GM Full-Size Trucks 1970-1979 Repair Guide

Disc Brake Caliper

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REMOVAL & INSTALLATION



See Figures 1 through 9



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Fig. Fig. 1: View of the Bendix brake components



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Fig. Fig. 2: Use a clean turkey baster remove some brake fluid from the reservoir



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Fig. Fig. 3: Press the caliper piston into its bore using a C-clamp



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Fig. Fig. 4: For Bendix brakes, remove the caliper support key



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Fig. Fig. 5: For Delco brakes, unfasten ...



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Fig. Fig. 6: ... then remove the two Allen head bolts



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Fig. Fig. 7: If the caliper is being removed for replacement or overhaul, unfasten ...



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Fig. Fig. 8: ... then remove the brake fluid hose from the caliper



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Fig. Fig. 9: Caliper lubrication points

  1. Remove the cover on the master cylinder and siphon enough fluid out of the reservoirs to bring the level to 1 / 3 full. This step prevents spilling fluid when the piston is pushed back. Discard the fluid.
  2.  
  3. Raise and safely support the vehicle. Remove the front wheels and tires.
  4.  
  5. Push the brake piston back into its bore using a C-clamp.
  6.  
  7. If equipped with Delco, brakes remove the two Allen head bolts which hold the caliper and then lift the caliper off the disc.
  8.  
  9. If equipped with Bendix brakes, remove the bolt at the caliper support key. Use a brass drift pin to remove the key and spring.
  10.  


WARNING
Do not let the caliper assembly hang by the brake hose. Tie it out of the way with wire.

  1. If the caliper is being removed for replacement or overhaul, disconnect the brake hose and remove the caliper from the vehicle.
  2.  

To install:
  1. For Delco brakes perform the following:
    1. Position the caliper over the rotor, lining up the holes in the caliper ears with the holes in the mounting bracket.
    2.  
    3. Install the bolts starting through the inboard caliper sleeves and ears and through the mounting bracket, making sure the ends of the bolts pass under the retaining ears on the inboard shoe. Push the bolts on through to engage the holes in the outboard shoes and the outboard caliper ears at the same time, threading the bolts into the mounting bracket. Tighten the bolts to 35 ft. lbs.
    4.  

  2.  
  3. For Bendix brakes, perform the following:
    1. Position the caliper over the brake disc, guiding the upper caliper groove onto the mating surface of the steering knuckle or caliper support. Position the caliper to the lower steering knuckle (or support) sliding surface.
    2.  
    3. Place the spring over the caliper support key, install the assembly between the steering knuckle (or rear support) and lower caliper groove. Tap into place until the key retaining screw can be installed, using a brass punch and a light hammer.
    4.  
    5. Install the screw and tighten to 12-18 ft. lbs. The boss must not fit fully into the circular cutout in the key.
    6.  

  4.  
  5. If the brake hose was disconnected, bleed the brake system as outlined in this section.
  6.  
  7. Add fresh brake fluid as necessary to the master cylinder.
  8.  
  9. Install the wheel and tire assemblies, then carefully lower the vehicle.
  10.  
  11. Pump the brake pedal to seat the linings against the rotor.
  12.  

OVERHAUL



See Figures 10 through 18



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Fig. Fig. 10: Use compressed air to blow the piston out of the caliper



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Fig. Fig. 11: Remove the piston from the bore



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Fig. Fig. 12: Carefully pry the boot out of the piston bore



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Fig. Fig. 13: Use EXTREME caution when removing the piston seal. DO NOT scratch the caliper bore



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Fig. Fig. 14: During assembly, use a suitable piston boot driver to properly install the boot to the housing



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Fig. Fig. 15: Proper piston boot seating



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Fig. Fig. 16: Exploded view of the Delco brake caliper assembly



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Fig. Fig. 17: Exploded view of the Bendix brake caliper assembly



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Fig. Fig. 18: Cross-sectional view of a front disc brake caliper


WARNING
Use only denatured alcohol or brake fluid to clean caliper parts. Never use any mineral based cleaning solvents such as gasoline or kerosene as these solvents will deteriorate rubber parts.

  1. Remove the caliper, clean it and place it on a clean and level work surface.
  2.  
  3. Remove the brake hose from the caliper and discard the copper gasket. Check the brake hose for cracks or deterioration. Replace the hose as necessary.
  4.  
  5. Drain the brake fluid from the caliper.
  6.  
  7. Pad the interior of the caliper with cloth or a piece of wood, and then apply compressed air to the caliper inlet hole.
  8.  


CAUTION
Do not place hands or fingers in front of the piston in an attempt to catch it. Use just enough air pressure to ease the piston out of the bore.

  1. Remove the piston dust boot by prying it out with a drift pin. Use caution when performing this procedure.
  2.  
  3. Remove the piston seal from the caliper piston bore.
  4.  
  5. Remove the bleeder valve from the caliper.
  6.  

Dust boot, piston seal, rubber bushings and sleeves are included in every rebuilding kit. These should be replaced at every caliper rebuilt.

  1. Clean all parts in solvent and dry them completely.
  2.  


WARNING
The use of lubricated shop air may leave an oil film on metal parts. This may damage rubber parts.

  1. Examine the mounting bolts for rust or corrosion. Replace them as necessary.
  2.  
  3. Examine the piston for scoring, nicks, or worn plating. If any of these conditions are present, replace the piston.
  4.  


WARNING
Do not use any type of abrasive on the piston.

  1. Check the piston bore. Small defects can be removed with crocus cloth. (Do not use emery cloth.) If the bore cannot be cleaned in this manner, replace the caliper.
  2.  
  3. Lubricate the piston bore and the new piston seal with brake fluid. Place the seal in the caliper bore groove.
  4.  
  5. Lubricate the piston and position the new boot into the groove in the piston so that the fold faces the open end of the piston.
  6.  
  7. Place the piston into the caliper bore using caution not to damage the seal. Force the piston to the bottom of the bore. This will require a force of 50-100 lbs.
  8.  
  9. Place the dust boot in the caliper counterbore and seat the boot. Make sure that the boot is positioned correctly and evenly. Proper seating of the boot is very important for sealing out contaminants.
  10.  
  11. Lubricate the new sleeves and rubber bushings. Install the bushings in the caliper ears. Install the sleeves so that the end toward the disc pad is flush with the machined surface.
  12.  

Lubrication of the sleeves and bushings is essential to ensure the proper operation of the sliding caliper design.

  1. Install the shoe support spring in the piston.
  2.  
  3. Install the disc pads in the caliper and remount the caliper in the hub.
  4.  
  5. Reconnect the brake hose to the steel brake line. Install the retainer clip. Bleed the brakes.
  6.  
  7. Replace the wheels, check the brake fluid level, check the brake pedal travel, and road test the vehicle.
  8.  

 
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