GM Full Size Vans 1967-1986 Repair Guide

Caliper

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REMOVAL & INSTALLATION



See Figures 1 through 9



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Fig. Fig. 1: Exploded view of the brake caliper and pads



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Fig. Fig. 2: Use a C-clamp to push the piston back into the caliper



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Fig. Fig. 3: Loosen and remove the caliper bolts ...



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Fig. Fig. 4: ... then remove the caliper from the rotor



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Fig. Fig. 5: Remove the brake pads from the caliper assembly



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Fig. Fig. 6: Hang the caliper with a piece of wire. If necessary, detach the brake hose



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Fig. Fig. 7: Lubricate the caliper bolts before installation



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Fig. Fig. 8: View of the caliper lubrication points



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Fig. Fig. 9: Installing the support spring

  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.
  2.  
  3. Raise and support the vehicle. Remove the front wheels and tires.
  4.  
  5. Push the brake piston back into its bore using a C-clamp to pull the caliper outward.
  6.  
  7. Remove the two bolts which hold the caliper and then lift the caliper off the disc.
  8.  


WARNING
Do not let the caliper assembly hang by the brake hose.

  1. Remove the inboard and outboard shoe.
  2.  

If the pads are to be reinstalled, mark them inside and outside.

  1. Remove the pad support spring from the piston.
  2.  
  3. Remove the two sleeves from the inside ears of the caliper and the 4 rubber bushings from the grooves in the caliper ears.
  4.  
  5. Remove the hose from the steel brake line and tape the fittings to prevent foreign material from entering the line or the hoses.
  6.  
  7. Remove the retainer from the hose fitting.
  8.  
  9. Remove the hose from the frame bracket and pull off the caliper with the hose attached.
  10.  

Check the inside of the caliper for fluid leakage; if so, the caliper should be overhauled.


WARNING
Do not use compressed air to clean the inside of the caliper as this may unseat the dust boot.

  1. Connect the brake line to start reinstallaiton. Lubricate the sleeves, rubber bushings, bushing grooves, and the end of the mounting bolts using silicone lubricant.
  2.  
  3. Install new bushing in the caliper ears along with new sleeves. The sleeve should be replaced so that the end toward the shoe is flush with the machined surface of the ear.
  4.  
  5. Position the support spring and the inner pad into the center cavity of the piston. The outboard pad has ears which are bent over to keep the pad in position while the inboard pad has ears on the top end which fit over the caliper retaining bolts. A spring which is inside the brake piston hold the bottom edge of the inboard pad.
  6.  
  7. Push down on the inner pad until it lays flat against the caliper. It is important to push the piston all the way into the caliper if new linings are installed or the caliper will not fit over the rotor.
  8.  
  9. Position the outboard pad with the ears of the pad over the caliper ears and the tab at the bottom engaged in the caliper cutout.
  10.  
  11. With the two pads in position, place the caliper over the brake disc and align the holes in the caliper with those of the mounting bracket.
  12.  


WARNING
Make certain that the brake hose is not twisted or kinked.

  1. Install the 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 on the inboard pad.
  2.  
  3. Tighten the mounting bolts to 35 ft. lbs. (47 Nm). Pump the brake pedal to seat the pad against the rotor. Don't do this unless both calipers are in place. Use a pair of channel lock pliers to bend over the upper ears of the outer pad so it isn't loose.
  4.  
  5. Install the front wheel and lower the truck.
  6.  
  7. Add fluid to the master cylinder reservoirs so that they are 1 / 4 in. (6.35mm) from the top.
  8.  
  9. Test the brake pedal by pumping it to obtain a hard pedal. Check the fluid level again and add fluid as necessary. Do not move the vehicle until a hard pedal is obtained.
  10.  

OVERHAUL



See Figures 10 through 14



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Fig. Fig. 10: Apply a small amount of compressed air to push the piston out



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Fig. Fig. 11: Grasp the piston and remove it from the caliper bore



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Fig. Fig. 12: Use extreme caution when removing the piston seal; DO NOT scratch the caliper bore



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Fig. Fig. 13: Remove the boot from the caliper housing, taking care not to score or damage the bore



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Fig. Fig. 14: View of the disassembled caliper and components


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 and then apply compressed air to the caliper inlet hose.
  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 screwdriver. Use caution when performing this procedure.
  2.  
  3. Remove the piston seal from the caliper piston bore using a small piece of wood or plastic. DO NOT use any type of metal tool for this procedure.
  4.  
  5. Remove the bleeder valve from the caliper.
  6.  
  7. Clean all parts in the recommended solvent and dry them completely using compressed air if possible.
  8.  

The use of shop air hoses may inject oil film into the assembly; use caution when using such hoses.

  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 them as necessary.
  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. 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 in the same manner 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 unseat the seal. Force the piston to the bottom of the bore.
  8.  
  9. Place the dust boot in the caliper counterbore and seat the boot. Make sure that the boot in positioned correctly and evenly.
  10.  
  11. Install the brake hose in the caliper inlet using a new copper gasket.
  12.  

The hose must be positioned in the caliper locating gate to assure proper positioning of the caliper.

  1. Replace the bleeder screw.
  2.  
  3. Bleed the system.
  4.  

 
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