Removal & Installation
Several types of front brake calipers have been used on GM W-Body vehicles. The primary difference is some vehicles use a double-piston front caliper, while others use a single piston. Use care when ordering replacement parts. The caliper is mounted to the support bracket with two mounting bolts.
- Using a clean suction gun, remove approximately 2 / 3 of the brake fluid from the master cylinder. The reason for this is that the caliper pistons must be pushed back into their bores so the caliper can be removed from the rotor. This could cause the brake fluid to overflow from the reservoir onto painted surfaces or wiring.
- Raise and safely support the vehicle on safety stands.
- Mark the relationship of the wheel to the hub so it can later be installed in the same relationship. This helps retain the balance of the rotating assembly.
- Remove the front tire and wheel assembly. Install two wheel lug nuts to keep the rotor on the hub. Remove the caliper slide pin bolts and carefully work the caliper away from the rotor and caliper mounting bracket.
- Push the caliper piston(s) back into their bore(s) to provide clearance between the linings and rotor. Use a large C-clamp over the top of the caliper housing and against the back of the outboard pad. Slowly tighten the C-clamp until the piston(s) are pushed back into the caliper bore(s) enough to slide the caliper off the rotor.
- Remove the outboard brake pad. Use a small prytool to lift up on the outboard pad retaining spring so it will clear the caliper center lug.
- Remove the inboard brake pad, unsnapping the pad springs from the inside of the piston bores.
- The caliper mounting bolts (also called slide pins) are important because, in use, the caliper moves (slides) a small amount, along the bolts. This "floating" action is key to the caliper's ability to self-adjust. The bolts must be clean of rust and corrosion. Small rubber boots on the mounting bolts are designed to keep out water and road debris. Inspect the pin boots for cuts, tears or deterioration. If corrosion is found, use new replacement parts including bushings when installing the caliper. GM does not recommend attempting to polish away corrosion. Any protective coating still on the mounting bolts would then be abraded away and corrosion will return in an even shorter time. As insurance against brake problems, many professionals routinely replace the caliper mounting bolts (often sold as "pin kits") during disc brake pad replacements.
- Inspect the caliper for signs of leaks. While seal kits may be available for caliper overhaul, most professional technicians will simply install a new or factory rebuilt caliper, when required.
- Bottom the piston(s) in the caliper bore(s) using a C-clamp, if new brake pads are to be installed. Use a large C-clamp and a metal plate or wooden block across the face of the piston(s). Take care not to damage the piston(s) or caliper rubber dust boot(s). After bottoming the piston(s), carefully lift the inner edge of the caliper boot(s) next to the piston(s) and press out any trapped air. The boots must lay flat below the level of the piston face.
- Install the inboard brake pad by snapping the pad retainer springs into the hollow of the pistons. Make sure both tangs of the retainer springs are installed inside the hollows (openings) of the pistons. After installing the brake pads, check that the caliper boots are not touching the pads. If there is any contact, remove the brake pads and reseat or reposition the boots.
- Install the outboard brake pads by snapping the outboard pad retaining springs over the caliper center lug and into the housing slot. The brake pad wear sensor should be at the trailing edge of the brake pad during forward wheel rotation. The back of the pad must lay flat against the caliper.
- Install the caliper over the rotor and mounting bracket and work into place. Make sure the bushings in the caliper bracket are still in place.
- Carefully lubricate the caliper mounting bolts (slide pins) using silicone grease. Do not lubricate the threads or the mounting bolts may tend to work loose. Lubricate the two rubber bushings in the caliper mounting bracket using silicone grease. Install the caliper mounting bolts. Use a small flat-blade tool to push the pin boot over the shoulder of the mounting bolt. The pin boot must be securely in the groove of the mounting bolt. Torque the caliper mounting bolts to 80 ft. lbs. (108 Nm).
- Install the tire and wheel assembly, aligning the balance marks made at removal.
- Lower the vehicle.
- Fill the master cylinder reservoir to the proper level using only fresh, clean DOT 3 brake fluid. Pump the brake pedal firmly to push the pistons back out into operating position and to seat the lining.
After the brake pads have been replaced and/or rotors have been refinished, GM recommends that new brake pads be broken in, or "burnished". Use the following procedure:
- Make 20 stops from 30 mph using medium to firm brake pedal pressure.
- Take care to avoid overheating the brakes.