2001 GMC Safari Brake Service (ONLINE REPAIR MANUALS)

Excessive Pedal Travel

• Worn brake linings.
• Disc pads knock back after cornering or rough road travel.
• Piston and linings not properly seated or positioned.
• Insufficient fluid in system.
• Loose wheel bearing adjustment.
• Damaged or worn caliper piston seal.
• Improper booster pushrod adjustment.
• Pads out of flat more than .005 inch.
• Rear brake automatic adjusters inoperative.
• Improperly ground rear brake shoes.

Brake Roughness Or Chatter; Pedal Pumping

• Excessive lateral runout of rotor.
• Rotor excessively out of parallel.

Excessive Pedal Effort

• Frozen or seized pistons.
• Brake fluid, oil or grease on ...

Hard Pedal

• Internal vacuum leak.
• Faulty control valve.
• Broken or damaged hydraulic brake lines.
• Collapsed or damaged vacuum hose.
• Plugged or loose vacuum fitting.
• Bad stud welds on front or rear housing on power head.
• Faulty booster diaphragm.
• Restricted air filter element.
• Worn or distorted reaction plate or levers.
• Cracked or broken pow...

This system is used on all models except Montana, Silhouette, Tracker, Trans Sport and Venture. On 2000 S & T Series , four door utility vehicles can be equipped with either a 310 or 325 ABS system. Pickups and two-door utility vehicles are equipped with 310 ABS systems. While both systems are functionally the same, the 310 differs in size and appearance from the 325. It 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 (EHC...

Removal

Front

• Siphon brake fluid out of master cylinder until fluid level is approximately ^1/3 full, this will prevent fluid overflow when caliper piston is pushed back into its bore.
• Raise and support vehicle, then remove wheels.
• Push piston back into its bore using suitable C-clamp, Fig. .
• Remove two caliper mounting bolts and lift caliper off of rotor.

Rear

Blazer, Bravada & Jimmy

• Raise and support vehicle.
• Mark position of wheel to hub for installation reference.
• Remove wheel assembly.
• Remove mounting bolt and disconnect brake hose fitting from caliper. Discard gaskets and plug brake h...

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, on models with hydraulic assist brakes, 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 brak...

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...