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Automotix DIY provides automotive consumers and do it yourselfers; the most comprehensive repair information about 1990 GMC R3500 Pickup car and truck
repair procedures including GMC engine diagrams, wiring diagrams, repair work estimating measures, technical service bulletins, auto body work
guidance, starter & alternator replacement procedures, serpentine belt replacement procedures, radiator & hose replacement procedures, tune-up &
drivability specifications, quick lube illustrations, preventive maintenance guide, engine light reset instructions, parts removal and install
procedures, fuel filter replacement directions, component location diagrams, air filter locations & replacement instructions, a/c
system specifications, and general auto service procedures. You don't have to be a car mechanic or technician to know how to fix
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We have info for following modifications of 1990 GMC R3500 Pickup
- 1990 GMC R3500 Pickup 6.2 V8 DIESEL, CID:379, Fuel Injection, Aspiration:379, Engine VIN:, Desg:J
- 1990 GMC R3500 Pickup 5.7 V8 GAS, CID:350, Fuel Injection, Aspiration:350, Engine VIN:, Desg:K
- 1990 GMC R3500 Pickup 7.4 V8 GAS, CID:454, Fuel Injection, Aspiration:454, Engine VIN:, Desg:N
BRAKE SERVICE PROCEDURES FOR 1990 GMC R3500 Pickup AUTOMOBILES
Includes anti-lock brakes, disc, drum, power and hydraulic brake services diagnostics and procedures for domestic and imported 1990 GMC R3500 Pickup cars and light trucks from 1990+.
POWER BRAKE UNITS, GENERAL MOTORS -> Delco-Moraine Brake Boosters -> TANDEM DIAPHRAGM TYPE -> Assemble -> BOOSTER SERVICE -> DESCRIPTION -> Disassemble
Vehicle: 1990 GMC R3500 Pickup 6.2 V8 DIESEL
DESCRIPTION
These units, Figs. and , have a vacuum power chamber that consists of a front and rear shell, a housing divider, front and rear diaphragm and plate assemblies, an hydraulic pushrod and a diaphragm return spring.
The unit operates in much the same manner as the Single Diaphragm unit described above. The diaphragm and plate assemblies use the pressure differential created by engine intake manifold vacuum and atmospheric pressure to assist the hydraulic pushrod.
BOOSTER SERVICE
Disassemble
- Remove boot, silencer, vacuum check valve, grommet and front housing seal Fig. ...
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BRAKE SERVICE PROCEDURES FOR 1990 GMC R3500 Pickup AUTOMOBILES
Includes anti-lock brakes, disc, drum, power and hydraulic brake services diagnostics and procedures for domestic and imported 1990 GMC R3500 Pickup cars and light trucks from 1990+.
POWER BRAKE UNITS, GENERAL MOTORS -> General Service -> CHECKING COMPLAINTS
Vehicle: 1990 GMC R3500 Pickup 6.2 V8 DIESEL
Diagnose power brakes systems as if two separate systems exist. Check for faults in the regular brake system first. If no problem exists in the regular brake system, diagnosis the power brake circuit is necessary. For a quick check of proper power unit operation, press the brake pedal firmly and then start the engine. The pedal should fall away slightly and less pressure should be needed to maintain the pedal in any position. On vacuum suspended power units, air will rush into the air intake when the brakes are applied.
To perform another check, remove the stop light switch, ...
CLICK HERE TO GET FULL ACCESS TO 1990 GMC R3500 Pickup BRAKE SERVICE PROCEDURES
BRAKE SERVICE PROCEDURES FOR 1990 GMC R3500 Pickup AUTOMOBILES
Includes anti-lock brakes, disc, drum, power and hydraulic brake services diagnostics and procedures for domestic and imported 1990 GMC R3500 Pickup cars and light trucks from 1990+.
ANTI-LOCK BRAKES, GENERAL MOTORS -> Rear Wheel Anti-Lock Brake System -> DIAGNOSIS & TESTING -> DIAGNOSTIC CHARTS -> DIAGNOSTIC CIRCUIT CHECK -> READING TROUBLE CODES -> WIRING DIAGRAMS
Vehicle: 1990 GMC R3500 Pickup 7.4 V8 GAS
WIRING DIAGRAMS
Refer to "Wiring Diagrams" in "Vehicle Systems."
READING TROUBLE CODES
Trouble codes are accessed by connecting a jumper wire between terminals A and H of the underdash ALDL connector and observing the flashes of the brake warning lamp. Note the following when performing the Diagnostic Circuit Check to access trouble codes.
- When the terminals are jumped, count the number of short flashes starting from the initial long flash and including the long flash in the count.
- The count sequence will repeat as long as the ALDL connector terminals are jumped with the ignition on.
- ...
CLICK HERE TO GET FULL ACCESS TO 1990 GMC R3500 Pickup BRAKE SERVICE PROCEDURES
BRAKE SERVICE PROCEDURES FOR 1990 GMC R3500 Pickup AUTOMOBILES
Includes anti-lock brakes, disc, drum, power and hydraulic brake services diagnostics and procedures for domestic and imported 1990 GMC R3500 Pickup cars and light trucks from 1990+.
ANTI-LOCK BRAKES, GENERAL MOTORS -> Rear Wheel Anti-Lock Brake System -> DESCRIPTION
Vehicle: 1990 GMC R3500 Pickup 7.4 V8 GAS
The Rear Wheel Anti-Lock (RWAL) system, Fig. , reduces the occurrence of rear wheel lockup during severe braking by regulating rear hydraulic line pressure. Pressure applied to the rear wheel brakes is regulated by a control valve assembly located under the master cylinder. The control valve consists of a dump valve which releases hydraulic pressure into an accumulator, and an isolation valve which holds rear brake pressure. Operation of the dump valve and isolation valve is controlled by an Electronic Control Unit (ECU) which is mounted next to the master cylinder.
The ECU receives ...
CLICK HERE TO GET FULL ACCESS TO 1990 GMC R3500 Pickup BRAKE SERVICE PROCEDURES
BRAKE SERVICE PROCEDURES FOR 1990 GMC R3500 Pickup AUTOMOBILES
Includes anti-lock brakes, disc, drum, power and hydraulic brake services diagnostics and procedures for domestic and imported 1990 GMC R3500 Pickup cars and light trucks from 1990+.
POWER BRAKE UNITS, GENERAL MOTORS -> Delco-Moraine Brake Boosters -> TROUBLESHOOTING -> BRAKES GRAB -> HARD PEDAL -> SLOW OR NO RELEASE
Vehicle: 1990 GMC R3500 Pickup 5.7 V8 GAS
HARD PEDAL
- Internal vacuum leak.
- Faulty control valve.
- Broken or damaged hydraulic brake lines.
- Collapsed or damaged vacuum hose.
- Plugged or loose vacuum fitting.
- Bad stud welds on front or rear housing on power head.
- Faulty booster diaphragm.
- Restricted air filter element.
- Worn or distorted reaction plate or levers.
- Cracked or broken pow...
CLICK HERE TO GET FULL ACCESS TO 1990 GMC R3500 Pickup BRAKE SERVICE PROCEDURES
BRAKE SERVICE PROCEDURES FOR 1990 GMC R3500 Pickup AUTOMOBILES
Includes anti-lock brakes, disc, drum, power and hydraulic brake services diagnostics and procedures for domestic and imported 1990 GMC R3500 Pickup cars and light trucks from 1990+.
POWER BRAKE UNITS, GENERAL MOTORS -> Bendix Brake Boosters -> HYDRO-BOOST II -> BLEEDING BOOSTER -> CLEANING & INSPECTION -> DESCRIPTION -> DISASSEMBLE & ASSEMBLE
Vehicle: 1990 GMC R3500 Pickup 7.4 V8 GAS
DESCRIPTION
Hydro-Boost II is an hydraulically operated power brake booster. The hydraulic brake booster consists of an open center spool valve and an hydraulic cylinder combined into a single housing. The power steering pump provides the hydraulic fluid pressure to operate both the power brake booster and the power steering gear.
A dual master cylinder is bolted to the brake booster and is operated by a pushrod projecting from the booster cylinder bore.
The Hydro-Boost II also has an accumulator system which stores sufficient fluid under pressure to provide one power assisted brake...
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