GM Astro/Safari 1985-1996 Repair Guide

Brake Caliper

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REMOVAL & INSTALLATION




CAUTION
Brake shoes contain asbestos, which has been determined to be a cancer causing agent. Never clean the brake surfaces with compressed air! Avoid inhaling any dust from any brake surface! When cleaning brake surfaces, use a commercially available brake cleaning fluid.

See Figures 1, 2 and 3



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Fig. Fig. 1: The caliper bolts must pass under the pad retaining ears



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Fig. Fig. 2: Check the clearance between the caliper and caliper mount. The numbers shown are total clearance, not individual sides-Two wheel drive



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Fig. Fig. 3: Check the clearance between the caliper and caliper mount. The numbers shown are total clearance, not individual sides-All wheel drive

  1. Remove the brake caliper from the steering knuckle.
  2.  
  3. Disconnect the flexible brake hose-to-caliper bolt, discard the pressure fitting washers, then remove the brake caliper from the vehicle and place it on a work bench.
  4.  
  5. To inspect the caliper assembly, perform the following procedures:
    1. Check the inside of the caliper assembly for signs of leakage; if necessary, replace or rebuild the caliper.
    2.  
    3. Check the mounting bolts and sleeves for signs of corrosion; if necessary, replace the bolts.
    4.  

  6.  

If the mounting bolts have signs of corrosion, DO NOT attempt to polish away the corrosion.

To install:
  1. Use new caliper bushings and sleeves, use Delco® Silicone Lube or equivalent to lubricate the mounting bolts and new brake pads (if necessary).
  2.  
  3. After both pads are installed, lift the caliper and place the bottom edge of the outboard pad on the outer edge of the disc to make sure that there is no clearance between the tab on the bottom of the shoes and the caliper abutment.
  4.  
  5. Place the caliper over the disc, lining up the hole in the caliper ears with the hole in the mounting bracket.
  6.  
  7. Start the caliper-to-mounting bracket bolts through the sleeves in the inboard caliper ears and through the mounting bracket, making sure that the ends of the bolts pass under the retaining ears of the inboard shoe.
  8.  
  9. Push the mounting bolts through to engage the holes in the outboard shoes and the outboard caliper ears, then thread them into the mounting bracket.
  10.  
  11. To complete the installation, use new flexible brake hose-to-caliper washers. Torque the caliper-to-steering knuckle bolts to 30-45 ft. lbs. (41-61 Nm) and the flexible brake hose-to-caliper bolt to 18-30 ft. lbs. (25-41 Nm). Refill the master cylinder reservoirs and bleed the brake system. Pump the brake pedal to seat the linings against the rotors.
  12.  
  13. Using a pair of slip-joint locking pliers, place them on the caliper housing notch, bend the caliper upper ears until no clearance exists between the shoe and the caliper housing.
  14.  
  15. Install the wheels, lower the vehicle. Pump the brake pedal to make sure that it is firm. Road test the vehicle.
  16.  

OVERHAUL



See Figures 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15



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Fig. Fig. 4: Exploded view of a brake caliper



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Fig. Fig. 5: Use low pressure compressed air to remove the piston, but be sure to pad the opposite side of the caliper to prevent the piston from flying out ...



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Fig. Fig. 6: ... a block of wood provides a suitable protective cushion for the piston



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Fig. Fig. 7: Pull the piston out and away from the dust boot



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Fig. Fig. 8: Check the surface of the piston for damage and corrosion



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Fig. Fig. 9: Inspect the caliper for obvious defects before continuing the rebuild



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Fig. Fig. 10: Use a small prytool to remove the dust boot



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Fig. Fig. 11: The dust seal needs to be replaced every time it is removed



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Fig. Fig. 12: Be careful when removing the piston seal not to nick or scratch the bore and seal seating area



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Fig. Fig. 13: Use a proper tool, such as this, to install the dust boot ...



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Fig. Fig. 14: ... using a dust boot tool will help make sure the boot is properly seated



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Fig. Fig. 15: Before installation, check that the old crush gasket isn't stuck at the inlet port

  1. Remove the brake caliper from the vehicle.
  2.  
  3. Remove the inlet fitting from the brake caliper. Cap all openings to prevent system contamination or excessive fluid leakage.
  4.  
  5. Position the caliper on a work bench and place clean shop cloths in the caliper opening. Using compressed air, force the piston from its bore.
  6.  


CAUTION
DO NOT apply too much air pressure to the bore, for the piston may jump out, causing damage to the piston and/or the operator.

  1. Remove and discard the piston boot and seal (with a plastic or wooden tool).
  2.  
  3. Clean all of the parts with non-mineral based solvent and blow dry with compressed air. Replace the rubber parts with those in the brake service kit.
  4.  
  5. Inspect the piston and the caliper bore for damage or corrosion. Replace the caliper and/or the piston (if necessary).
  6.  
  7. Remove the bleeder screw and its rubber cap.
  8.  
  9. Inspect the guide pins for corrosion, replace them (if necessary). When installing the guide pins, coat them with silicone grease.
  10.  
  11. To install, perform the following procedures:
    1. Maintain the proper tolerances.
    2.  
    3. Lubricate the piston, caliper and seal with clean brake fluid and install those parts.
    4.  

  12.  

When positioning the piston dust boot on the piston, it goes in the groove nearest the piston's flat end with the lap facing the largest end. If placement is correct, the seal lips will be in the groove and not extend over the groove's step.

  1. Replace the mounting bolts and torque to 22-25 ft. lbs. (30-34 Nm).
  2.  
  3. Bleed the brake system after installation and pump the pedal before moving the vehicle.
  4.  

 
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