2002 GMC Savana 3500 Brake Service (ONLINE REPAIR MANUALS)

In order to properly service power brake systems, a thorough understanding of the power assist system is required. These systems provide a mechanical assist, acting to increase the force applied to the master cylinder piston by the driver while decreasing the effort required 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 fluid ...

Delco Master Cylinder

When performing the following procedures, refer to. Figs. and , noting that the composite reservoir may vary in design.

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.
• Plug primary fluid outlet (outlet nearest to cowl when master cylinder is installed), then apply compressed air into secondary fluid outlet...

C & K Series

Duo-Servo

Removal

• Raise and support vehicle.
• Mark relationship of wheel to hub, then remove tire and wheel assembly.
• On models equipped with full-floating axles, remove hub and drum assembly as outlined in. "Drive Axles."
• On models equipped with semi-floating axles, proceed as follows:
• Install pin into park brake lever.
• Mark relationship of drum to axle.
• Remove rear brake drum retainers, as required.
• Remove rear brake drum.
• On all models, remove return springs and shoe guide,. Fig. .
• Remove brake hold down springs and pins.
• Disconnect actuator lever and pivot.
• Remove lever return sp...

Delco Master Cylinder

When performing the following procedures, refer to. Figs. and , noting that the composite reservoir may vary in design.

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.
• Plug primary fluid outlet (outlet nearest to cowl when master cylinder is installed), then apply compressed air into secondary fluid outlet...

General System

• Inspect components for damage or unusual wear. Replace as required.
• Inspect backing plate mounting bolts and ensure they are tight.
• Inspect wheel cylinders. Excessive fluid indicates cup leakage and need for wheel cylinder replacement. Slight amount of fluid is always present and is considered normal, acting as lubricant for cylinder pistons.
• Inspect adjuster screw operation. If satisfactory, lightly lubricate adjusting screw and washer with suitable brake lube. If operation is unsatisfactory, replace.
• Clean rust and dirt from shoe contact surfaces on backing plate using fi...

When working on or around brake assemblies, care must be taken to prevent breathing asbestos dust, as many manufacturers incorporate asbestos fibers in the production of brake linings. During routine service operations, the amount of asbestos dust from brake lining wear is at a low level because of a chemical breakdown during use and a few precautions will minimize exposure.. Do not sand or grind brake linings unless suitable local exhaust ventilation equipment is used to prevent excessiv...