GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide

Brake Caliper

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See Figure 1

REMOVAL & INSTALLATION 2 / 3 of the brake fluid from the master cylinder.



  1. Siphon off
  2.  

The insertion of the thicker replacement pads will push the caliper piston back into its bore and will cause a full master cylinder to overflow.

  1. Raise the rear of the vehicle and support it with safety stands. Remove the wheel and tire assembly.
  2.  
  3. Reinstall two lug nuts to keep the rotor from turning.
  4.  
  5. Remove the retaining clip from the parking brake actuator lever.
  6.  
  7. Disconnect the parking brake cable and spring from the lever.
  8.  
  9. While holding the parking brake lever in place, remove the lock nut. Remove the lever, lever seal and the anti-friction washer.
  10.  
  11. If the caliper is to be overhauled or replaced, remove the bolt attaching the brake line inlet fitting.
  12.  
  13. Remove the caliper mounting bolts and then remove the caliper from the rotor and mounting bracket.
  14.  
  15. Check the lever seal and the anti-friction washer for wear and replace if worn.
  16.  
  17. Check the mounting bolts for any wear or damage, replace if necessary. Check the bolt boots, support bushings and caliper piston boot for any wear, cracking or other damage, replace as necessary.
  18.  
  19. Replace the insulators.
  20.  
  21. To install, coat the entire shaft of the caliper mounting bolts with a thin film of silicone grease.
  22.  
  23. Slide the caliper over the rotor and into the mounting bracket. Make sure that the new insulators are in position. Tighten the mounting bolts to 63 ft. lbs. (85 Nm).
  24.  
  25. If you disconnected the inlet fitting, install it and tighten to 32 ft. lbs. (44 Nm). Use two NEW copper washers.
  26.  
  27. Lubricate the parking brake lever seal with silicone grease and then install it and the anti-friction washer.
  28.  
  29. Install the lever onto the actuator screw hex so that it is pointing as shown in the illustration. Tighten the nut to 35 ft. lbs. (48 Nm) while holding the lever in position and then rotate the lever back against the stop on the caliper.
  30.  
  31. Install the spring with the damper and then connect the parking brake cable.
  32.  
  33. Install the retaining clip onto the lever so that it prevents the parking brake cable from sliding out of the slot in the lever.
  34.  
  35. Adjust the parking brake cable by tightening the cable at the adjuster until the lever begins to move off the stop on the caliper. Loosen the adjustment just enough so that the lever moves back against the stop. Apply and release the parking brake three times to verify proper adjustment.
  36.  
  37. Remove the two lug nuts and then replace the wheels. Lower the vehicle.
  38.  
  39. Bleed the brake system and recheck the fluid level.
  40.  



Click image to see an enlarged view

Fig. Fig. 1: Exploded view of a rear disc caliper and parking brake assembly

OVERHAUL



  1. Remove the caliper from the car.
  2.  
  3. Secure the caliper in a vise.
  4.  
  5. Remove the two mounting sleeves and four bushings from the caliper and discard.
  6.  
  7. Remove the brake shoes and lever return spring.
  8.  

Pad the caliper using shop towels to catch the piston and brake fluid when removing the piston.

  1. Rotate the lever back and forth to move the piston out of the caliper housing.
  2.  

If the piston will not move out of the housing by rotating the lever, it can be turned out using a wrench. Remove the lock nut, lever, lever seal, and anti-friction washer. Using a wrench, turn the screw hex in normal parking brake apply direction until the piston pops out of the housing.

  1. Remove the piston assembly and balance spring.
  2.  
  3. Remove the locknut, lever, lever seal, and anti-friction washer.
  4.  
  5. Push screw out of the housing. Clean the screw with denatured alcohol or clean brake fluid.
  6.  
  7. Remove the piston seal and boot.
  8.  
  9. Flush the caliper housing with clean denatured alcohol to remove all contaminants.
  10.  
  11. All passages should be blown out with filtered compressed air.
  12.  

To assemble:
  1. Install a new piston seal.
  2.  
  3. Install a new boot onto the new piston assembly. The lip of the boot fits in a groove provided in the piston.
  4.  
  5. Assemble a new thrust washer so that the gray teflon bearing surface is against the cast iron housing and the seal onto the actuator screw. Lubricate the seal with clean brake fluid.
  6.  
  7. Fit the actuator screw in the piston assembly. Piston assemblies are stamped by a letter on the end of the adjuster screw "L" and "R". These letters should match the letter on the caliper housing.
  8.  
  9. Coat the new piston seal with a thin film of clean brake fluid.
  10.  
  11. Fit the balance spring into the piston assembly spring retainer and start the assembly into the caliper housing.
  12.  
  13. Use tool J-23072 to install the piton until it seats in the housing.
  14.  

The piston must be pushed in straight or the actuator screw seal will be damaged as it passes through the hole in the rear of the piston bore.

  1. Before removing tool J-23072, install the anti-friction washer, lubricated with silicone; a new lever seal; lever and locknut.
  2.  

Install the lever away from the stop. Rotate in the apply direction and hold in position. Torque the nut to 25 ft. lbs. (34 Nm).

  1. Remove tool J-23072, rotate lever back to the stop.
  2.  
  3. Using tool J-28678, drive the boot until the seal bottoms in the housing.
  4.  
  5. Install the shoe and the linings.
  6.  
  7. Install the caliper.
  8.  

 
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