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Automotix DIY provides automotive consumers and do it yourselfers; the most comprehensive repair information about 1990 GMC S15 Jimmy car and truck
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BRAKE SERVICE PROCEDURES FOR 1990 GMC S15 Jimmy AUTOMOBILES
Includes anti-lock brakes, disc, drum, power and hydraulic brake services diagnostics and procedures for domestic and imported 1990 GMC S15 Jimmy cars and light trucks from 1990+.
POWER BRAKE UNITS, GENERAL MOTORS -> General Service -> DESCRIPTION
Vehicle: 1990 GMC S15 Jimmy 4.3 V6 GAS
In order to properly service power brake systems, a thorough understanding of the various power assist systems is necessary. These systems provide a mechanical assist, acting to increase the force applied to the master cylinder piston by the driver while decreasing the effort necessary to obtain acceptable stopping performance. Two basic types of power assist mechanisms are used: vacuum assist diaphragm assemblies which use engine vacuum and in some cases vacuum from an external vacuum pump, and hydraulic assist assemblies which use hydraulic pressure developed by an external pump (...
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BRAKE SERVICE PROCEDURES FOR 1990 GMC S15 Jimmy AUTOMOBILES
Includes anti-lock brakes, disc, drum, power and hydraulic brake services diagnostics and procedures for domestic and imported 1990 GMC S15 Jimmy cars and light trucks from 1990+.
POWER BRAKE UNITS, GENERAL MOTORS -> Bendix Brake Boosters -> TROUBLESHOOTING -> ACCUMULATOR LEAK-DOWN, SYSTEM DOES NOT HOLD CHARGE -> GRABBY BRAKES OR BOOSTER CHATTERS/PEDAL VIBRATES -> SLOW BRAKE PEDAL RETURN
Vehicle: 1990 GMC S15 Jimmy 4.3 V6 GAS
SLOW BRAKE PEDAL RETURN
- Excessive seal friction in booster.
- Faulty spool action.
- Restriction in return line from booster to pump reservoir.
- Damaged input rod end.
GRABBY BRAKES OR BOOSTER CHATTERS/PEDAL VIBRATES
- Faulty spool action caused by contamination in ...
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BRAKE SERVICE PROCEDURES FOR 1990 GMC S15 Jimmy AUTOMOBILES
Includes anti-lock brakes, disc, drum, power and hydraulic brake services diagnostics and procedures for domestic and imported 1990 GMC S15 Jimmy cars and light trucks from 1990+.
POWER BRAKE UNITS, GENERAL MOTORS -> Delco-Moraine Brake Boosters -> POWER BRAKE UNIT, Replace -> 1990-91 C & K SERIES -> ASTRO & SAFARI VAN -> CABALLERO & EL CAMINO -> FULL SIZE EXCEPT 1990-91 C & K SERIES -> LUMINA APV, SILHOUTTE & TRANS SPORT -> S/T 10 & 15 & BRAVADA
Vehicle: 1990 GMC S15 Jimmy 4.3 V6 GAS
CABALLERO & EL CAMINO
- Remove vacuum hose from check valve and master cylinder retaining nuts.
- Pull master cylinder forward so it clears mounting studs and move to one side. Support cylinder to avoid stress on hydraulic lines.
- Remove power unit to dash nuts.
- Remove brake pedal pushrod retainer and disconnect pushrod from pin.
- Remove power brake unit from vehicle.
- Reverse procedure to install.
ASTRO & SAFARI VAN
- Disconnect master cylinder from power brake unit.
- Disconnect power brake unit pushrod from brake pedal.
- Remove power brake unit retaining nuts and the power brake unit.
- Rev...
CLICK HERE TO GET FULL ACCESS TO 1990 GMC S15 Jimmy BRAKE SERVICE PROCEDURES
BRAKE SERVICE PROCEDURES FOR 1990 GMC S15 Jimmy AUTOMOBILES
Includes anti-lock brakes, disc, drum, power and hydraulic brake services diagnostics and procedures for domestic and imported 1990 GMC S15 Jimmy 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 S15 Jimmy 4.3 V6 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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BRAKE SERVICE PROCEDURES FOR 1990 GMC S15 Jimmy AUTOMOBILES
Includes anti-lock brakes, disc, drum, power and hydraulic brake services diagnostics and procedures for domestic and imported 1990 GMC S15 Jimmy cars and light trucks from 1990+.
DISC BRAKES, GENERAL MOTORS -> General Information -> TROUBLESHOOTING -> BRAKE RATTLE -> BRAKE ROUGHNESS OR CHATTER; PEDAL PUMPING -> CALIPER BRAKE FLUID LEAK -> EXCESSIVE PEDAL EFFORT -> EXCESSIVE PEDAL TRAVEL -> HEAVY BRAKE DRAG -> NO BRAKING EFFECT WHEN BRAKE PEDAL IS DEPRESSED -> PULL, UNEVEN OR GRABBING BRAKES -> REAR BRAKES LOCKING ON APPLICATION
Vehicle: 1990 GMC S15 Jimmy 4.3 V6 GAS
EXCESSIVE PEDAL TRAVEL
- Worn brake linings.
- Disc pads knock back after cornering or rough road travel.
- Piston and linings not properly seated or positioned.
- Insufficient fluid in system.
- Loose wheel bearing adjustment.
- Damaged or worn caliper piston seal.
- Improper booster pushrod adjustment.
- Pads out of flat more than .005 inch.
- Rear brake automatic adjusters inoperative.
- Improperly ground rear brake shoes.
BRAKE ROUGHNESS OR CHATTER; PEDAL PUMPING
- Excessive lateral runout of rotor.
- Rotor excessively out of parallel.
EXCESSIVE PEDAL EFFORT
- Frozen or seized pistons.
- Brake fluid, oil or grease on ...
CLICK HERE TO GET FULL ACCESS TO 1990 GMC S15 Jimmy BRAKE SERVICE PROCEDURES
BRAKE SERVICE PROCEDURES FOR 1990 GMC S15 Jimmy AUTOMOBILES
Includes anti-lock brakes, disc, drum, power and hydraulic brake services diagnostics and procedures for domestic and imported 1990 GMC S15 Jimmy cars and light trucks from 1990+.
ANTI-LOCK BRAKES, GENERAL MOTORS -> Four Wheel Anti-Lock Brake System -> DESCRIPTION
Vehicle: 1990 GMC S15 Jimmy 4.3 V6 GAS
This braking system Fig. is designed to reduce the occurrence of wheel lock-up during severe braking conditions. To accomplish this function, the system regulates hydraulic brake line pressure by using an Electronic Hydraulic Control Unit (EHCU) module. This control module has two types of valves. Isolation valves which maintain pressure to each front wheel separately and rear wheels combined. Dump valves which dump pressure to each front wheel separately and rear wheels combined. These valves are controlled by a microcomputer which is part of the EHCU module. During a severe brak...
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