1995 GMC K2500 Suburban Brake Service (ONLINE REPAIR MANUALS)

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...

Astro & Safari

• 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.
• Reverse procedure to install.

Full Size Except C & K Series

• Remove master cylinder attaching nuts and position master cylinder aside. Do not disconnect brake lines from cylinder.
• Disconnect power brake unit pushrod from brake pedal.
• Remove attaching nuts, then the power brake unit.
• Reverse procedure to install.

S/T Series & Bravada

• Disconnect master cylinder assembly and vacuum hose from power br...

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...

In order to properly service power brake systems, a thorough understanding of the power assist system 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.

Hydraulic assist units incorporate a basic open center spool valve, hydraulic cylinder and an accumulator assembly in a common housing. When the brake pedal is depressed, the hydraulic piston moves forward closing off fluid relief passages, the spool valve applies flui...

The braking system can be bled manually or with pressure bleeding equipment. If bleeding manually, check fluid level frequently.

Brake fluid should never be reused. Before driving the vehicle, check brake operation to ensure a firm pedal has been obtained.

Brake fluid will damage electrical connections and painted surfaces. Use shop cloths, suitable containers, and fender covers to prevent brake fluid from contacting these areas. Always seal and wipe off brake fluid containers to prevent spills.

Manual Bleeding

C/K, G, M/L, P & S/T Series

• If vehicle is equipped with a vacuum or hy...

Certain general service procedures apply, regardless of whether the brakes are vacuum or hydraulically assisted. Only top quality, clean brake fluid should be used. More seals and valves are used with power brake systems than with ordinary brakes, so an inferior brake fluid will do much more damage. For the same reason, be sure all dirt is kept out of the system. Additionally, care must be taken not to mix the fluids of the booster hydraulic system and brake hydraulic system as the fluids are not compatible.

If the power unit fails, the brakes will still operate, as the conventio...