2003 Chevrolet Express 3500 Brake Service (ONLINE REPAIR MANUALS)

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...

Master Cylinder

Some vehicles use a conventional tandem master cylinder with two hydraulic pistons operating in-line. 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 val...

Astro & Safari

• Apply parking brake.
• Disconnect reservoir and power steering hoses from booster.
• Remove master cylinder to brake booster retaining nuts.
• Position and support master cylinder away from booster.. Do not remove hydraulic lines from master cylinder.
• Remove booster rod from top of brake pedal.
• Remove booster mounting nuts from inside of vehicle.
• Remove booster assembly and gasket.
• Reverse procedure to install, noting the following:
• Torque booster mounting nuts to 27 ft. lbs.
• Torque master cylinder retaining nuts to 27 ft. lbs.
• Torque power steering hoses to booster n...

When wheel slip is detected during a brake application, the ABS enters anti-lock mode. During anti-lock braking, hydraulic pressure in the individual wheel circuits is controlled to prevent any wheel from slipping. A separate hydraulic line and specific solenoid valves are provided for each wheel. The ABS can decrease, hold, or increase hydraulic pressure to each wheel brake. The ABS cannot, however, increase hydraulic pressure above the amount which is transmitted by the master cylinder during braking.

During anti-lock braking, a series of rapid pulsations is felt in the brake pedal...

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...

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, ensure 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 convention...