GM S-Series Pick-ups and SUV's 1994-1999 Repair Guide

Brake Caliper

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REMOVAL & INSTALLATION




CAUTION
Brake pads may 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.

Front Caliper

A scan tool is absolutely necessary to bleed the brake hydraulic system on models equipped with an Anti-lock Brake System (ABS). If your vehicle is equipped with ABS, be sure to refer to the ABS bleeding procedures in this section before performing any work on your vehicle's brake hydraulic system.

  1. If the fluid reservoir is full, siphon off about 2 / 3 of the brake fluid from the master cylinder reservoirs in order to prevent the possibility of spillage when the caliper pistons are bottomed. A common kitchen turkey baster may also be used to remove brake fluid, but make sure the tool is clean before inserting it in the reservoir.
  2.  
  3. Raise and support the vehicle safely using jackstands.
  4.  
  5. Remove the tire and wheel assemblies.
  6.  
  7. If equipped, remove the ABS sensor wire retainer.
  8.  
  9. Install a C-clamp on the caliper so that the solid frame side of the clamp rests against the back of the caliper and the driving screw end rests against the metal part (center backing plate) of the outboard pad. Tighten the clamp until the caliper moves sufficiently to bottom the piston in its bore, then remove the clamp.
  10.  
  11. Remove the two caliper mounting bolts from the back of the caliper. If the caliper is not being completely removed from the vehicle, remove it from the mounting bracket and support it from the suspension using a coat hanger or length of wire. Do not allow the hose to be stretched, twisted, kinked or otherwise damaged.
  12.  
  13. If the caliper is being completely removed from the vehicle, disconnect the flexible brake hose-to-caliper banjo-bolt, discard the pressure fitting washers (they must be replaced with new ones during assembly), then remove the brake caliper from the vehicle and place it on a work bench.
  14.  
  15. To inspect the caliper assembly, perform the following procedures:
    1. Check the inside of the caliper assembly for pitting or scoring. If heavy scoring or pitting is present, caliper replacement is recommended.
    2.  
    3. Check the mounting bolts and sleeves for signs of corrosion; if necessary, replace the bolts.
    4.  

  16.  

If the mounting bolts have signs of corrosion, DO NOT attempt to polish away the corrosion. Instead the bolts must be replaced to assure proper caliper sliding and prevent the possibility of brake drag or locking.

To install:
  1. Lubricate and position the caliper bushings and sleeves. Apply Delco® silicone lube or equivalent to lubricate the mounting bolts.
  2.  
  3. With both pads installed to the caliper, place the caliper over the disc, lining up the hole in the caliper ears with the holes in the mounting bracket.
  4.  
  5. If the caliper was completely removed, install the flexible hose to the caliper and secure using the banjo bolt and new washers. Make sure that the brake hose is not twisted or kinked, then tighten the bolt to 32 ft. lbs. (44 Nm).
  6.  
  7. Carefully insert the mounting bolts through the bracket and caliper (bushing and sleeves), then tighten to 37 ft. lbs. (50 Nm) on all except 1998-99 4 wheel disc models. On 4 wheel disc models, tighten the bolts to 77 ft. lbs. (105 Nm).
  8.  
  9. If removed, install the ABS sensor wire retainer and tighten the bolt to 13 ft. lbs. (17 Nm).
  10.  
  11. Pump the brake pedal a few times to seat the linings against the rotors.
  12.  
  13. Use a pair of channel lock pliers to compress the pad ears so no clearance exists between the pad ears and the caliper.
  14.  
  15. Check the clearance between the caliper and steering knuckle. Clearance at each end of the caliper should be measured individually and the results added together. Clearance should not exceed 0.010-0.024 in. (0.026-0.60mm).
  16.  
  17. Install the wheels, then remove the jackstands and carefully lower the vehicle.
  18.  
  19. Check and refill the master cylinder reservoirs with brake fluid.
  20.  


CAUTION
DO NOT attempt to move the vehicle until a firm brake pedal is obtained.

  1. Properly bleed the hydraulic brake system. If only a caliper fitting was disconnected, bleeding of the entire system should not be required. Bleed air from the system at the caliper that was disconnected. Check the system for proper operation. If air remains in the system, bleeding at all points in the system may be required.
  2.  

Rear Caliper

A scan tool is absolutely necessary to bleed the brake hydraulic system on models equipped with an Anti-lock Brake System (ABS). If your vehicle is equipped with ABS, be sure to refer to the ABS bleeding procedures in this section before performing any work on your vehicle's brake hydraulic system.

  1. Raise and support the vehicle safely using jackstands.
  2.  
  3. Remove the tire and wheel assemblies.
  4.  
  5. Remove the two caliper mounting bolts from the back of the caliper. If the caliper is not being completely removed from the vehicle, remove it from the mounting bracket and support it from the suspension using a coat hanger or length of wire. Do not allow the hose to be stretched, twisted, kinked or otherwise damaged.
  6.  
  7. If the caliper is being completely removed from the vehicle, disconnect the flexible brake hose-to-caliper banjo-bolt, discard the pressure fitting washers (they must be replaced with new ones during assembly), then remove the brake caliper from the vehicle and place it on a work bench.. Plug the hole in the caliper and the cap the brake line to prevent contamination of the system.
  8.  
  9. To inspect the caliper assembly, perform the following procedures:
    1. Check the inside of the caliper assembly for pitting or scoring. If heavy scoring or pitting is present, caliper replacement is recommended.
    2.  

  10.  

If the mounting bolts have signs of corrosion, DO NOT attempt to polish away the corrosion. Instead the bolts must be replaced to assure proper caliper sliding and prevent the possibility of brake drag or locking.

To install:
  1. With both pads installed to the caliper, place the caliper over the disc, lining up the hole in the caliper ears with the holes in the mounting bracket.
  2.  
  3. If the caliper was completely removed, install the flexible hose to the caliper and secure using the banjo bolt and new washers. Make sure that the brake hose is not twisted or kinked, then tighten the bolt to 27 ft. lbs. (20 Nm).
  4.  
  5. Carefully insert the mounting bolts through the bracket and caliper (bushing and sleeves), then tighten to 23 ft. lbs. (31 Nm).
  6.  
  7. Pump the brake pedal a few times to seat the linings against the rotors.
  8.  
  9. Install the wheels, then remove the jackstands and carefully lower the vehicle.
  10.  
  11. Check and refill the master cylinder reservoirs with brake fluid.
  12.  


CAUTION
DO NOT attempt to move the vehicle until a firm brake pedal is obtained.

  1. Properly bleed the hydraulic brake system if a brake hose fitting was disconnected. If no hoses were disconnected, no bleeding should be required. Bleed air from the system at the caliper that was disconnected. Check the system for proper operation. If air remains in the system, bleeding at all points in the system may be required.
  2.  

OVERHAUL



See Figures 1 through 8

A scan tool is absolutely necessary to bleed the brake hydraulic system on models equipped with an Anti-lock Brake System (ABS). If your vehicle is equipped with ABS, be sure to refer to the ABS bleeding procedures in this section before performing any work on your vehicle's brake hydraulic system.

Some vehicles may be equipped dual piston calipers. The procedure to overhaul the caliper is essentially the same with the exception of multiple pistons, O-rings and dust boots.

  1. Remove the caliper from the vehicle and place on a clean workbench.
  2.  


CAUTION
NEVER place your fingers in front of the pistons in an attempt to catch or protect the pistons when applying compressed air. This could result in personal injury!

Depending upon the vehicle, there are two different ways to remove the piston from the caliper. Refer to the brake pad replacement procedure to make sure you have the correct procedure for your vehicle.

  1. The first method is as follows:
    1. Stuff a shop towel or a block of wood into the caliper to catch the piston.
    2.  
    3. Remove the caliper piston using compressed air applied into the caliper inlet hole. Inspect the piston for scoring, nicks, corrosion and/or worn or damaged chrome plating. The piston must be replaced if any of these conditions are found.
    4.  

  2.  



Click image to see an enlarged view

Fig. Fig. 1: For some types of calipers, use compressed air to drive the piston out of the caliper, but make sure to keep your fingers clear



Click image to see an enlarged view

Fig. Fig. 2: Withdraw the piston from the caliper bore

  1. For the second method, you must rotate the piston to retract it from the caliper.
  2.  
  3. If equipped, remove the anti-rattle clip.
  4.  



Click image to see an enlarged view

Fig. Fig. 3: On some vehicles, you must remove the anti-rattle clip

  1. Use a prytool to remove the caliper boot, being careful not to scratch the housing bore.
  2.  



Click image to see an enlarged view

Fig. Fig. 4: Use a prytool to carefully pry around the edge of the boot ...



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Fig. Fig. 5: ... then remove the boot from the caliper housing, taking care not to score or damage the bore

  1. Remove the piston seals from the groove in the caliper bore.
  2.  



Click image to see an enlarged view

Fig. Fig. 6: Use extreme caution when removing the piston seal; DO NOT scratch the caliper bore

  1. Carefully loosen the brake bleeder valve cap and valve from the caliper housing.
  2.  
  3. Inspect the caliper bores, pistons and mounting threads for scoring or excessive wear.
  4.  
  5. Use crocus cloth to polish out light corrosion from the piston and bore.
  6.  
  7. Clean all parts with denatured alcohol and dry with compressed air.
  8.  

To assemble:
  1. Lubricate and install the bleeder valve and cap.
  2.  
  3. Install the new seals into the caliper bore grooves, making sure they are not twisted.
  4.  
  5. Lubricate the piston bore.
  6.  
  7. Install the pistons and boots into the bores of the calipers and push to the bottom of the bores.
  8.  
  9. Use a suitable driving tool to seat the boots in the housing.
  10.  



Click image to see an enlarged view

Fig. Fig. 7: Use the proper size driving tool and a mallet to properly seal the boots in the caliper housing

  1. Install the caliper in the vehicle.
  2.  
  3. Install the wheel and tire assembly, then carefully lower the vehicle.
  4.  
  5. Properly bleed the brake system.
  6.  



Click image to see an enlarged view

Fig. Fig. 8: There are tools, such as this Mighty-Vac, available to assist in proper brake system bleeding

 
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