 3-16
Crankcase Ventilation - Diesel Engine . . . . 7-93
Cranking System . . . . . . . . . . . . . . . . . . . . . . 7-51
Cruise Control - Electronic (Appendix 7-16) 7-86
CS Series Generator . . . . . . . . . . . . . . . . . . . . 7-65
D
Deaeration Cooling System (Appendix 8-1) . . . 8-8
A B (Cont'd)
Accumulator - AC . . . . . . . . . . . . . . . . . . . . . 2-2 Boot Puller -Spark Plug . . . .. ... . . . . . . . . . . . .. ...... . . . . .7-71
Additives - Fuel . . . . . . . . . . . . . . . . . . .. . . . 7-22 Brake Bleeder-Vacuum (Appendix 6-2) .... . . .6-13
Additives - Radiator (Appendix 7-2) . . . . . . . 7-20 Brake Caliper Noise (Appendix 6-1) . . . . . . . . . . ...... . . .6-6
Add-On Electrical Equipment Brake Drum . . . . . . . . . . . . . . . . . . . . . . . . 6-3,6-5
(Appendix 7-11) . . . . . . . . . . . . . . . . . . . . . . . . 7-79 Brake Hose Inspection . . . . . . . . . . . . . . . . . . . 6-5
Aftermarket Fuel Systems (Appendix 7-8) . . . 7-50 Brake Lining . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5
Aftermarket Suspension Devices . . . . . . . . . 3-10 Brake Lining Life Expectancy
D (Cont'd)
.Decimal Equivalents (Appendix D) . . . . . . . . A-18
Detent Downshift Electrical Circuit
-400-475 Series Transmission . . . . . . . . . . . . 8-2
Determining Wheel/Tire Loads . . . . . . . . . . . 3-13
Diesel Engine . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2
Diesel Engine Fuel System . . . . . . . . . . . . . . 7-36
Diesel Glow Plug Electrical System . . . . . . . 7-71
Differential Fluid . . . . . . . . . . . . . . . . . . . . . . . 5-1
Differential Housing/Fill Hole . . . . . . . . . . . . . 5-1
Dipstick Replacement . . . . . . . . . . . . . . . . . . 7-10
Disc Brakes . . . . . . . . . . . . . . . . . . . . . . . . 6-296-6
Distributor - H.E.I . . . . . . . . . . . . . 7-66, 7-69,7 .70
Downshift (Detent) Cable -
350C Transmission . . . . . . . . . . . . . . . . . . . . . . 8-2
Drive Belt Tension (Appendix A) . . . . . . . .
. .
.A-1
Driveline Balance Procedure . . . . . . . 4-3, 4-4, 4-5
Driveline Noise . . . . . . . . . . . . . . .
.
.
. . .
.
.
. .
4-3
Driveline Vibrations - 1 and 2 Drive Shaft
Systems (Appendix 4-1) . . . . . . . . . . . . . . . . . . 4-6
Driveline Vibrations -3 Shaft Systems
(Appendix 4-2) . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
Drum Brakes . . . . . . . . . . . . . . . . . . . . . . . 6-3, 6-5
E
Early Fuel Evaporation
(ECM) System . . . . . . . . . . . . . . . . . . . . . . . . . 7-31
(EFE) System . . . . . . . . . . . . .
. . . .
7-93, 7-97, 7-98
Electrical Circuit Diagnosis -A/C . . . . . .
.
. . 2-5
Electrical Equipment - Add-On
(Appendix 7-11 . . . . . . . . . . . . . . . . . . . . . . . . 7-79
Electrical Load Test - Battery . . . . . . . . . . . 7-57
Electric Fuel Pump
(Appendix 7-7) . . . . . . . . . . . . . . . . . 7-40,742, 7-45
Electric Fuel Pump Relay Location
(Appendix 7-16) . . . . . . . . . . . . . . . . . . 7-102,7-104
Electronic Cruise Control (Appendix 7-16) . . . 7-86
Energy Conserving Oils . . . . . . . . . . . . . . . . .
.
7-8
Engine Cooling Fans . . . . . . . . . . . . . . . . . . . 7-14
Engine Cooling Instructions to
RV Manufacturers (Appendix 7-3) . . . . . . . . . 7-21
Engine Cooling System . . . . . . . . . . . . . . . . . 7-13
Engine Deaeration System . . . . . . . . . . .
.
. . 7-16
Engine Electrical System . . . . . . . . . . . . . . .
7-55
Engine Emission Controls . . . . . . . . . . . . .
7-92
Engine Fuel Systems . . . . . . . . . . . . . . . . .
. .
7-29
Engine Lubrication . . . . . . . . . . . . . . . . . . .
. . .
7-6
Engine Oil Consumption (Appendix 7-1) . .
. .
7-11
Engine Oil Hose Kit (Appendix 2-1) . . . . . .
. .
2-10
Engine Ratings and Specifications
- Diesel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2
Engine Ratings and Specifications -
Gasoline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2
Evaporative Control System . . . . . . . . . . . . . 7-29
Evaporative Emission Control System
(EECS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-94
INDEX (Cont'd)
E (Cont'd)
Exhaust Manifolds . . . . . . . . . . . . . . . 7-3, 7-4, 7-5
External Fluid Cooler (Appendix 8-1) . . . . . . . . 8-8
F
Fan Belt Application Chart (Appendix A) . . . . A-4
Fluids . . . . . . .
. . . . .
. .
. . . . . . . . .
.
. . . . .
1-4,8-7
Flushing Cooling System . . . . . . . . . . . . . . . . 7-19
Frame Angle Measurement . . . . . . . . . . . . . . . 3-3
Front Alignment . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Front Coil Spring Replacement . . . . . . . . . . . . 3-9
Front Suspension . . . . . . . . . . . .. . . . . . . . . . . . 3-8
Fuel Control Operation . . . . . . . . . . . . . . . . . 7-32
Fuel Filters . . . . . . . . . . . . . . 7-30, 7-35, 7-37, 7-38
Fuel Pump . . . .
.
.
. . . . . . . . . . . . . . . . . 7-29,7-35
Fuel Pump - Electric
(Appendix 7-6) . . . . . . . . . . . . . . . . . . . . . 7-40,7-44
Fuel Properties (Appendix 7-7) . . . . . . . . . . .
.
7-40
Fuel Return Line Plugged-(Appendix 7-6) . . . 7-39
Fuel Solenoid . . . . . . . . . . . . . . . . . . . . . . . . . 7-72
Fuel System Plumbing (Appendix 7-7) . . . . . . 7-40
Fuel Systems - Diesel Engines . . . . . . . . . . 7-36
Fuel Systems - Gasoline Engines . . . . . . . . 7-29
Fuel Tank . . . . .
. . . .
.
. . . . . . . . . . . . . . 7-29,7-36
Fuel Types -Diesel Engines . . . . . . . . . . . . 7-23
Fuel Types -
Gasoline Engines . . . . . . . . . . . . . 7-22, 7-24, 7-25
Fuel Vapor Canister - Auxiliary
. . .
.
.
. . . . . 7-96
Fuel Vapor Canister - Primary .
. . . . . . . . . .
7-95
Fuel Vapor Canister Purge Control Valve 7-96
Fuel VaporVent Control Valve . . . . . . . . . . . . 7-96
Gasohol . . . . . . . . . . . . . . . . . . . . . 7-22, 7-24, 7-25
Gasoline Blends (Appendix 7-5) . . . . . . . . . . . 7-25
Gasoline Engine . . . . . . . . . . . . . . . . . . . . . . . . 7-2
Gear Ratios (Appendix 8-4) . . . . . . . . . . . . . . . 8-12
Geared Road Speed Determination
(Appendix 8-3) . . . . . . . . . . . . . . . . . . . . . . . . . 8-11
Generator Belt (Appendix A) . . . . . . . . . . . . . . A-4
Generator Belt Usage - 6.2L Diesel
(Appendix 7-14) . . . . . . .
. .
.
. . . . . . . . . . . . . .
7-84
Generator Sizing and Selection 7-62
Glow Plug Lamp . . . . . . . . . . . . . . . . . . . . . . . 7-72
Glow Plug Relay . . . . . . . . . . . . . . . . . . . . . . . 7-72
Glow Plug System - 6.2L Engine . . . . . 7-63,7-72
Glow Plug Test . . . . . . . . . . . . . . . . . . .. . . . . . 7-74
G-Series Motor Home Chassis . . . . . . . . . . . . 1-1
H
Hard Steering -Engine Idle . . . . . . . . . . . . . . 3-6
Heating System . . . . . . . . . . . . . . . . . . . . . . . . 2-1
H.E.I . Distributor . . . . . . . . . . . . . . 7-66, 7-69, 7-70
H.E.I . Magnetic Pick-Up Assembly . . . . . . . . 7-68
Heli-Coil(& Thread Repair (Appendix C) . . . . A-14
H (Cont'd)
Helpful Conversions and Constants
(Appendix D) . . . . . . . . . . . . . . . . . . . . . . . . . . A-16
High Ambient Temperatures -
Starting Problem . . . . . . . .
. . . . .
. . . . . . . . . 7-61
"Hot Start" Problem Conditions
(Appendix 7-12) . . . . . . . . . . . .. . . . . . . . . . . . . 7-80
Hydraulic Brake System . . . . . . . . . . . . . . 6-1,6-7
Hydro-Boost Brake System . . . . . . . . . . . . 6-3,6-8
H5D Emission System (Appendix 7-16) . .
.
. 7-101
H5D Override Relay (Appendix 7-16) . . . . . . 7-103
Identification Numbers . . . . . . . . . . . . . .
. . . .
1-1
Idle Control . . . . . . . . . . . . . . . . . . . . . . . . . 7-34
Ignition System . . . . . . . . . . .
. . . . . . . . . .
. . .
7-66
Ignition Timing . . . . . . . . . . .
.
. ;
. . .
. . .
7-69
Increased Engine Life (Principles) . . . . 7-1
Inflation Pressure -Tires . . . . . . . . . . . 3-14,3-15
Injectors TBI . . . . . . . . . . . . . . . . . . . . . . . . . . 7-33
Isolator - Battery . . . . . . . . . . . . . . . . . . . . . 7-62
Isolator Diagnosis . . . . . . . . . . . . . . . . . . . . . 7-65
J
Journal Cross . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Jump Starting Aid . . . . . . . . . . . . . . . . . . . . . . 7-58
Jump Starting With Auxiliary Battery . . . . . . 7-57
L
Lateral Runout Measurement . . . . . . . . . . . . 3-17
Load Height Curves (Appendix 3-2) . . . . 3-21, 3-22
Lower Ball Joint Inspection . . . . . . . . . . . . . . . 3-3
Lubricant Capacities . . . . . . . . . . . . . . . . . . . . 1-5
Lubricants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . 1-4, 7-6
Lubrication Points . . . . . . . . . . . . . . . . . . . 1-6,1-7
M
Magnetic Switch Mounting (Appendix 7-12) . 7-80
Manual Linkage - Transmission . . . . . . . 8-2,8-5
Master Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . 6-5
Methanol/Gasoline Blends (Appendix 7-5) . . 7-25
Metric-English Conversion Table
(Appendix D) . . . . . . . . . . . . . . . . . . . . . . . . . . A-17
Metric Torque Chart (Appendix C) . . . . . . . . . A-12
Modifications for Diesel Starting . . . . . . . . . . 7-73
Motor Home Towing . . . . . . . . . . . . . . . . . . . . . 1-3
Multi-Battery Electronic Jump Starting Aid . 7-58
N
Needle Bearings . . . . . . . . . . . . . . . . . . . . . . . . 4-24
Nodular Iron Manifold . . . . . . . . . .
. . . . .
. . . . 7-3
Nut and Bolt Failures/Fatigue (Appendix C) . . A-8
Nut and Bolt Identification (Appendix C) . . . . A-7
INDEX (Cont1d)
N (Cont'd)
Nut and Bolt Standards/Grades
(Appendix C) . . . . . . . . . . . . . . . . . . . . . . A-9, A-10
0
Oil Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9
Oil Consumption (Appendix 7-1) . . . . . . . . . . 7-11
Oil Fill Capacity - 454 Engine . . . . . . . . . . . . 7-9
Oil Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9
Oil Hose Kit (Appendix 2-1) . . . . . . . . . . . . . . . 2-10
Oil Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9
Oil Pressure Switch Relay
(Appendix 7-7) . . . . . . . . . . . . . . . . . . . . . 7-42,7-44
Oil Quality . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 7-7
Oil Temperature . . . . . . . . . . . . . . . . . . . . . . . . 7-8
Oil Viscosity . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
Optional A/C System (Appendix 2-1) . . . . . . . . 2-6
Overheating Tires . . . . . .. . . . . . . . . . . . . . . . . 3-18
Overinflation - Tire Wear . . . . . . . . . . . . . . . 3-18
Overloaded Gears . . . . . . . . . . . . . . . . . . . . . . . 5-3
Overloading Tires . . . . . . . . . . . . . . . . . . . . . . 3-18
Parking Brake . . . . . . . . .. ........ .. . . . . . . . . . .. ... . . . . . . . . . . . 6-4, 6-8
Parking Brake Cable Adjustment . . . . . . . . . . .. ...... . . . . .6-9
Parking Brake Drum Balance .. ... . . . . . . . . . .. .. ...... . . . . .6-9
PCV Filter Replacement . . . . . . . . . . . . . . . . . 7-97
PCV System -Gasoline Engine . . . . . . 7-92,7-97
Pedal Travel - Brakes . . . . . . . . . . . . . . . . . . . 6-5
Plugged Fuel Return Line (Appendix 7-6) . . . . 7-39
Polywrap Air Cleaner . . . . . . . . . . . . . . . . . . 7-100
Poor Ground - Starting Problem . . . . . . . . . 7-61
Power Brake Unit . . . . . . . . . . . . . . . . . . . . 6-3,6-8
Power Steering Belt Application Chart
(Appendix A) . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4
Power Steering Component Replacement . . . 3-7
Power Steering Leak Check . . . . . . . . . . . . . . . 3-6
Power Steering Pump Belt Tension
Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
Power Steering System . . . . . . .
. . . .
. . . . . .
. 3-5
Power Steering Quick Fixes . . . .
. . .
.
. 3-7
Preparation for Storage (Appendix B) . . . . . . . A-5
Pressure Cap - Radiator . . . . . . . . . . . . . . . 7-11
Pressure Regulator . . . . . . . . . . . . . . . . . . . . . 7-33
Pressurized Fuel System Components
(Appendix 7-7) . . . . . . . . . . . . . . . . . . . . . . . . . 7-44
Pressurized Fuel System Diagnosis
(Appendix 7-7) . . . . . . . . . . . . . . . . . . . . . 7-48,7-49
Primary Fuel Filter Water Drain . . . . . . . . . . . 7-37
Principles of Increased Engine Life . . . . . . . . . 7-1
Propeller Shaft . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Propeller Shaft Drum Brake Adjustment . . . . . 6-9
P-Series Motor Home Chassis . . . . . . . . . . . . . 1-1
R
Radial/Lateral Runout Measurement . . . . . . 3-17
Radiator Additives (Appendix 7-2) . . . . . . . . . 7-20
Radiator Heater and Engine Deaeration
System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16
Radiator Hose Application Chart
(Appendix A) . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4
Radiator Pressure Cap . . . . . . . . . . . . . . . . . . 7-11
Rear Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
Rear Axle Lubrication Fill Hole . . . . . . . . . . . . 5-1
Rear Spring Installation . . . . . . . . . . . . . . . . . 3-12
Rear Suspension . . . . . . . . . . . . . . . . . . . . . . 3-12
Receiver-Dehydrator- A/C . . . . . . . . . . . . . . . 2-2
Recommended Fluids and Lubricants . . . . . . 1-4
Refrigeration Section - A/C . . . . . . . . . . . . . . 2-4
Ride Height Measurement . . . . . . . . . . . . . . . . 3-2
Rim Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17
Rotor - Brake . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
S
Secondary Wiring - H.E.I. Distributor . . . . . 7-67
Secondary Fuel Filter . . . . . . . . . . . . . . . 7-38,7-52
Service Parts Identification Label . . . . . . . . . . 1-3
Shock Absorber Diagnosis . . . . . . . . . . 3-10,3-12
Side Fill Gear Case Capacity . . . . . . . . . . . . . . 1-5
Slip Spline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Slow Cranking Diagnosis
(Appendix 7-10) . .
. . . . . . . . . . . . . . . . . .
7-77,7-78
Solenoid Diagnosis (Appendix 7-10) 7-77,7-78
Solenoid Electrical Operation . . . . . . . . . . . . 7-61
Solid State Isolator . . . . . . . . . . . . . . . . . . . . . 7-65
Spacer Block . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
Spark Plug Boot Puller . . . . . . . . .
. . . . . . . . . 7-71
Spark Plugs . . . . . . . . . . . . .
. . . . 7-67, 7-68, 7-69
Spark Plug Wires . . . . . . . . . . . . . . . . . . . . . . 7-70
Special Suspension Equipment
(Shock Absorber) . . . . . . . . . . . . . . . . . . . . . . 3-10
Specifications - Drive Belts (Appendix A) . . A-1
Stainless Steel Manifold . . . . . . . . . . . . . . . . . 7-3
Starter Motor Relay Connections
(Appendix 7-13) . . . . . . . . . . . . . . . . . . . . . . . . 7-83
Starter Motor Engagement (Appendix 7-13) . 7-83
Starting Motor . . . . . . . . . . . . . . . . . . . . . . . . 7-59
Starting Problems . . . . . . . . . . . . . . . . . . . . . 7-61
Steering Damper Check . . . . . . . . . . . . . . . . . .. 3-4
Steering Linkage . . . .
. . .
.
. . . . . . .
. .
. . . . . .
3-4
Steering Linkage Lubrication . . 3-4
Steering Linkage Support Assemblies . . . . . . 3-4
Steering Relay Parts Identification
(Appendix 3-2) . . . . . . . . . . . . . . . . . . . . . . . . . 3-20
Steering System . . . . . . . . . . . . . . . . . . . . . . . . 3-4
Storage of Motor Home (Appendix B) . . . . . . . A-5
Stripped Thread Repair (Appendix C) . . . . . . . A14
Stud Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16
Suspension Devices - Aftermarket . . . . . . . 3-10
INDEX (Cont'd)
S (Cont'd)
Suspension System . . .
. . . . . . .
.
. .
. . . . . . . . 3-8
Synthetic Engine Oil . . . . . . . . . . . . 7-8
T
TBI Fuel Injection . . . . . . . . . . . . . . . . . . . . . . 7-31
Temperature Monitors (Appendix 8-2) . . . . . . 8-10
Thermostat . . . . . . . . . . . . . . . . . . 7-13, 7-14, 7-19
Thermostatic Air Cleaner (Thermac) . . . 7-93,7-99
Thread Repair Information (Appendix C) . . . A-14
Tie Rod Parts Identification (Appendix 3-1) . . 3-20
Timing - Ignition . . . . . . . . . . . . . . . . . . . . . . 7-69
Tire Balancing . . . . . . . . . . . . . . . . . . . . . . . . . 3-14
Tire Inflation . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18
Tire Inspection and Rotation . . . . . . . . . . . . . 3-13
Tire Overheating . . . . . . . . . . . . . . . . . . . . . . . 3-18
Tire Overloading . . . . . . . . . . . . . . . . . . . . . . . 3-18
Tire Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10
Tire Replacement . . . . . . . . . . . . . . . . . . . . . . 3-14
Tires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13
Tire Size and Load Limits (G-Series) . . . . . . . 3-14
Tire Size and Load Limits (P-Series) . . . . . . . . 3-15
Tire To Rim Matching . . . . . . . . . . . . . . . . . . . 3-17
Tire Wear and Rotation . . . . . . . . . . . . 3-18,3-19
Toe-in . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Torque Converter Clutch . . . . . . . . . . . . . . . . . 8-2
Torque Conversion Table (Appendix D) . . . . . A-19
Torque Values (Appendix C) . . . . A-11, A-12, A-13
Torque Wrerich Applications (Appendix C) . . . A-8
Torsional Isolator (Appendix 7-15) . . . . . . . . . 7-85
Towing . . . . . . . . . . . . : . . . . . . . . . . . . . . . . . . 1-3
Throttle Position Sensor (TPS) . . . . . . . . . . . . 7-34
Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1
Transmission Controls . . . . . . . . . . . . . . . . . . . 8-2
Transmission Failure (Appendix 8-1) .' . . . . . . . 8-7
Transmission Fluid . . . . . . . . . . . . . . . 8-3, 8-4, 8-7
Transmission Mounts . . . . . . . . . . . . . . . . . . . 8-5
Transmission Shifting . . . . . . . . . . . . . . . . . . . 8-5
Troubleshooting Aftermarket Fuel Systems
(Appendix 7-8) . . . . . . . . . . . . . . . . . . . . . . . . . 7-50
Troubleshooting Heater and A/C Systems . . . 2-1
V
U-Bolt Torque Specifications - Rear . . . . . . 3-12
Underinflation -Tire Wear . . . . . . . . . . . . . . 3-18
Underloaded Gears . . . . . . . . . . . . . . . . . . . . . 5-3
Universal Joint Failures . . . . . . . . . . . . . . . . . . 4-2
Universal Joints . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Unleaded Gasoline . . . . . . . . . . . . . . . . . . . . . 7-22
V
Vacuum Brake Bleeder (Appendix 6-2) . . . . . 6-13
Vacuum Modulator System . . . . . . . . . . . . . . . 8-2
Vacuum System Diagnosis - A/C . . . . . . . . . 2-5
V (Cont'd)
Vapor Lock Cause and Cure
(Appendix 7-7) . . . . . . . . . . . . . . . . . . . . . . . . . 7-40
Vapor Vent Control Valve . . . . . . . . . . . . . . . . 7-96
Vehicle Emission Control Information Label 7-92
Vehicle Identification Number Codes . . . . . . . 1-2
Vehicle Identification Number (VIN) . . . . . . . . 1-2
Vehicle Load Conditions -
Shock Absorber . . . . . . . . . . . . . . . . . . . . . . . 3-10
Vehicle Ride and Handling Check . . . . . . . . . 3-11
Vehicle Ride Height . . . . . . . . . . . . . . . . . . . . . 3-9
Vibration Checks . . . . . . . . . . . . . . . . . . . . . . . 4-3
Viscosity - Oil . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
Water in Fuel . . . . . . . . . . . . . . . . . . . . . . . . . 7-37
Weight Distribution (Appendix D) . . . . . . . . . A-15
Wheel and Stud Bolt Failures . . . . . . . . . . . . 3-16
Wheel and Tire Balancing . . . . . . . . . . . . . . . 3-14
Wheel Bearing Adjustment . . . . . 3-8, 3-9, 5-1, 5-2
Wheel Bearing Lubrication . . . . . . . . . . . . 3-8,5-2
Wheel Code and Limits -G-Series . . . . . . . 3-14
Wheel Code and Limits - P-Series . . . . . . . . 3-15
Wheel Nut Tightening Sequence . . . . . . . . . . 3-16
Wheels and Tires . . . . . . . . . . . . . . . . . . . . . . 3-13
Wheel Stud Bolt Replacement . . . . . . . . . . . . 3-16
Worn/Cracked Wheel Stud Holes . . . . . . . . . 3-16
INDEX (Cont'd)
<:~7
CHEVROLET WARRANTY COVERAGE RECAP
Gee 1985 THRU 1994
LIGHT DUTY TRUCKS
See separate warranty folder.
Refer to policies & procedures manual to see if owner qualifies for 60150 coverage .
With $100 deductible after 12112.
First 12 months 1 unlimited mileage - no deductible.
No deductible on portion factory installed =Condenser -Compressor.
1990-91 has 601100 warranty.
1992 $100 deductible after 36136.
DEL.ON / AFTER 3/16/87 DEL.BEFORE 3/16/87
COVERAGE 1988 1988 1987 1987 1987 1987
1989 1ST OWNER 1 ST OWNER I ST OWNER
1992
1994
1990
1991
&
2ND OWNER
2ND OWNER
WITHOUT
& 2ND OWNER & 2ND OWNER 1985
W/TRANS. TRANSFER
2ND OWNER
W/TRANS.
WITHOUT
TRANSFER
2ND OWNER
W/TRANS.
WITHOUT
TRANSFER
1986
MTHS/MILE MTHS/MILE MTHS/MILE MTHS/MILES MTHS/MILE MTHS/MILES MTHS/MILES MTHS/MILES MTHS/MILE
BASE WARRANTY (EXCEPT TIRES)©' 36/36 36/50103 12/12 12/12 12/12 12/12 12/12 12/12 12/12
AIR CONDITIONING 36/36 15 36/50 14 12/UNLTD 12/UNLTD 12/UNLTD 12/UNLTD 12/UNLTD 12/UNLTD 12/UNLTD
POWERTRAIN COMP.
W/$100 DEDUCT AFTER 12/12 36/36 15 36/50 72/60 24/24 72/60 24/24 72/60 24/24 24/24
EMISSION PERFORMANCE WARRANTY 7 60/50 60/50 60/50 60/50 60/50 60/50 60/50 60/50 60/50
DIESEL ENGINES W1100
DEDUCTIBLE AFTER 12112 6011008 3W508 72160 36150 ' 72160 36150 72160 36/50 36150
CQ7 CHEVROLET
CHEVROLET MOTOR DIVISION G
General. Motors Corporation
Technical service Department
subject : AUTOMATIC APPLY PARKING BRAKE
Model and Year : 1990 P3 MOTOR HOME (16,000# GVW ONLY)
TO : ALL CHEVROLET DEALERS
Operational Features
Parking Brake Adjustment
1 . Adjusting the brake-to-drum clearance.
Back off the adjuster two to four notches .
Dealer
Service
Bulletin
Adjust screw through the drum opening until the brake just locks up .
_ 90-391-5
Number :
5
Section :
December 1990
Date :
065020
Corporate Bulletin No . :
THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO.
90-367-5, DATED OCTOBER 1990 . THE MODEL DESIGNATION HAS BEEN CORRECTED.
ALL COPIES OF 90-367-5 SHOULD BE DISCARDED.
The parking brake system on the 1990 16,000 pound GVW P3 motorhome chassis
incorporates a unique automatic apply feature with an internal expanding parking brake.
The system is different than the 1989 and 1991 systems of the same model. The parking
brake is spring applied and hydraulically released . Hydraulic pressure is supplied by the
power steering pump. Full brake disengagement requires that 95-115 PSI pressure exists
at the brake actuator .
The parking brake can be applied by using a hand button or automatically when the shift
lever is in the park position . The system features an HR-1 relay valve serving as a flow
control point. The HR-1 reduces and directs flow to and from a spring actuator operating
the parking brake (see Figure 1) .
1 . In the event the vehicle stalls, the wheels can be spun freely for at least ten minutes
until pressure is drained from the brake actuator and the spring brake reapplies .
2 . A parking brake light in the vehicle warns the operator when the brake is applied. This
brake light will come on when the pressure at the actuator is less than 60 PSI .
Chevrolet bulletins are intended for use by professional technicians, NOT a "dolt-yourselfer ." They are written to inform
these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do ajob
properly and safely . If a condition is described, DO NOT assume that the bulletin applies to yourvehicle, or that your vehicle
will havethatcondition. See your Chevrolet dealerfor information on whether your vehicle maybenefit from that information.
GSD 148D Rev. 12/89
2. Adjusting the cable free play (see Figure 2) .
3. Adjust the transmission linkage (see Figure 3) .
Bleed Procedure 1
1 . Fill the power steering pump fluid reservoir to the proper level and let the fluid settle
for at least a few minutes .
2 . Start the engine and let it run for a few seconds; then turn off the engine .
3 . Add fluid, if necessary.
4. Repeat the above procedure until the fluid level remains constant after running the
engine.
5. Block the rear wheels or raise them off the ground.
6. Raise the front of the vehicle,so the wheels are off the ground.
7 . Start the engine, put the transmission in neutral, and place the park apply button in
the release position. Slowly turn the steering wheel right and left, lightly contacting the .,
wheel stops.
90-391-5
Drum should spin free with only light drag .
Loosen the jam nut towards the brake actuator.
Turn the 3-inch-long hex nut along the stud until no free play exists .
Move the jam nut until it is against the 3-inch-long hex nut.
The actuator should stroke between .75 and 1 .00 inch when properly adjusted.
Apply the parking brake.
Loosen the screw (226) .
To put the transmission in neutral, move the shift lever (A) to the forward position,
then back to the second detent .
Hold the rod (240) tightly in the swivel (244). Tighten the nut (226) to 23 N.m (17
lbs. ft.) .
Put the column selector lever in the "P" (park) position.
Put the column selector lever in the neutral position. Put the lever into the neutral
gate, do not use the indicator to find the neutral position.
Check the adjustment. The column selector lever must go into all positions. The
engine must start in the "P" (park) or "N" (neutral) positions only.
-3-
8. . Check the fluid level and add fluid, if necessary.
9. Lower the vehicle and turn the steering wheel slowly from lock to lock.
10 . Stop the engine. Check the fluid level and refill as required .
11 . If the fluid is extremely foamy, allow the vehicle to stand a few minutes and repeat the
above procedure.
12 . If air still remains in the system, proceed on to bleed procedure 2.
Bleed Procedure 2
1 : Secure the vehicle.
2. With the engine running, move the shift lever from the park to the neutral position.
3 . Back off the bleed nut on the actuator and allow the system to self-bleed.
4 . Tighten the actuator bleed part and cycle the system.
5 . If air still remains in the system, proceed on to bleed procedure 3.
Bleed Procedure 3
1 . Secure the vehicle.
2: Crack open the exhaust fitting of the manual control valve .
3 . Engage the parking brake using the manual control valve.
4 . Allow a small amount of fluid to bleed out of the fitting, then quickly tighten the fitting .
5 . Repeat bleed procedures 1-3, as required .
Replacing the HR-1 Relay Valve
1 . Removal
Block the wheels and shut off the engine.
Disengage the parking brake by running the actuator arm nut down against toe
bracket retaining the stud in a released position.
Mark all lines and fittings .
" Remove all lines from the HR-1 .
2 . Installation
" Qonnect all lines to the HR-1 . Be careful to use the marks made upon removal.
" Check fluid in reservoir.
90-391-5
3. Adjusting the transmission linkage .
" Refer to the service manual. 1990 RN,G,P models 7A1-55 shift linkage adjustment.
HR-1 Relay Valve Bleeding Procedure 1
" Secure the vehicle.
" With the engine running, move the shift lever from the park to the neutral,
position .
Perform system tests outlined in this service bulletin .
Move the dam nut until it is against the 3-inch-long hex nut.
Open the port on the actuator and allow the system to self-bleed.
Tighten the actuator bleed port and cycle the system.
" If a whine noise can be heard, air still remains in the system; proceed on to
Bleeding Procedure 2.
HR-1 Relay Valve Bleeding Procedure 2
90-391-5
Secure the vehicle.
" Crack open the exhaust fitting of the manual control valve.
" Engage the parking brake using the manual control valve.
" Allow a small amount of fluid to bleed out of the fitting; then quickly tighten the
fitting.
" If air still remains in the system, bleed the power steering system as described
in the service manual.
DIAGNOSTIC INFORMATION :
The following Diagnostics Charts 1 and 2 can be used to to determine if the Automatic
Apply Parking Brake System is functioning normally and to identify what repairs may be
required .
RESERVOIR MANUAL APPLY SHIFT ACTUATED
CONTROL VALVE CONTROL VALVE
Figure 1-Parking brake system
Figure 2
NOTE: Improper adjustment of the park brake shoes or actuator can cause air noise in the power steering systems .
Step 1 - Reference page 6-9 propeller shaft drum-type brake adjustment.
Step 2 - Block wheels - Engine running - Park Position
A - Check actuator cable length inside support bracket to #2 hex -nut.
B - Block wheels - Engine running - Neutral Position
CAUTION: Have someone in driver seat with service brake applied - recheck above cable length. Movement of
cable should be 1 .20 inches to 1 .44 inches. Movement over 1 .44 inches will allow power steering reservoir to empty
and draw air causing power steering noise after each cycle of the actuator (See Figure 2).
A. SHIFT LEVER
B . STEERING COLUMN
226 . SCREW
227. RETAINING PIN
228. NUT
229. SPRING
231 . INSULATOR
232. RETAINING PIN
238. EQUALIZER LEVER
240. ROD
241 . BEARING
242. INSULATOR
243. WASHER
244. SWIVEL
90-391-5
Figure 3 -Shift Linkage
1 . Bleed the system.
2 . Adjust the cable freeplay .
3. Adjust the brake to drum
clearance .
4. Adjust the transmission
linkage .
Check all lines and
fittings for leaks and
proper routing . Replace if
necessary .
90-391-5
Inspect the brake actuator.
Replace if necessary .
If the system is still not
functioning properly the
HR-1 relay valve is
malfunctioning . Replace
the HR-1 relay valve.
-8-
DIAGNOSTIC CHART 1
Secure the vehicle by blocking
its front wheels.
With the parking brake released
turn off the engine .
Propshaft will not spin Propshaft spins freely
freely at all . for at least 10 minutes.
System unchanged
System unchanged
System unchanged
Jack up the rear and spin the
propshaft .
OK
OK
OK
System functioning properly.
Resume vehicle operation.
Propshaft spins freely
with light drag.
1 . Bleed the system.
2 . Adjust the cable freeplay.
3 . Adjust the brake to drum
clearance .
4. Adjust the transmission
linkage .
90-391-5
Secure the vehicle by blocking
its front wheels.
Set the parking brake using the
manual apply button.
System unchanged
Check all hydraulic lines
and fittings . Repair any
leaks. Check lines for
proper routing .
System unchanged
Inspect the brake actuator.
Replace if necessary.
System unchanged
If the system is still not
functioning properly the
HR-1 relay valve is
malfunctioning . Replace
the HR-1 relay valve.
-9-
DIAGNOSTIC CHART 2
OK
OK
OK
Propshaft will not spin .
System functioning properly.
Resume vehicle operation .
'CHEVROLET
CHEVROLET MOTOR DIVISION Ge
General Motors Corporation
Technical Service Department
subject: HYDRAULIC FLUID/LEAKING
HYDRAULIC PARK BRAKE VALVE SEAL
Model and Year : 1990 P316000 LB. MOTOR HOME (RPO C7P)
Dealer
Service
Bulletin
Number :
Date :
90-435-5
5
Section:
OCT. 1991
165007
Corporate Bulletin No .:
A5
ASE No.:
Some owners of 1990 P3 16000# motor homes may experience a condition where the hydraulic park apply
control valve leaks hydraulic fluid. This does not affect the parking brakes while they are applied . The cause
may be an undersized O-ring which allows the fluid to pass out of the valve and/or a cap nut with insufficient
thread which results in insufficient torque . For vehicles with the above condition, the O-ring and cap nut
should be replaced and threaded surfaces torqued to the specifications listed below. Additional parts are
provided in the repair kit and should be used if necessary.
Note: Excessive torquing of the cap nut (Figure 1, View A, #4) may result in the crushing of the . bottom
portion of the control valve.
SERVICE PROCEDURE: (Figure 1)
1 . Place transmission in park position, set manual appl park brake by putting manual control knob in the
on position. Leave the ignition in the off position. Put locks on wheels.
2. Detach the left front wheel well panel. Retain all fasteners and panel for the reinstallation process.
Locate the control valve (Figure 1). Prepare the removal area by having a towel or rag available to catch
any oil leakage from the pipe/valve.during removal.
3. Detach the supply pipe assembly at the elbow fitting (#5) . Gently move pipe out of area to facilitate
removal of the cap nut (#4) and elbow (Figure 1, View A, #5). The seal (#3) may not drop out due to oil
viscosity; it may be necessary to use a thin pick to dislodge the seal (#3) from inside valve. Disconnect
elbow from cap nut.
4. Prior to assembly, lubricate bores, O-ring, and threads with lubriplate (P/N 1050109) or equivalent .
Install replacement O-ring (#3) over replacement cap nut (#4); place spring (#2) on inner pocket of cap
nut (#4) and rest seal (#1) on top of the spring (#2) . Balancing this assembly, gently raise into the valve
body. Upon making contact with the valve, hand tighten assembly. Then torque cap nut (4) to 6-16 N.m .
(5-12 lbs. ft.) in proper alignment with supply pipe.
5 . Apply thread sealant to threads going into cap nut (#4) and threaded surface of elbow (#5). Thread
elbow (#5) into cap nut (#4) and torque elbow to 12-14 N.m. (9-10 lbs. ft.) . The final alignment of the
elbow (#5) should be in the same direction as the plugged fitting located above the elbow (#5).
CAUTION: Do not apply sealant over the elbow opening.
6 . Reattach the supply pipe by gently bending it back into position ; insert pipe into the elbow (#5) and
torque the nut to 12-14 N.m. (9-10 lbs. ft.).
NOTE : To maintain proper fluid level throughout the bleed procedure,* check and fill the power steering
reservoir as necessary with power steering fluid (P/N 1050017) .
Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer," They are written to inform these technicians of conditions that
may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment,
tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your
vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information.
GSD 1480 Rev. 12189
7. Leaving vehicle transmission in park position, bleed system by starting vehicle and allowing 30
seconds to elapse ; then loosen the supply pipe nut just enough to allow air to escape the system .
Prepare the area by having a towel or rag available to catch any oil leakage. When leakage occurs,
retorque supply pipe nut to 12-14 N.m. (9-10 lbs. ft.). Put the manual control knob in "OFF" position,
cak delivery ("0') fitting on manual control valve to bleed. Release and set the manual apply park
brake s x times to help the bleeding process. Retorque delivery fitting of manual control valve. Turn
off engine ; inspect valve and fitting for leakage; tighten as required .
8. Retrieve and reinstall retained fasteners and wheelhouse panel that were detached in Step 2.
SERVICE PARTS INFORMATION:
Part
Number Description Quantity
15680238 Seal Repair Kit 1
1050109 Lubriplate As Required
1050017 Power Steering Fluid As Required
NPN Teflon Tape As Required
Parts are currently available from GMSPO.
WARRANTY INFORMATION:
For vehicles repaired under warranty use:
Labor Operation: T7296
Labor Time: 0.6 hr.
NOTE: Labor Operation is coded to base vehicle coverage in the warranty system.
VIEW A
PLUGGED FITTING
(CONTROL VALVE)
Figure 1
1 . SEAL
2 . SPRING
3. O-RING
4 . CAP NUT
5. ELBOW
165007
CHEVROLET
CHEVROLET MOTOR DIVISION Gam®
General Motors Corporation
Technical Service Department
subject: POWER STEERING PUMP NOISE/HIGHER FLUID PRESSURE
TO: ALL CHEVROLET DEALERS
Model and Year: 1990 P3 MOTORHOMES (16000# GVW ONLY)
Dealer
Service
Bulletin
Number:
90-397-313
Section:
January 1991
Date:
313
Some of the above subject vehicles may experience higher noise due to vacuum buildup
in the power steering reservoir.
To correct this condition, it is necessary to replace the power steering reservoir cap with
a new vented cap and install a longer vent hose with a new fastening clamp.
SERVICE PARTS INFORMATION
Hose must be cut to 870mm length for proper protection of radiator from vented fluid .
Parts are currently available from GMSPO.
Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer.' They are written to inform
these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job
properly and safely . If acondition is described, DO NOTassume that the bulletin applies to yourvehicle, or that your vehicle
will have thatcondition. See your Chevrolet dealerfor information on whetheryourvehicle maybenefit from that information.
GSD 148D Rev. 12/89
Part Number Description Quantity Required
26018909 Cap 1
15654401` Hose 1,
1648216 Clamp 1
subject: AUTOMATIC/MANUAL APPLY PARKING
BRAKE WILL NOT RELEASE/LEAKING
POWER STEERING FLUID
Model and Year: 1990 P3 MOTOR HOME CHASSIS
SERVICE PROCEDURE: (Figures 1A and 1B):
2.
3 .
4.
5 .
6.
Some 1990 P3 Motor Home Chassis 16000 Lbs GVW may experience fluid leaks near the
hose clamps on the hydraulic manual apply park brake hose assembly. This will not allow
the park brake to be released. This assembly was manufactured utilizing a hose and clamp
assembly (Figure 1 A).
To correct the above condition, a new crimped hose assembly (P/N 26025331) has been
released (Figure 1 B).
DO NOT put transmission selector in "Park" position. Use Neutral. DO NOT set
manual park apply (leave "park brake" control knob in the OFF position, brake not
applied) . Ignition in the off position. Put blocks on wheels.
Remove the left front wheel well panel . Retain all fasteners and panel for the
reinstallation process. Locate the return line hose from Figure 1A. Prepare the
removal area by having a towel or rag available to catch any oil leakage from the
hose during removal.
Obtain the replacement hose (P/N 26025331) prior to removing the old hose
assembly.
Remove the clamped hose assembly, catch as much fluid as possible . Remove the O
ring seal from the steering gear. Reinstall new O ring seal (P/N 26001594). Carefully
seat O ring in steering gear seat. Install new hose (26025331) at steering gear and
finger tighten. Then install hose at relay valve ; again, finger tighten.
Torque the tube nut at the steering gear to 20-34 N.m (15-25 Ibs. ft.) and the fitting at
the valve assembly to 20-27 N.m. (15-20 lbs. ft.) (Figure 1 B) .
Bleed the power steering system. Using the procedures identified in the service
manual for power steering; purge the system of air. After completion of the bleeding
procedure reinspect the hose for any oil leaks. Retorque as required . Reinstall the
wheel well panel.
Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer," They are written to inform
these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job
properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle
will have that condition . See your Chevrolet dealer for information on whether your vehicle may benefit from that information.
GSD 1480 Rev. 11249
90-419-5 CHEVROLET Dealer Number:
Service
CHEVROLET MOTOR DIVISION Section::
General Motors Corporation Bulletin MAY 1991 Technical Service Department Date:
065024R
Corporate Bulletin No.:
NOTE : Do not put transmission in "Park" position or apply manual control valve until after
bleeding is completed .
SERVICE PARTS INFORMATION:
WARRANTY INFORMATION:
For vehicles repaired under warranty use :
Labor Operation : T7226
Labor Time: 0.7 hr.
Trouble Code: 92
Quantity
Part Number Description Required
26025331 Hose Assembly 1 (All P3 with 16,000 lb
option C7P)
26001594 0 Ring 1
Parts are currently available from GMSPO.
Relay
Valve
Assembly
Removal Figure 1 A Installation Figure 1 B
Remove relay valve
inlet pipe assembly
at tube nut and
steering gear-nut.
Remove O-ring
Steering Gear
Relay Valve
Assembly
Fitting Torque
(20-27 N-m)
Tube and Hose
Assembly
26025331
Fitting Torque
(20-34 N"m)
Note: Seat O-ring prior to Installing
hose fitting to steering gear
065024
Figure 1
CHEVROLET
CHEVROLET MOTOR DIVISION e®
General Motors Corporation
Technical Service Department
subiw: AUTO APPLY PARKING BRAKE
MAY NOT RELEASE
Model and veer: 1990-91 P3 TRUCK
Dealer
Service
Bulletin
AUTO APPLY CABLE ON 1990-91 P3 16,000# MOTORHOMES WITH C7P
SERVICE PROCEDURE:(Figure 1):
5. Torque the nut to 6 - 9 N.m. (4.5 to 6.6 lbs. ft.) .
7 . Return vehicle to holding area; service inspection work is completed.
Number:
91-240-5
5
Section:
MARCH 1991
Date:
065022
Corporate Bulletin No.:
Some 1990 - 1991 P3 Motorhomes with auto apply parking brake may not release. The
cause may be loosening of the auto apply cable and/or the auto apply control valve. Follow
the appropriate.service procedure that addresses the condition.
The auto apply control cable may loosen or pull through the attaching clip. This loosening
can be corrected by the replacement of the clip (2058447) and the installation of a new
washer (2436161).
1 . Place shift lever in park, turn ignition key to the off position . Block the wheels to
prevent vehicle movement during servicing.
2. Locate the park brake control cable under the instrument panel adjacent to the
steering column (Figure 1).
3. Remove the bolt holding the cable in place . Retain the bolt and nut for the
reinstallation procedure.
4. Remove the cable clip from the cable and discard. Utilizing a new clip (P/N 343464)
attach the cable to the bracket using the existing bolt and nut and a new washer (P/N
2436161). Align the clip so that no kinking of the cable occurs during the tightening of
the bolt and nut as shown in Figure 1 .
6. Start the engine . Verify the vehicle's transmission is 'in the neutral position and the
"park brake" Control is applied. Release the "park brake" control and observe that light
on dash goes out. Reapply the "park brake" control and observe that park brake
actuates . Also verify that park brake cable operates smoothly.
Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer." They are written to inform
these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job
properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle
will have that condition. See your Chevrolet dealer for information can whether your vehicle may benefit from that information.
GSD 148D Rev. 12189
SERVICE PARTS INFORMATION
Part Number Description Quantity
2436161 Washer 1 (all P30032 at 16,000 lb, Option C7P)
343464 Clip 1
WARRANTY INFORMATION
Labor Operation: T7216'
Labor Time: 0.2 hr.
TROUBLE CODE : 92
AUTO APPLY VALVE BRACE ON 1990 P3 16,000# MOTORHOMES WITH C7P
The auto apply control valve may loosen at the cam actuator arm . This condition can be
corrected by the installation of a brace, (P/N 15666448).
SERVICE PROCEDURE (Figure 2):
1 . Set parking brake, block wheels, ignition in the off position, and transmission in the park
position .
2. Locate the park brake control valve on the left inside frame rail adjacent to the
transmission shift control (Figure 2).
3. Remove the three bolts shown in figure 2., Discard the washers ; retain the 5/16" bolt and
nut. Obtain two new nuts and bolts for the lower mounting attachment.
4. Install the new brace (P/N 15666448) towards the transmission on the control valve so
that the brace faces inboard. Install the two new lower bolts and nuts as shown. Reinstall
the existing upper bolt and nut.
IMPORTANT Nuts and bolts must be installed as shown in Figure 2 with the nuts clamping
against the new brace .
5 . Torque the two 1/4" nuts and the 5/16" nut to 6 - 9 N.m. (4.5 to 6.6 lbs. ft).
6. With the vehicle in the park position, remove the wheel blocks, start the engine, release
the manual park brake, and cycle the auto park apply system by moving the shift lever
from park to drive. Observe that the vehicle's park brake functions properly.
7 . Turn off vehicle; put on parking brake; shift lever in park; inspect the control valve for any
hydraulic leaks; torque fitting as required.
SERVICE PARTS INFORMATION
WARRANTY INFORMATION
Labor Operation : T7217'
Labor Time : 0.5 hr.
TROUBLE CODE : 92
AUTO APPLY VALVE BRACE ON 1991 P3 16,000# MOTORHOMES WITH C7P
The auto apply control valve may loosen at the cam actuator arm. This
condition can be corrected by the installation of a brace, (P/N
15666448) .
SERVICE PROCEDURE: (Figure 3)
1 . Set parking brake, block wheels, ignition in the off position, and transmission in the park
position .
2. Remove the left hand front splash shield, save all fasteners for reinstallation. Locate the
park brake control valve on the left side above the steering gear (Figure 3).
3. Remove the three bolts shown in Figure 3. Discard the three washers, two 1/4" and one
5/16" washer. Replace the two 1/4" bolts and nuts with new hardware. Reuse the 3/16"
bolt and nut.
4. Install the new brace (P/N 15666448) on the control valve so that the brace faces
outboard. Install the two lower bolts and nuts. Reinstall the upper bolt and nut.
IMPORTANT: Nuts and bolts must be installed so that the nutsclamp against the new brace.
5. Torque the three nuts to 6 - 9 N.m. (4.5 to 6.6 lbs. ft.) .
6. Reinstall the splash shield . Reuse the fasteners ; torque to standard specifications
(figure 3).
7. With the vehicle in the park position, remove the wheel blocks . Start the engine; release
the manual park brake, and cycle the auto park apply system by moving the shift lever
from park to drive. Observe that the vehicle's park brake functions properly.
8. Turn off vehicle; put on parking brake ; shift lever in park. Inspect the control valve for any
hydraulic leaks. Torque the fittings as required .
Part Number
15666448
Description
Brace Park Brake
Quantity
1 (all P30032 at 16,000, Control
Valve option C7P)
9440148 Bolt 1/4"-20 X 2 .00" 2
(GM 280-M)
9422273 Nut 1/4"-20 2
(GM 286-M)
-4-
SERVICE PARTS INFORMATION
WARRANTY INFORMATION
Labor Operation : T7218'
Labor Time: 0.7 hr
TROUBLE CODE: 92
' NOTE: All Labor Operation are coded to base vehicle coverage in the warranty system.
Parts are currently available from GMSPO.
Part Number Description Quantity
15666448 Brace Park Brake 1 (all P30032 at 16,000, Control
Valve option C7P)
9440148 Bolt 1/4"-20 X 2.00" 2
(GM 280-M)
9422273 Nut 1/4"-20 2
(GM 280-M)
Existing
Bolt/Screw
(6-9 N-m)
Figure 1-1990 Cable Clipping
New Nuts
9422273
(6-9 N-m)
Control Valve
Assembly
Existing
Nut and Bolt
(6-9 N-m)
Assembly Note: All three brace retaining nuts and bolts must be installed
so that the nuts clamp against the new brace.
065022
Figure 2-1990 Auto Apply Brace For P30032 With C7P
7_
Existing
Nut and Bolt
(6-9 N-m)
New Nuts
9422273
(6-9 N-m)
Assembly Note: All three brace retaining nuts and bolts must be installed
so that the nuts clamp against the new brace.
065022
Figure 3-1991 Auto Apply Valve Brace For P30032 With C7P
CHEVROLET
CHEVROLETMOTOR DIVISION Gr-=
General Motors Corporation
Technical Service Department
subject: SERVICE ENGINE SOON LIGHT (CODE 22)
Model and Year :
engines for light duty trucks.
Cause:
Dealer
Service
Bulletin
1991-92 CAPRICE AND CAMARO WITH 5.01- AND 5.71- ENGINES
1991-92 ALL TRUCKS WITH 3.1 L, 4.3L, 5.OL, 5.71- AND 7.41- ENGINES
THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN 91-357-6E, DATED JUNE
1991 . THE VIN BREAKPOINTS HAVE BEEN ADDED AND THE BULLETIN NUMBERS WHICH WERE
CANCELLED SHOULD READ 91-60-6E AND 91-333-7A. ALSO THE 1992 MODEL YEAR HAS BEEN
ADDED. ALL COPIES OF 91-357-6E SHOULD BE DISCARDED.
PLANT VIN BREAKPOINT
SHREVEPORT 1 GCCSI4ZLM8177329
MORAINE 1 GNCS13ZLM2211006
PONTIAC 1 GCCT14Z5MO149156
This bulletin pertains to the 5.01- and 5 .71- engine for passenger cars and 4.3U3.1 L, 5.0U5 .7L and 7.41-
Condition Some owners of the above vehicles may comment on a Service Engine Soon Light - Code 22 -
Throttle Position Sensor low. Additional comments may include no upshift to 4th gear, no TCC,
harsh transmission shifts, or poor idle quality. These conditions may be more prevalent after
initial startup.
The above concerns may result from an intermittent electrical contact inside the Throttle
Position Sensor (TPS).
Correction : If any of the subject conditions are found, complete the following procedure :
1 . Perform the normal diagnostics per Section 6E of the Service Manual.
2 . Check TPS/ECM connectors per Dealer Service Bulletin No . 91-106-6E.
Part is currently available from GMSPO.
Use applicable labor operations and times .
Number:
Section:
92-02-6E
6E
AUGUST 1991
Date :
136514R
Corporate Bulletin No . :
3. If no problems are found using the normal 6E diagnostics or the bulletin, replace the TPS
with a new TIPS kit, P/N 17112679 per the procedure in Section 6E of the Service Manual .
The new TPS will have a yellow dot at the connector area for easier identification .
Note : The lack of 4th gear, no TCC and harsh transmission shift concerns are only associated on truck
applications with the HYDRA-MATIC 41-80-E (4 speed automatic) electronic transmission .
Chevrolet bulletins are intended for use by professional technicians, NOTa "do-it-yourselfer," They are written to inform these technicians of conditions that
mayoccur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment,
tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your
vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information.
GSD 148D Rev. 12/89
CHEVROLET
CHEVROLET MOTOR DIVISION Gas
General Motors Corporation
Technical Service Department
Subject: BRAKE SQUEALINOISE
Model and Year : 1976-91 P3 MOTOR HOMES EQUIPPED
WITH 4-WHEEL DISC BRAKES (RPO JF9)
THIS BULLETIN REVISES DEALER SERVICE BULLETIN NO. 91-151-5, DATED JANUARY 1991 .
REPLACEMENT OF BOTH FRONT AND REAR LININGS HAS BEEN SPECIFIED. ALL COPIES OF
91-151-5 SHOULD BE DISCARDED.
A new brake lining service kit is available that contains brake pads constructed of a new compound
developed to reduce brake noise and squeal . It is important to understand that the new pad material will not
totally eliminate brake noise. It can, however, reduce the noises to a level which is more acceptable .
The new brake lining service kit, GM Part Number 15649295 contains all components necessary to replace
either the front or rear brake linings. To better resolve brake squeal and maintain the vehicle's originally
designed brake balance (front to rear), both front and rear linings should be replaced at the same time. The
new brake pads can be identified by the CBD812 edge code printed on the side of the pad material .
SERVICE PARTS INFORMATION:
Part Number Description
15649295 Brake Lining
Service Kit
Note : Use one kit per axle.
Parts are currently available from GMSPO.
WARRANTY INFORMATION:
For vehicles repaired under warranty use :
Labor Operation Location
H0042 Front
H0043 Rear
Use applicable labor time guide for labor hours.
Dealer
Service
Bulletin
Number :
REVISED
91-151 A-5
5
Section:
AUGUST 1991
Date :
965016R
Corporate Bulletin No.:
A5
ASE No.:
Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer ." They are written to inform these technicians of conditions that
may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment,
tools, safety instructions, and know-how to do ajob properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your
vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information.
GSD 148D Rev. 12/89
~CHEVROLET Dealer
GeO Service
Bulletin CHEVROLET MOTOR DIVISION
General Motors Corporation
Technical Service Department
Subject: CHANGE IN BRAKE EFFECTIVENESS AFTER DISC BRAKE ROTOR
REFINISHING/PAD REPLACEMENT
Model and Year: ALL PASSENGER CARS
ALL LIGHT DUTY TRUCKS
TO: ALL CHEVROLET DEALERS
Number :
Section :
91-133-5
5
December 1990
Date:
075003R
Corporate Bulletin No . :
THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO.
90-316-5, DATED AUGUST 1990 . INFORMATION HAS BEEN ADDED REGARDING
HUB AND ROTOR CLEANING, PROPER TORQUING TECHNIQUE., REVISED MACHINING
TABLE, CHANGE SPECIFICATION FOR MAXIMUM SCORINGING DEPTH. THE
1991 MODEL YEAR WAS ALSO ADDED. ALL COPIES OF 90-316-5 SHOULD BE DISCARDED
.
Some comments have been received about a change in preceived braking effectiveness
which occurs after rotors have been refinished and/or disc brake pads have been
replaced. New lining materials have been formulated for increased lining life and to reduce
brake squeal . Also, Federal regulations currently prohibit the use of asbestos in Original
Equipment Manufactured (O .E.M .) front disc brake linings, and will totaly ban asbestos
from all O.E .M. brake linings in the near future . Due to these changes, initial rotor surface
finish is more critical than in the past, and is required for good brake performance .
Following are some recommended actions/procedures to assure proper performance of
the brake systems on all vehicles after rotor and/or pad service has been performed:
When performing routine brake maintenance such as replacing worn disc brake pads
or shoes, DO NOT refinish disc brake rotors or drums unless :
A. There is a brake pulsation condition present, and this pulsation is found to be,
caused by the brake rotors or drums, or
B. The rotors and/or drums are excessively scored . Surface scoring that does not
' exceed 1 .2MM (0 .050 in .) on rotors or drums should not affect brake operation .
Before removing rotors from the hub assembly, mark the rotor and on wheel stud
so that the rotor may be re-installed in the same position .
Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer, They are written to inform
these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job
properly and safely . If a condition is described, DO NOTassume that the bulletin applies to your vehicle, orthat your vehicle
will have thatcondition. See your Chevrolet dealerfor information on whether yourvehicle maybenefitfrom that information .
GSD 148D Rev. 12/89
If rotors are removed, it is very important that rust and scale be removed from the rotor and
hub mating surfaces . Failure to do so may introduce excessive lateral runout when the
rotor is mounted on the brake lathe, or when the rotor is re-installed to the hub.
2. When refinishing disc brake, rotors, it is important that the brake lathe be in good
operating condition and that all tools or bits are sharp. Recommended vibration
dampeners and/or adaptors should be used and should be clean and free of nicks
(remember, 1988-91 W models require the use of an adaptor, J37160, because of the
two-piece design). The following table shows the recommended procedure for rotor
machining :
It is important that a rough and a finish cut be made . All brake lathes use a single-point
cutting tool which is not capable of giving the necessary surface finish . A SECONDARY
FINISHING OPERATION MUST BE PERFORMED TO OBTAIN THE NECESSARY
SURFACE FINISH .
An acceptable finish can be obtained using the Ammco Model 8350 Safe Swirl Disc Rotor
Grinder, or equivalent, using 120 grit sandpaper and sanding each rotor surface with
moderate pressure for a minimum of 60 seconds with the rotor turning at 150 RPM. An
alternate method is to use a sanding block with 150 grit sandpaper. With the rotor turning
at approximately 150 RPM, sand each side for a minimum of 60 seconds using moderate
pressure .
After the rotor has been sanded, the surfaces must be cleaned with a solvent such as
brake cleaning, denatured alcohol, or equivalent .
THE FINISHED ROTOR SURFACE SHOULD BE AS CLOSE TO THAT OF A NEW
ROTOR AS POSSIBLE . FAILURE TO OBTAIN THE BEST POSSIBLE ROTOR FINISH
WILL AFFECT INITIAL BRAKING PERFORMANCE.
CAUTION : ROTORS OR DRUMS SHOULD ALWAYS BE REPLACED IF TURNING WILL
RESULT IN A ROTOR OR DRUM THAT DOES NOT MEET MANUFACTURER SPECIFICATIONS
FOR MINIMUM ROTOR THICKNESS OR MAXIMUM DRUM DIAMETER.
NOTICE : When re-installing tire and wheel assemblies, it is very important that proper
procedures be followed when installing and torquing the wheel nuts:
91-133-5
A. Finger start all wheel nuts.
B. Tighten wheel nuts .to specified torque (use the "star," or alternating nut pattern)
using a torque wrench. DO NOT USE AN IMPACT WRENCH. UNEVEN AND/OR
EXCESSIVE TORQUING OF THE WHEEL NUTS HAS BEEN FOUND TO
DISTORT ROTORS, RESULTING 1N PREMATURE CUSTOMER COMEBACKS
FOR BRAKE PULSATION
ROUGH CUT FINISH CUT
Spindle Speed 150 RPM 150 RPM
Depth of Cut (per side) 0.127mm (0 .005") 0.051 mm (0 .002")
Tool Cross Feed per Rev 0 .152mm - 0.254mm 0.051 mm (0.002")Max
(0 .006" - 0.010")
Vibration Damper Yes Yes
Sand Rotors-Final Finish No Yes
3. After brake pads have been replaced and/or rotors have been refinished, it is
recommended that the new braking surfaces be broken in, or burnished, to properly
seat them. This can be accomplished by making 20 stops from 30 mph, using medium
to firm pressure . Take care to avoid overheating the brakes.
4 . It is strongly recommended that the correct, specified General Motors replacement
part(s) be used when servicing G.M . vehicles . General Motors does not test non-G.M.
parts for proper performance on G.M . vehicles . Therefore, the use of non-G.M . parts
may result in unacceptable vehicle performance . It is also important that the correct
G M. part(s) be used in the correct G.M . application. For example, some 'A' model
disc brake pads ('A' Heavy) will fit on 'C and H' models, but will not provide the same
performance as the pads specified for use on C and H vehicles . It may seem
preferable to stock fewer brake pad part numbers, but customer dissatisfaction may
result if vehicle performance is affected .
91-133-5
CHEVROLET
CHEVROLET MOTOR DIVISION
General Motors Corporation
Technical Service Department
Subject: AUTOMATIC TRANSMISSION
DIAGNOSIS CHARTS UPDATED
Model and Year:
Dealer
Gem Service
Update
Bulletin
1991 C/K, R/V, P AND G TRUCKS WITH
4L80-E/4L80-EHD AUTOMATIC TRANSMISSION
SERVICE UPDATE
BULLETIN COVERS:
HYDRA-MATIC 4L80-E/4L80-EHD Transmission updates occurring after Service Manual
printing .
LIGHT DUTY TRUCK SERVICE MANUAL UPDATES:
Automatic Transmission / Diagnosis Information:
Range Reference Chart has been revised. (Figure 1)
Wiring Diagram has been revised. (Figure 2)
Number :
91-210-7A
Section:
7A
FEBRUARY 1991
Date :
177107R
Corporate Bulletin No. :
Remove Notice under Torque Converter Clutch (TCC) Diagnosis:
Notice says: Do not bench test the TCC Solenoid using an automotive type battery.
Accidentally crossed wires will damage the internal diode of the Solenoid. (This notice
does not apply to the 4L80-E Transmission .)
Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer," They are written to inform
these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job
properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle
will have that condition . See your Chevrolet dealer for information on whether your vehicle may benefit from that information.
GSD 1481 Rev. 12189
HYDRA-MATIC 4L80-E - GEAR RATIOS
FIRST 2 .48 FOURTH .75
SECOND 1 .48 REVERSE 2 .08
THIRD 1 .00
*HOLDING BUT NOT EFFECTIVE
ON - SOLENOID ENERGIZED
OFF - SOLENOID DE-ENERGIZED
0 THE SOLENOID'S STATE FOLLOWS A SHIFT PATTERN WHICH DEPENDS UPON VEHICLE
SPEED AND THROTTLE POSITION . I T DOES NOT DEPEND UPON THE SELECTED GEAR .
NOTE: DESCRIPTIONS ABOVE EXPLAIN COMPONENT FUNCTION DURING ACCELERATION.
Figure 1- Range Reference Chart
RANGE GEAR
SOLENOID
OA
SOLENOID
OB
FOURTH
CLUTCH
OVERRUN
CLUTCH
OVERDRIVE
ROLLER
ROLLER
FORWARD
CLUTCH
DIRECT
CLUTCH
FRONT
BAND
INTERMEDIATE
SPRAG
CLUTCH
INTERMEDIATE
CLUTCH
LO
ROLLER
CLUTCH
REAR
BAND
- ON OFF HOLDING
REVERSE ON OFF HOLDING APPLIED APPLIED
1st ON OFF HOLDING APPLIED * HOLDING O 2nd OFF OFF HOLDING APPLIED HOLDING APPLIED OVERRUNNING
3rd OFF ON HOLDING APPLIED APPLIED OVERRUNNING APPLIED OVERRUNNING
4th ON ON APPLIED OVERRUNNING APPLIED APPLIED OVERRUNNING APPLIED OVERRUNNING
1st ON OFF APPLIED HOLDING APPLIED * HOLDING
D 2nd OFF OFF APPLIED HOLDING APPLIED HOLDING APPLIED OVERRUNNING
3rd
K2nd
OFF ON APPLIED HOLDING APPLIED APPLIED OVERRUNNING APPLIED OVERRUNNING
1st ON OFF APPLIED HOLDING APPLIED * HOLDING
OFF OFF APPLIED HOLDING APPLIED APPLIED HOLDING APPLIED OVERRUNNING
131 ON OFF APPLIED HOLDING APPLIED " HOLDING APPLIED
2nd OFF OFF APPLIED HOLDING APPLIED APPLIED HOLDING APPLIED OVERRUNNING
3-
,Ilililil~lilVil~ ~I.I~~I
pppp
II~I~UI1I11111 1
r~sa
(B) SOLENOID "B" GROUND-GREEN
(A) SOLENOID "A" GROUND-BLUE
~- (C) +12V SHIFT SOLENOIDS-RED.
(D) PSM-BLACK
\~C (E) PSM-WHITE
\\\r (F) PSM-BLUE
L (M) FORCE MOTOR-GREEN
(L) FORCE MOTOR-BLUE
/(K) 12V PWM SOLENOID-WHITE
(J) PWM SOLENOID GROUND-BLACK
(H) +5V TEMP. SENSOR-RED
(G) TEMP . SENSOR GROUND-GREEN
Figure 2 - Wiring Diagram
CHEVROLET Dealer
Ge® Service
Bulletin CHEVROLET MOTOR DIVISION
General Motors Corporation
Technical Service Department
Subject : ELECTRONIC AND ELECTRO-MECHANICAL
INSTRUMENT CLUSTERS
Model and Year : ALL LIGHT DUTY TRUCKS
TO : ALL CHEVROLET DEALERS
Chevrolet and AC Delco have formed a joint program designed to help dealers locate
exchange instrument clusters . A service called the "Instrument Cluster Locator Line" has
been established .
For your regular service needs, you should contact the nearest AC Delco Service Center.
If they do not have the required cluster, you should then use the Instrument Cluster
Locator Line. To do so, call the Locator Line operator at (313) 974-0497 between 7 :30 and
4:30 Eastern Standard Time. The following information is required :
the name of the AC Delco Service Center previously contacted
the part number of the unit needed
your dealer name, address and telephone number
the make and body style of the vehicle being repaired .
Number :
91-150-8C
8C
Section :
January 1991
Date :
068302
Corporate Bulletin No . :
The operator will then locate another AC Delco Service Center which has the required
cluster and call you back that same day to let you know where the part can be found.
You can then order the part directly from that Service Center. The part will be shipped
within 24 hours and you will receive it within 48 hours. Please note that the Instrument
Cluster Locator Line Program should only be used if the electronic or electro-mechanical
cluster is not available from your local AC Delco Service Center.
Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer." They are written to inform
these technicians of conditions that mayoccur on some vehicles, or to provide information that could assist in the proper
service of avehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job
properly and safely . If a condition is described, DO NOTassume that the bulletin applies to your vehicle, or that your vehicle
will have that condition. See your Chevrolet dealerfor information onwhether your vehicle maybenefit from that information.
GSD 148D Rev. 12/89
=':7CHEVROLET Dealer
Ge® Service
Bulletin
CHEVROLET MOTOR DIVISION
General Motors Corporation
Technical Service Department
subiect: DETONATION AND/OR EXHAUST ODOR
Model and Year : 1990 C/K, R/V, G AND P TRUCK
WITH 7.4L ENGINE
Condition : Some owners of 1990 trucks with the 7.4L engine may comment of either
detonation at highway speeds or exhaust odor (sulfur smell) at idle .
Cause: The original spark advance and idle calibration may generate detonation or
sulfur odor comments for a few isolated conditions.
Correction : On trucks where these conditions can not be repaired using normal service
procedures, a revised calibration PROM should be installed (See below) .
Parts are expected to be available on June 3, 1991 . Until then normal part orders will not be
accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. SPO will
make every effort to obtain parts . All parts will be placed on 400 control to waive VIP
surcharges. However, the part will be shipped premium transportation at dealer's expense.
All other order types will be cancelled as incorrectly ordered while the 400 control is in place.
Note : These PROMS SHOULD NOT BE USED on the Chevy "S .S."
Labor Operation Number: T0500
Labor Time : .6 Hour
Trouble Code : 92
Number:
Section:
90-421-6E
6E
_MAY 1991
Date :
136511
Corporate Bulletin No . :
Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer." They are written to inform
these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle . Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job
properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle
will have that condition . See your Chevrolet dealer for information on whether your vehicle may benefit from that information .
GSD 148D Rev. 12/89
Part Emission PROM SCANNER
Number System Trans. Broadcast I.D .
16165446 NA4 (above M40 (Auto) AYKK 5451
8600 GVW)
16165447 NA4 (above M20 (Manual) AYKL 5461
8600 GVW)
CHEVROLET Dealer GC® Service
Bulletin
CHEVROLET MOTOR DIVISION
General Motors Corporation
Technical Service Department
subject: INOPERATIVE SPEEDOMETER
Model and Year : 1989-90 P3 (MOTOR HOME) CHASSIS
TO : ALL CHEVROLET DEALERS
Number:
Date :
Some 1989-1990 P3 motor home chassis (32) and commercial van chassis (forward
control chassis - model 42) may experience inoperative speedometers . This condition can
be caused by either inadequate engagement of the upper speedometer cable or a broken
lower speedometer cable tip .
To correct, it is necessary to install either a new upper or lower speedometer cable. The
new upper speedometer cable has a longer shaft core tip to provide full engagement of the
speedometer core tip between the Vehicle Speed Sensor (VSS) and speedometer head
(part of the instrument cluster) . The lower speedometer cable has a metal tip replacing a
plastic tip to help prevent tip breakage.
Vehicle manufacturing breakpoint is listed below :
1GBJP37N7L3321236
Prior to performing the installation procedures, verify if the condition experienced is the
result of inadequate engagement of the upper speedometer cable. If an inadequate
engagement condition is present, replacement of the upper speedometer cable is
required . Inspect the lower speedometer cable for a broken tip at the speed sender
generator. If broken, replacement of the lower speedometer cable is required .
INSTALLATION INSTRUCTIONS:
UPPER SPEEDOMETER CABLE REMOVAL AND REPLACEMENT (see Figure 1):
1 . Disconnect the negative battery connection.
90-368-8C
8C
Section :
October 1990
063305R
Corporate Bulletin No . :
2 . Set park brake and put transmission lever in park.
3. Disconnect and remove the upper speedometer cable from the speedometer head in
the instrument cluster.
Chevrolet bulletins are intended for use by professional technicians, NOTa "do-it-yourselfer, They are written to inform
these technicians of conditions that mayoccur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job
properly and safely . If a condition is described; DO NOTassume thatthe bulletin appliesto your vehicle, or that yourvehicle
will have thatcondition. See your Chevrolet dealer for information on whetheryourvehicle may benefitfrom that information.
GSD 148D Rev. 12MO
90-368-8c
4. On Commercial vehicles, disconnect the opposite end of the cable from the road
speed sender generator located underneath the vehicle (outboard of the left hand
frame rail and in back of the front axle). On Motor Homes, disconnect the opposite end
of the cable located in the left hand frame rail across from the transmission .
5. Install the new upper speedometer cable into the instrument cluster and connect to
speedometer head .
6. On Commercial or Motor Home vehicles, reconnect the opposite end of the cable to
the vehicle speed sensor (VSS) . Route and attach cable to avoid kinking, chafing or
high temperature areas . Clip at positioning cable .
7 . Reconnect negative battery connection.
8. Check for proper operation of speedometer.
LOWER SPEEDOMETER CABLE REMOVAL AND REPLACEMENT (see Figure 1) :
1 . Disconnect the negative battery connection .
2. Inspect road speed sender generator for broken plastic speedometer cable tip. If
broken, remove broken piece prior to installing new cable.
3. Disconnect the lower cable from the vehicle speed sensor (VSS) .
4. Disconnect the opposite end of the cable at the transmission and remove cable .
5. Reconnect the lower speedometer case to the VSS.
6 . Reconnect cable at transmission end . Route cable to avoid kinks or chafing.
7 . Reconnect negative battery connection .
8 ., Check operation of speedometer.
SERVICE PARTS INFORMATION :
Part No. Description Qty. P3 Model
16154975 Upr Speedo , Cable Asm. 1 Commercial (42) with Gas Engines.
16154985 Upr Speedo Cable Asm. 1 Motor Home (32) with Gas Engines .
16155035 , Lwr Speedo Cable Asm. 1 (*) Motorhome(32)/Commercial
(42) with Gas Engines, Auto .
Trans . & Power Disc Brakes.
16155045 Lwr Speedo Cable Asm. (') Commercial (42) with Gas
Engines & Manual Trans .
16155055 Lwr Speedo Cable Asm. 1 (') Motorhome (32)/Commercial
(42) with Gas Engines & auto.
Trans. & Hydraulic Brakes.
P/N 16154975 Use with RPO's LB4/1-05/1-19.
P/N 16154985 Use with RPO 1-19.
P/N 16155035 Use with RPO's 1-134/1-05/1-19 and M40 and JB7/JB8.
P/N 16155045 Use with RPO's LB4/1-05 and M20.
P/N 16155055 Use with RPO's 1-05/1-19 and M40 and JF9.
RPO CODES:
LB4 = 4.31- Gas Eng. M40 = 3-Spd . Auto. Trans.
1-05 = 5.71- Gas Eng. JB7 = Power Disc, Drum 8400 Lbs.
1-19 = 7.41- Gas Eng. JB8 = Power Disc, Drum 10000 Lbs.
M20 = 4-Spd. Man. Trans . JF9 = Hyd. Brake, 4 Wheel Disc
MODEL CODES:
32 = Motor Home Chassis
42 = Commercial - Forward Control Chassis
Parts are currently available from GMSPO.
WARRANTY INFORMATION
For vehicles repaired under warranty use:
Labor
Operation Description
90-368-8C
N4382 R & R Upper Speedometer Cable
N4383 R & R Lower Speedometer Cable Labor Time
Use applicable Labor Time Guide for labor hours.
1990 - The vehicle speed sensor is located on the LH
frame rail in the speedometer cable.
1991-1994 - The cruise control receives its signal from
the drac module located on the LH side of the steering'
column.
90-368-8C
Figure 1
P/N 16154975 Use with RPO's 1-134/1-05/1-19 .
P/N 16154985 Use with RPO L19.
P/N 16155035 Use with RPO's 1-134/1-05/1-19 and M40 and JB7/JB8.
P/N 16155045 Use with RPO's 1-134/1-05 and M20.
P/N 16155055 Use with RPO's 1-05/1-19 and M40 and JF9.
RPO CODES:
LB4 = 4.31- Gas Eng. M40 = 3-Spd. Auto . Trans .
1-05 = 5 .71 Gas Eng. JB7 = Power Disc, Drum 8400 Lbs.
1-19 = 7 .41- Gas Eng. JB8 = Power Disc, Drum 10000 Lbs.
M20 = 4-Spd. Man. Trans. JF9 = Hyd. Brake, 4 Wheel Disc
MODEL CODES:
32 = Motor Home Chassis
42 = Commercial - Forward Control Chassis
Parts are currently available from GMSPO.
WARRANTY INFORMATION
For vehicles repaired under warranty use :
Labor
Operation Description
Use applicable Labor Time Guide for labor hours .
90-368-8C
N4382 R & R Upper Speedometer Cable
N4383 R & R Lower Speedometer Cable Labor Time
1990 - The vehicle speed sensor is located on the LH
frame rail in the speedometer cable.
1991-1994 - The cruise control receives its signal from
the drac module located on the LH side of the steering'
column.
90-368-8C
10 FRT
FRAME RAIL
REINSTALL TO
TRANSMISSION
LOWER CABLE
PARK BRAKE CABLE / / VEHICLE SPEED SENSOR
Figure 1
CHEVROLET
CHEVROLET MOTOR DIVISION Gea
General Motors Corporation
Technical Service Department
subject: NEW STYLE HOSE CLAMP
Model and Year :
SERVICE PROCEDURE:
1983-92 ALL C/K AND 1987-92 R/V TRUCKS
WITH 4.3L, 5.OL, 5.7L, 6.2L, 7.4L ENGINES
Dealer
Service
Bulletin
Number :
92-03-68
6B
Section:
AUGUST 1991
Date :
166201
Corporate Bulletin No .:
A new design hose clamp will be used in production starting , with the 1992 model year on C/K trucks . Usage
of this clamp will expand to include other models in the 1993 model year. The Mubea constant tension hose
clamp was designed to reduce the amount of coolant leakage from radiator and heater hoses.
With the previous design, screw type clamps, it is difficult to maintain a constant load on the hose connection .
Some of the load is lost under certain temperature changes . The Mubea clamp exerts a relatively even and
constant pressure that is maintained under varying temperature conditions.
o The- Mubea clamp must be installed on a hose which will be put on to a clean, dry, paint free surface. If
lubrication is necessary for assembly, only GM lubricant P/N 998562 may be used.
9 Production of trucks with the clamp began 02/91, starting with the water pump and radiator
connections. The heater hoses will follow in some applications .
If the vehicle was originally built with Mubea clamps, the clamp should be replaced with the same P/N
Mubea clamp and not a screw type hose clamp.
9 Also if the vehicle was originally built with screw/worm type clamps, the clamps should be replaced
with screw/worm clamps.
Note: Standard pliers or hose clamp pliers will not work well on the new style clamp. Various tool companies
have developed special pliers to install and remove these hose clamps. Some companies may have a
plier available that is effective in removing the larger size clamps but may not open wide enough to
accommodate the clamp once it is off the hose and relaxed. Do not compress the clamp
(permanently) to make the tool fit it, since this will decrease the effectiveness of the clamp. GMC does
not endorse any specific tool or company. Check with local sources to determine availability.
Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer," They are written to inform these technicians of conditions that
may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment,
tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your
vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information.
GSD 148D Rev. 12189
PARTS INFORMATION:
Mubea clamps will be used in the following applications :
Note : The clamp's size is stamped on the tab of the clamp.
Parts are currently available from GMSPO.
WARRANTY INFORMATION:
For vehicles repaired under warranty use :
Labor Operation: J3340
Size Part Number Application
27mm 10108255 Heater Hoses
24mm 10146975 Heater Hoses
42mm 15671833 Radiator/Water Pump Hoses
50mm 10108249 Radiator/Water Pump Hoses
55mm 156,71832 Radiator/Water Pump Hoses
~7 CHEVROLET Dealer
. Ge® Service
Bulletin CHEVROLET MOTOR DIVISION
General Motors Corporation
Technical Service Department
subject: CRUISE CONTROL CABLE REPLACEMENT
Model and rear : 1990-91 P3 MODELS
TO: ALL CHEVROLET DEALERS
A replacement cruise control servo cable for 1990 and 1991 P3 models with factory
installed cruise control has been released by GMSPO. It will no longer be necessary to
purchase a module and cable assembly if just a cable is required (see Figure 1) .
The part number for a cruise control servo cable without the module for the P3 models
mentioned is 25075767.
Parts are currently available from GMSPO.
Number :
91-137-9
9
Section
Dece. mber 1990
Date :
069001
Corporate Bulletin No.:
Chevrolet bulletins are intended for use by professional technicians, NOT a°do-jtyyourselfer." They are written to inform
these technicians of conditions that mayoccur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job
properly and safely . If a condition is described, DO NOTassume that the bulletin applies to your vehicle, or that your vehicle
will have that condition. See your Chevrolet dealer for informationon whetheryourvehicle maybenefit from that information.
GSD 148D Rev. 12/89
replacement cable 92 -
93 -
94 -
25075767
25140500
25140187
module assembly 90-92-25075766
93 -25140082
94 -25075219
.137-9
Cruise Control Module/Cable
P-3 Motorhome Chassis
Figure 1 069001
~CHEVRDLET
CHEVROLETMOTOR DIVISION a®
General Motors Corporation
Technical SKvl e Department
subject: REUSABLE BOTTOM PAN SEAL
Model and Year:
TRANSMISSION APPLICATIONS :
1991-92 HYDRA-MATIC 41-80-E/4L80-EHD (MT1)
TRANSMISSION MODELS:
All Models
1991-92 C/K, RN, G AND P3 TRUCK WITH
41-80-E/4L80-EHD AUTOMATIC TRANSMISSION
Service Information : (Figure 1)
The HYDRA-MATIC 41-80-E transmission bottom
pan seal (29) is REUSABLE. When removing the
bottom pan (28), it is recommended to inspect the
seal for any possible leak points that may cause
future concerns:
" Tears in the rubber bead.
" Missing torque limiters or washers.
Broken carrier seal.
If no signs have been found, then clean off seal
with a clean soft cloth. Clean case and pan areas
with part solvent before reinstalling seal.
Dealer
Service
Update
Bulletin
SUBJECT:
Reusable Bottom Pan Seal
(Service Manual Information)
VEHICLE APPLICATIONS:
C/K, RN, and P- Trucks, G-Van
Figure 1
Number:
ASE No.:
92-12-7A
7A
Section:
SEPT 1991
Date:
177123
Corporate Bulletin No.:
A2
SERVICE UPDATE
27 BOLT, HEX FLANGE HD (PAN TO CASE)
28 PAN, TRANSMISSION OIL
29 SEAL, TRANS. OIL PAN
Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer .' They are written to inform these technicians of conditions that
may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment,
tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your
vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information.
GSD 148J Rev. 12189
4,D7 CHEVROLET
CHEVROLET MOTOR DIVISION Ge
General Motors Corporation
Technical Service Department
Sublecr INCORRECT OR ERRATIC OIL PRESSURE READINGS
Model and Year: 1990-93 ALL LIGHT DUTY TRUCKS
Owners of some 1990 through 1993 light duty trucks may comment that the oil pressure dash gage reads
high, has erratic movement or is inoperative.
The internal resistance wire in the oil pressure sensor may not be properly supported, resulting in an
intermittent open condition .
Service Procedure:
Check for normal causes of high oil pressure gage readings (high resistance or open circuit), such as a poor
ground path caused by loose sensor mounting, oil cooler adapter loose, or poor electrical connections. If no
cause can be found, replace the oil pressure sensor following the procedure below.
1 . Disconnect the negative battery cable.
2. Remove the wiring harness connector from the oil pressure sensor.
3. Remove the oil pressure sensor.
4. Install the new oil pressure sensor.
5. Connect the wiring harness connector to the oil pressure sensor.
6. connect the negative battery cable.
Parts Information :
Dealer
Service
Bulletin
. New Oil Pressure Sensor Part Numbers for the 1990-1993 models are:
Number :
ASE No . :
93-s7-6A
6A
Section :
NOV 1992
Date:
268304
Corporate Bulletin No . :
A1, A8
COPYRIGHT 1992 " CHEVROLET MOTOR DIVISION " GENERAL MOTORS CORPORATION " ALL RIGHTS RESERVED
Chevrolet bulletins are intended for use by professional technicians, NOTa '.do-it-yo*urselfer They are written to inform these technicians of conditions that
may occur on some vehicles, or to provide information that could assist in .the proper service of a vehicle . Properly trained technicians have the equipment,
tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your
vehicle, or that your vehicle will have that condition . See your Chevrolet dealer for information on whether your vehicle may benefit from that information .
GSD 148D Rev. 12189
En ine
Model Engine(s) VIN Codes New P/N Replaces
10201490 1647135 -90/91
S/T L38/LN8/L35 A,E,W 10201490 10096178-92/93
10201491 1647136 -91/92
1-1-2/1-134 R,Z 10201491 10096179-92/93 .
10201496 1647135 -90/91
M/L LN8/L35/1-134 E,W,Z 10201490 10096178-92/93
Parts are currently available from GMSPO
Warranty Information:
For vehicles repaired under warranty use labor operation N2220.
Engine
Model Engines) VIN Codes New P/N Replaces
10201489 10068563-90/91
C/K All Gas Z,H,K,N 10201489 10137652-92/93
10201489 10068563-90/91
All Gas Z,H,K,N 10201489 10137652-92/93
10201489 10068563-90/91
All Gas K,N 10201489 10137652-92/93
10201489 10068563-90/91
P (60 psi) All Gas Z,K,N 10201489 10137652-92/93
P (80 psi) All Gas Z,K,N 10201490 10096178-92/93
4D7 CHEVROLET
CHEVROLETMOTOR DIVISION Ge®
General Motors Corporation
Teohntcal Service Department
Subject:
Model and Year :
NEW DESIGN SPARK PLUGS
1991 ALL PASSENGER CARS
AND TRUCKS WITH CPC GAS ENGINES
Kent-Moore
SPX Corporation
39784 Little Mack
Roseville, MI 48066-2298
Fax : 313-774-9870
Dealer
Service
Bulletin
REVISED
91-234A-OB
Number:
oB
Section:
JULY 1992
Date:
166001R
Corporate Bulletin No.:
A1, A8
ASE No.:
THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN 91-234-0B, DATED
MARCH 1991 . UPDATED TOOL INFORMATION IS BEING PROVIDED. ALL COPIES OF 91-234-OB
SHOULD BE DISCARDED.
In 1991 GM introduced a new design spark plug for use in all trucks equipped with gas engines. These new
design spark plugs have a ceramic insulator which is approximately, 1 /8 inch longer than the insulator used in
previous model years.
The longer length spark plugs, which conform to S.A.E. and I.S.O. Engineering guidelines, magnify the
problem of cracked insulators because currently, most spark plug sockets are not of sufficient length to
properly engage the shell hex. If the spark plug shell hex is not fully engaged in the spark plug socket
wrench, the socket may cock at an angle and cause insulator cracking and/or breakage during plug
installation or removal.
When servicing these new design spark plugs, make sure that the spark plug socket being used is deep
enough to accommodate the longer length insulator. The spark plug socket wrench should conform to the
proposed S.A.E. and I.S.O. world standards for spark plug socket wrenches. Spark plug socket wrenches
that conform to these standards are designed to accept 'the lengthened spark plugs and allow full
engagement of the hex nut on the shell of the spark plug.
Use of a spark plug socket which is NOT deep enough may result in the ceramic insulator becoming cracked
above the spark plug shell. -
Note: SOME CRACKS IN THE INSULATOR MAY NOT BE VISIBLE. SUCH CRACKS MAY LATER CAUSE
A SPARK PLUG TO MISFIRE. SPARK PLUG MISFIRES ARE OFTEN MISDIAGNOSED AS A
SLIPPING TRANSMISSION, DEFECTIVE TORQUE CONVERTER CLUTCH, ENGINE IMBALANCE,
OR MALFUNCTIONING FUEL SYSTEM.
To prevent insulator damage, it is recommended that the proper spark plug socket wrench be used when
removing or replacing spark plugs. One such spark plug socket is the Kent-Moore J-39358 spark plug
socket. The tool is available from Kent-Moore. For ordering information call 1-800-345-2233 or write:
Chevrolet bulletins are intended for use by professional technicians, NOTa 'do-it-yourselfer .' They are written to inform these technicians of conditions that
may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment,
tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your
vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information.
GSD1480 Rev. 12/89

CHEVROLET MOTOR DIVISION
General Motors Corporation
Service Oaparlmanr
CHEVROLET
SERVICE
Subject: ELECTROSTATIC DISCHARGE DAMAGE
Model and Year: 1988 UP PASSENGER AND LIGHT DUTY TRUCKS
WITH AN ELECTRONIC CONTROL MODULE (ECM)
TO: ALL CHEVROLET DEALERS
Chevrolet
Dealer
Service
Bulletin
Number:
Section:
Date :
88-283-6E
6E
Please add the following information to 6E Section "A"Diagnostic Charts/Trouble Codes,
and to Section "C1 " Electronic Control Module and Sensors .
NOTICE : To prevent possible Electrostatic Discharge damage: ,
- Do Not touch the ECM connector pins or soldered components on the
ECM circuit board .
- When handling a PROM, CAL-PAK or Mem-Cal, Do Not touch the component
leads, and Do Not remove integrated circuit from carrier.
Electronic components used in control systems are often designed to carry very low
voltage, and are very susceptible to damage caused by electrostatic discharge . It is
possible for less that 100 volts of static electricity to cause damage to some electronic
components . By comparison, it takes as much as 4,000 volts for a person to even feel
the zap of a static discharge.
There are several ways for a person to become statically charged . The most common
methods of charging are by friction and by induction . An example of charging by friction
is a person sliding across a car seat, in which a charge of as much as 25,000 volts can
build up. Charging by induction occurs when a person with well insulated shoes stands
near a highly charged object and momentarily touches ground.
Charges of the same polarity are drained off, leaving the person highly charged with the
opposite polarity. Static charges of either type can cause damage, therefore, it is important
to use care with handling and testing electronic components.
Chevrolet bulletins are intended for use by professional technicians, NOTa 'do-it-yourselfer .'They are written to inform these technicians of conditions that
mayoccur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment,
tools, safety instructions, and know-how to do a job properly and safety. If a condition is described, DO NOT assume that the bulletin applies to your
vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information.
GSD 148D Rev. 12189
A
A. INSTRUMENT CLUSTER. GASOLINE ENGINE
B. INSTRUMENT CLUSTER. DIESEL ENGINE
Lam' CHEVROLET
CHEVROLETMOTOR DIVISION Gee
Teehniod ServiceDeparhnent
subject: FACTORS THAT AFFECT FUEL ECONOMY
Model and Year: ALL YEARS ALL MODELS
BACKGROUND INFORMATION:
FACTORS THAT AFFECT FUEL ECONOMY:
We Ratio
Dealer
Service
Bulletin
93-96-6C
6C
FEB. 1993
Dar.:
306502
CamBuAelln No. :
A1 . A8
ASENo. :
EPA fuel economy estimates are posted on the fuel economy label of all new vehicles. The only intended use of these
values is for comparison among the different vehicles. Fuel economy estimates are generated from data taken during a
laboratory test using pre-production prototype vehicles underextremely controlled conditions using a professional driver,
with the vehicle operating on an instrument similarto atreadmill. The comparisons of current vehicle fuel economy to the
EPA fuel economy estimates is a misuse of the information and should be discouraged.
The EPA GAS MILEAGE GUIDE, available at each dealership, points out that the actual mileage when driving a vehicle
may differconsiderably from the estimated mileage. The guide also describes how vehicles are tested under identical
conditions to insure the results can be compared with confidence.
The EPA GAS MILEAGE GUIDE also points outthat styfuel economyestimate simulates a 7.5 mile, stop-and-go trip with
an average speed of 20 mph. The trip takes 23 minutes and has 18 stops. About 18 percent of the time is spent idling,
as in waiting at traffic lights or in rush hour traffic. Two kinds of engine starts are used - the cold start, which is similar to
starting a car in the morning after it has been parked all night - and the hot start, similarto restarting a vehicle after it has
been warmed up, driven and stopped for a hort time.
The test to determine the highway fuel economy estimate represents a mixture of "non-city" driving. Segments
corresponding to different kinds of rural roads and interstate highways are included. The test simulates a 10 miletrip and
averages 48 mph. The test is run from a hot start and has little idling time and no stops.
The EPA GAS MILEAGE GUIDE explainsthat the actualtestresultsare aclusted downwardtoarrive attheestimates used
in the booklet and on the labels. City estimates are lowered by 10 percent and the highway estimate by 22 percent from
the laboratory test results. The guide also points out that traveling at higher speeds lowers fuel economy and traveling
at 65 mph instead of 55 mph lowers fuel economy over 15 percent.
Numerically lower axle ratios generally produce better highway fuel economy. The exception to this is if the engine is
"working" exceptionally hard, (heavy vehicle loads pulling a trailer, small engine in a large vehicle ...). In these cases
a numerically higher axle may provide betterfuel economy. Numerically higher axle ratios will also tend to provide more
fuel economy in congested city traffic and stop and go conditions.
Chevroletbulletinsare Intended foruse by professional technicians, NOTa 'dodtvourselfer.' they arewrittento Inform thesetechniciansof conditions that ffx:n
occur onsornevehicles, or to provide Information that could assist In theproper service of a vehicle. Property trainedtechnicianshavethe equipment, tools
safety Instructions, and know-howto doajobproperlyand safely. Ife condition is described, DO NOTassumethat thebtAotln appRes to your veMcie, or tho
your vehicle will have that condition. See your Chevrolet dealer for Information on whetheryour vehiclemay bonetlt from that Information.
Rev. 01 /9:
Driving Habits
Fuels
Green Engjne
Parasitic Loads
Road Conditions
Brake drag (even a minimal amount undetectable by coasting), can have a significant negative impact on fuel
economy. Pull upward on the brake pedal to assure that the stoplight switch and cruise switch at the brake pedal are
full and properly adjusted. A "lick" sound when'the pedal is pulled upward indicates that the switch was improperly
adjusted . This causes the front brake pads to lightly rub the rotors, causing a fuel economy loss, without generating
excessive heat or brake pad wear.
Frequent short trips (less than 5 miles), especially in cooler ambient temperatures (less than 65 degrees), will
necessitate fuel enrichment on start-ups, especially after "soaks* with the engine off for approximately a half hour or
more.
Frequent accelerator pedal movement while driving will reduce fuel economy because of fuel enrichment during the
periods of acceleration. Undersuchdriving conditions thetorqueconverter clutch (TCC) alsodisengages, contributing
to fuel economy losses. Prolonged idle periods reduce fuel economy especially in cold amblents when vehicle is
allowed to "warm up".
Oxygenated fuels, with methanol and/or ethanol blended into the gasoline have lower energy and thus reduce fuel
economy. Typically there is about a 1 MPG penalty for a vehicle which gets 25 to 30 MPG on 100 percent gasoline.
Usingfuelsofalower octane thanthe vehidewascalibratedtowillcause increased"KS"Knock Sensorsystem activity.
This will result in a net decrease in spark advance and thus poorer fuel economy. Using fuel of a higher octane than
the vehicle was calibrated for WILL NOT increase fuel economy.
Variations in howmuchfuel is added tothefuel tankduring re-fueling can greatly affectcalculatedfueleconomy. These
effects decrease as the distance traveled and the number of tank fillups increase .
New vehicles have not yet had an opportunity for the engine to break in, (rings toseat...). A typical engine will take
3 to 5 thousand miles to break in and during this time period a gradual increase in fuel economy can be expected.
Air conditioning and/or electrical loads, (headlights, heated badkglass . ..) also result in lower fuel economy, (typically
less than 1 MPG difference, each 10 AMPs takes approximately .4 MPG).
Road surface condition impacts fuel economy. Gravel and/or pot holed roads decrease fuel economy. Hills (vs. level
terrain) also negatively impact fuel economy. Even gradual unperceptible increases in elevation result in real
measurable decreases in fuel economy. Similarly, driving in the rain or snow decreases fuel economy.
Vehicle suspension misalignment can cause poor fuel economy. Check all four tires for abnormal and/or premature
tire wear.
New tires, tire rotation, and/or front end alignment may be required to correct fuel economy.
.L1L¢IZ
Performance tires and/or tires with larger "contact areas," (like 60 series aspect ratio), can cause as much as 3 MPG
lower fuel economy when compared to hard "thin" tires. Find out if the tire size currently on the car is the same as
original equipment. Replacement tirestaller than original equipment tires cause the odometer to read LESS THAN
actual distance traveled. This will result in lower calculated fuel economy than actual fuel economy.
Tire Pressure
Harder tires, (more air pressure, or different tire compositions) result in better fuel economy. Do not exceed
maximum pressure as labeled on the tire, typically 30-35 psi. The disadvantage of this is that the greater the tire
pressure, the harsher the vehicle ride.
Transmission
-3
On 4-Speed automatics, it is possible to drive the vehicle in 3rd gear rather than "overdrive" and not perceive it.
Typically this condition occurs when the shift indicator, or the shift linkage/detent is misadjusted. Misaclusted shift
linkage can also result in improper signals to the ECM, which can result in less spark advance, and results in a drop
in fuel economy.
Driving a vehicle in 3rd gear rather than overdrive at highway speeds typically results in a 3 to 5 MPG penalty .
Torque Converter Clutch operation isessential forgoodfuel economy. A non-locking torqueconverter typically results
in a 1 to 2 MPG penalty at highway speeds.
Vehicle Weight
Each 125 lbs . of additional weight results in a .3 MPG loss of fuel economy. Thus, additional passengers, luggage
... will decrease fuel economy.
Vehicle Wind Resistance
More wind "DRAG" means less fuel economy. Thus, hang-on luggage carriers, cat toppers, open windows and/or
open trunk... mean less fuel economy. (See "Driving Habits").
4Z~7 CHEVROLET
CHEVROLETMOTOR DIVISION Gas General Motors Corporation
Technical Service Department
subiect: OIL PRESSURE GAUGE READS HIGH
Ntodel and Year : 1991-92 P TRUCKS (MODEL 32 AND 42)
WITH 4.31_(1_134), 5.71. (1_05), 7.41_ (1_19)
Some 1991-1992 P30 (32 and 42) with gasoline engines may show high oil pressure on the dash gauge.
This condition is present only on the upper range of the oil pressure gauge (oil pressure will reflect correct
readings in the lower and midrange on the scale of the gauge) .
This high oil pressure reading may be caused by an incorrect oil pressure sending unit. Some vehicles were
built with a 60 lb. sending unit instead of the correct 80 lb. sending unit.
To correct, it will be necessary to inspect the oil pressure sending unit to determine if it is the incorrect
sending unit. This can be confirmed by the stamping on the sending unit. The incorrect sending unit (P/N
10068563) is stamped 563. The CORRECT sending unit (P/N 10096178) is stamped 178 .
SERVICE PROCEDURE:
Tools Required : J35749 Oil Pressure Sensor Socket or equivalent.
Inspection
1 . Inspect the side of the sending unit for the stamping number.
3.
4.
5.
6 .
Note : using a mirror to locate the stamping number may ease the
inspection process.
2. If the sending unit is stamped 563, it should be replaced with the
correct sending unit (P/N 10096178) using the procedure below.
Replacement of the Sending Unit
1 . Disconnect the negative battery cable.
Dealer
Service
Bulletin
2. Remove the wiring harness connector from the oil pressure sending unit.
5.71_ and 4.31_ engines-the oil pressure sending unit is located at the left front side of the distributor.
' 7.41- engines-the oil sending unit is located at the front left side of the block.
Remove the oil pressure sending unit using tool J35749 or equivalent .
Install the oil pressure sending unit (P/N 10096178) using tool J35749 or equivalent .
Connect the wiring harness connector to the oil pressure sending unit.
Connect the negative battery cable.
Number:
92-46-6A
6A
Section:
NOV. 1991
Date:
168302
Corporate Bulletin No .:
A1, A8
ASE No.:
Chevrolet bulletins are intended for use by professional technicians, NOTa -do-it-vourselfer .' They are written to inform these technicians of conditions that
may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment,
tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your
vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information.
GSD 1480 Rev. 12J89
SERVICE BULLETINS
AND
GENERAL INFORMATION
90-391-5 - Automatic Park
90-435-5 - Automatic Park
90-397-3 - Automatic Park
90-419-5 - Automatic Park
91-240-5 - Automatic Park
92-02-6E - Service Engine Light
91-151A-5 - Brake Squeak
91-133-5 - Brake Disc Rotor Refinish
91-210-7A - 4L80E Transmission
90-421-6E - Detonation - Exhaust Odor
90-368-8C - Inoperative Speedometer
92-03-6B - New Hose Clamps
91-137-9 - Cruise Control
92-12-7A - 4L80E Pan Gasket
93-57-6A - Incorrect Oil Pressure Readings
91-234A-OB - New Design Spark Plugs
88-283-6E - Electostatic Discharge Damage
93-96-6C - Factors Effecting Fuel Economy
92-46-6A - Oil Pressure Gauge Reads High
OPERATING TEMPERATURES
Engine Oil - Page 7-8 Normal engine oil temperature in between
coolant temperature and 50 degrees above.
Coolant Temperature - Oil pressure 30 to 40 PSI while driving under operating
temperature and moderate road speed .
Engine Coolant - Minimal operating temperature 2000 . Redline is 240° with
195° thermostat.
Transmission Oil - Page 8-9 .

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