1994 GMC K1500 Pickup Brake Service (ONLINE REPAIR MANUALS)

• Inspect components for damage or unusual wear. Replace as necessary.
• Inspect backing plate attaching bolts, and ensure they are tight.
• Inspect wheel cylinders. Excessive fluid indicates cup leakage and need for wheel cylinder replacement. A slight amount of fluid is always present and is considered normal, act...

Accessing Diagnostic Trouble Codes

This system has a sophisticated diagnosis system designed to identify any system fault as specifically as possible, including intermittent faults. There are many diagnostic trouble codes used by the system. Each input and output to the system can be monitored with a suitable bi-directional scan tool; monitoring inputs and outputs allows for fault confirmation and repair verification. The scan tool can also be used to manually control components and perform functional tests.

• Connect a TECH 1 or equivalent scan tool to the diagnostic connector,...

1992

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 rec...

Brake Lines & Linings

Remove one of the front wheels and inspect the brake disc, caliper and linings.

Do not allow any oil or grease on the linings. It is recommended that all linings be replaced in sets when worn or damaged.

If the caliper is cracked or fluid leakage through the casting is evident, it must be replaced as a unit.

Brake Roughness

The most common cause of brake chatter on disc brakes is a variation in thickness of the disc. If roughness or vibration is encountered during highway operation or if pedal pumping is experienced at low speeds, the disc may have excessive thickne...

Delco-Moraine Master Cylinder

Composite Type

When performing the following procedures, refer to Fig. for all models except Lumina APV, Silhouette & Trans Sport, noting that the composite reservoir may vary in design. Refer to Fig. for Lumina APV, Silhouette & Trans Sport models.

Disassemble

• Remove master cylinder from vehicle.
• Remove reservoir cover and diaphragm. Discard old brake fluid in reservoir.
• Inspect cover and diaphragm. Replace if cut, cracked or deformed.
• Remove fluid level switch and proportioning valve assembly, if equipped.
• Depress primary piston and remove lock ring.
• P...

Single Diaphragm Type

Disassemble

• Remove boot, silencer, vacuum check valve, grommet and front housing seal, Fig. .
• Scribe a line across front and rear housing, then mount brake booster to brake mounting fixture tool No. J 23456 or equivalent, Fig. .
• Turn fixture handle counterclockwise to unlock housings.
• Remove return spring, power piston assembly and power piston bearing from rear housing, Fig. .
• Remove reaction body retainer, piston rod, reaction retainer and filter.
• Remove power piston and pushrod assembly as follows:
• While holding the pushrod down against a hard surface, ...