1996 GMC P35/P3500 VAN Brake Service (ONLINE REPAIR MANUALS)

Removal

• Siphon enough brake fluid out of the master cylinder to bring fluid level to ^1/3 full to avoid fluid overflow when the caliper piston is pushed back into its bore.
• Raise and support vehicle, remove front wheels.
• Using a C-clamp, Fig. , push piston back into its bore.
• Remove two mounting bolts and lift caliper away from disc.

Inspection

Should it become necessary to remove the caliper for installation of new parts, clean all parts in denatured alcohol, wipe dry using lint-free cloths. Using compressed air, blow out drilled passages and holes. Check dust boots for punctures or t...

Except S & T Series w/VCM & VCM-A

This braking system, Figs. through , 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 Electro-Hydraulic Control Unit (EHCU) module or a Brake Pressure Modulator Valve (BPMV). The EHCU/BPMV module has two types of valves: isolation valves, which maintain separate pressure for each front wheel and combine pressure for the rear wheels, and dump valves, which "dump" pressure to each front wheel separately and rear wheels comb...

Master Cylinder

Some vehicles use a conventional tandem master cylinder with two hydraulic pistons operating inline. The primary piston controls the front brake system and the secondary piston controls the rear brake system.

Other models use a master cylinder that operates the same as the conventional master cylinder, but also incorporates a quick take-up feature in the rear chamber to reduce excessive pedal travel which may result from increased fluid displacement required to move the low drag caliper piston out against the rotor.

The quick take-up uses a spring-loaded ball check valv...

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...

4WD Models

• Raise and support vehicle.
• Remove tire and wheel.
• Remove caliper as outlined under "Caliper Service."
• On ^K1500 and ^K2500 models, remove rotor.
• On K3500 models proceed as follows:
• Remove hub retaining nut.
• Remove four hub/rotor retaining bolts on back side of spindle.
• Using suitable wheel puller, remove rotor assembly.
• On K1500 and K2500 models, reverse procedure to install, tightening all bolts to specifications. Install caliper as outlined under "Caliper Service."
• On K3500 models, reverse procedure to install, noting the following:
• Torque hub nut to 173 ft. lbs
• Torque hub and bear...

2WD Models

• Raise and support vehicle.
• Remove tire and wheel assembly.
• Remove caliper as outlined under "Caliper Service."
• Remove grease cap from hub/rotor.
• Remove cotter pin, nut and washer.
• Remove hub/rotor from spindle, being careful not to damage spindle threads or outer bearing.
• Reverse procedure to install, noting the following:
• Apply high-temperature wheel bearing grease to inner and outer wheel bearings.
• Torque nut to 12 ft. lbs. while turning wheel assembly forward by hand, back...