Four-Piston Fixed Caliper
See Figure 1
- Remove and discard approximately 2 / 3 of the brake fluid from the rear master cylinder reservoir.
- Raise the vehicle on a hoist and remove the front wheels. Remove the dust shield or antirattle clips and shoe and lining assemblies.
- Working on one side at a time, disconnect the flexible brake hose from the brake tube at the bracket on the frame. Plug the end to prevent loss of fluid.
- Remove the two caliper retaining bolts and slide the caliper off the disc. Place the caliper assembly in a padded jaw vise, clamping on the caliper mounting lugs.
- Remove the hydraulic crossover line and bleeder screw.
- Remove the bridge bolts holding the caliper halves together and separate the assemblies.
- Remove each of the four dust boots. Raise the inner diameter of the boot out of the piston groove and slide it back on the piston. Remove the outer diameter of the boot from the cylinder groove after the piston has been removed.
- Remove the pistons being careful not to burr, scratch, or otherwise damage the outside diameter or boot groove of the piston.
- Using a small, pointed, plastic implement, remove the piston seals from the grooves in the cylinder bores. Be careful not to scratch the cylinder bores.
- Discard all old rubber boots and seals. Clean all parts with brake fluid and wipe them dry with a clean, lint-free cloth. Blow out the drilled passages and bores with an air hose.
- Check the cylinder bores in both caliper housing castings for scoring or pitting. Light scratches or corrosion in the bores may be removed only with crocus cloth. Avoid using extreme pressure with the cloth. Check the dust boot retaining rings on the caliper housing for damage.
Black stains in the bore are caused by the rubber piston seals and are considered normal.
- Inspect each piston and replace if it is scored, pitted, or if the chrome plating is wearing off.
- Dip the new piston seals in fresh, clean brake fluid and install them in the cylinder grooves. Position the seal at one area in the groove and gently work around the cylinder bore with a finger until properly seated. Be careful not to twist or roll the seals. If it is necessary to replace the dust boot retaining rings, thoroughly clean the contact area on the housing, and apply Loctite Sealant Grade H or its equivalent to the retaining rings and the seating surfaces, and install the retaining rings.
- Coat the outside diameter of the pistons with brake fluid and install them, hollow end out, in the bores.
- Position the piston squarely within the bore and apply slow, steady pressure until the piston bottoms within its bore. Use no tools to accomplish this seating. If the piston fails to move freely, remove it and check to make sure that the seal is properly seated. Install the new dust boots in position over the caliper retaining rings and in the piston grooves. Make certain that the dust boots are properly seated.
- Upon installation of all four pistons, with seals and boots, into their respective caliper castings, install the outer caliper casting and bridge bolts. Tighten to 75-105 ft. lbs.
Bridge bolts are special high tensile steel. Use only factory replacement bolts, if replacement is necessary.
- Install the hydraulic crossover line and tighten securely. Install the bleeder screw finger-tight.
- Prior to installing the caliper assembly over the rotor, hand-spin the rotor, and visually check for wobbling or lateral run-out. Make sure that the wheel bearing is adjusted to zero end-play during this check. Readjust the wheel bearing as outlined in the Wheel Bearing Adjustment procedure.
- Place the caliper assembly over the rotor and install the mounting bolts. Tighten to 45-60 ft. lbs. Check to make sure that the rotor runs squarely and centerally between the two halves of the caliper. There should be approximately 0.090-0.120 inch clearance between the outside diameter of the braking rotor and the caliper. There should be a minimum of 0.050 inch from either rotor face to the machined groove in the outboard caliper.
- Install the shoe and lining assemblies on each side between the caliper and the braking rotor.
- Position the caliper splash shield or antirattle clips on the caliper and install the attaching bolts. Make sure that the splash shield opening is centered over the rotor. Torque the bolts to 9-14 ft. lbs.
- Open the bleed screw and completely bleed the system. Allow the caliper to fill with brake fluid. After all air bubbles have escaped, close the bleeder screw. Top up the master cylinder.
- Depress the brake pedal several times to actuate the piston seals and seat the shoe and lining assemblies.
- Check all hydraulic connections for leaks.
- Install the wheel and tire assembly and torque the nuts to 75-110 ft. lbs. Install the wheel cover.
- Lower and road-test the vehicle.
See Figure 2
- Raise the vehicle on a hoist and remove the front wheels.
- Disconnect and plug the brake line.
- Remove the lockwires from the two caliper mounting bolts and remove the bolt. Lift the caliper off the disc.
- Remove and discard the locating pin insulators. Replace all rubber parts at reassembly.
- Remove the retaining clips with a screwdriver and slide the outboard pad and retaining pins out of the caliper. Remove the inboard pad. Loosen the bleed screw and drain the brake fluid.
- Remove the two small bolts and caliper stabilizers.
- Remove the inboard pad retaining clips and bolts.
- Clean and inspect all parts, and reinstall them on the anchor plate. Do not tighten the stabilizer bolts at this time.
- Remove the piston by applying compressed air to the fluid inlet hole. Use care to prevent the piston from popping out of control.
- Remove the piston boot. Inspect the piston for scoring, pitting, or corrosion. The piston must be replaced if there is any visible damage or wear.
- Remove the piston seal from the cylinder bore. [cf2]Do not use any metal tools for this operation.
- Clean the caliper with fresh brake fluid. Inspect the cylinder bore for damage or wear. Light defects can be removed by rotating crocus cloth around the bore. (Do not use any other type of abrasive.)
- Lubricate all new rubber parts in brake fluid. Install the piston seal in the cylinder groove. Install the boot into its piston groove.
- Install the piston, open end out, into the bore while working the boot around the outside of the piston. Make sure the boot lip is seated in the piston groove.
- Slide the anchor plate assembly onto the caliper housing and reinstall the locating pins. Tighten the pins to specification. Tighten the stabilizer anchor plate bolts.
- Slide the inboard pad into the caliper so that the tabs are between the retaining clips and anchor plate and the backing plate lies flush against the piston.
- Insert the outboard pad retaining pins into the outboard pad and position them in the caliper.
- Hold the retaining pins in place (one at a time) with a short drift pin or dowel and install the retaining clips.
- Slide the caliper assembly over the disc and align the mounting bolt holes.
- Install the lower bolt finger-tight. Install the upper bolt and tighten to specification. Torque the lower bolt to specification. Safety-wire both bolts.
- Connect the brake line and bleed the brakes (see Brake Bleeding).
- Install the front wheels, recheck the brake fluid level, and road-test the car.