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

Brake Pads

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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.

INSPECTION



See Figures 1, 2 and 3

Brake pads should be inspected once a year or at 6000 miles (9600 km), whichever occurs first or every time the wheel is removed. Check both ends of the outboard pad, looking in at each end of the caliper; then check the lining thickness of the inboard pad, looking down through the inspection hole. On riveted pads, the lining should be more than 0.030 in. (0.76mm) thick above the rivet (so that the lining is thicker than the metal backing in most cases) in order to prevent the rivet from scoring the rotor. On bonded brake pads, a minimum lining thickness of 0.030 in. (0.76mm) above the backing plate should be used to determine necessary replacement intervals. Keep in mind that any applicable state inspection standards that are more stringent take precedence. All four pads MUST be replaced as a set if one shows excessive wear.



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Fig. Fig. 1: The brake lining can be checked through a opening in the brake caliper housing



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Fig. Fig. 2: Relative size differences between a new and worn pad lining



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Fig. Fig. 3: The brake pads have a wear indicator which touches the brake rotor when the pad lining is worn and makes a loud metal-to-metal squealing noise. Once this happens the pads should be replaced

All models should be equipped with a wear indicator that makes a noise when the linings have worn to a degree where replacement is necessary. The spring clip is an integral part of the inboard pad and lining. When the brake pad reaches a certain degree of wear, the clip will contact the rotor and produce a warning noise.

REMOVAL & INSTALLATION



See Figures 4 through 11



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Fig. Fig. 4: If the fluid reservoir is full, siphon some fluid from the reservoirs to prevent spillage



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Fig. Fig. 5: View of a common front disc brake system



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Fig. Fig. 6: On models equipped with front disc brakes, use a C-clamp to bottom the piston in the caliper bore



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Fig. Fig. 7: On models equipped with front disc brakes, loosen the caliper mounting bolts/pins



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Fig. Fig. 8: On models equipped with front disc brakes, remove the caliper mounting bolts



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Fig. Fig. 9: On models equipped with front disc brakes, after removing the caliper, support the weight of the caliper with mechanics wire or a coat hanger.



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Fig. Fig. 10: On models equipped with front disc brakes, remove the outboard pad from the caliper



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Fig. Fig. 11: On models equipped with front disc brakes, remove the inboard pad from the caliper piston

The following procedure requires the use of a C-clamp and on front disc brakes a pair of channel lock pliers.

  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.  


WARNING
The insertion of thicker replacement pads will push the piston back into its bore and will cause a full master cylinder reservoir to overflow, possibly causing paint damage. In addition to siphoning off fluid, keep the reservoir cover on during pad replacement.

  1. Raise and support the vehicle safely using jackstands.
  2.  
  3. Remove the necessary tire and wheel assemblies.
  4.  

Replacing the pads on just one wheel may cause uneven braking; always replace the pads on both wheels.

  1. 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.
  2.  
  3. Tighten the clamp until the caliper moves sufficiently to bottom the piston in its bore, then remove the clamp.
  4.  

See Figure 12



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Fig. Fig. 12: Exploded view of a common caliper and brake pad assembly

  1. On models equipped with front disc brakes, perform the following steps for pad removal:
    1. Remove the two Allen head caliper mounting bolts from the back of the caliper.
    2.  
    3. Remove the caliper from the mounting bracket and support from the vehicle's suspension using a coat hanger or length of wire. Do not allow the brake line to support the caliper's weight and be sure the line is not otherwise kinked or damaged.
    4.  
    5. Remove the inboard and outboard pads from the caliper.
    6.  
    7. Remove the inboard pad spring clip from the piston or pad. Remove the spring clip carefully as it must be reused upon installation of the new pads.
    8.  
    9. Remove the bolt ear sleeves and rubber bushings for cleaning, inspection and lubrication.
    10.  

  2.  
  3. On models equipped with rear disc brakes, perform the following steps for pad removal:
    1. Using a back-up wrench, loosen the top caliper mounting bolt and remove the bottom bolt.
    2.  
    3. Grasp the bottom of the caliper and rotate the caliper upwards to access the brake pads. In some cases it may be necessary to unfasten both caliper retaining bolts and remove the caliper. If the caliper must be removed, support it from the vehicle's suspension or frame using a coat hanger or length of wire. Do not allow the brake line to support the caliper's weight and be sure the line is not otherwise kinked or damaged.
    4.  
    5. Remove the inboard and outboard pads from the caliper.
    6.  
    7. Remove the pad spring shim, if equipped.
    8.  

  4.  
  5. Check the rotor for cracks, excessive scoring and lateral run-out. Refer to the procedure outlined in this section.
  6.  

See Figures 13 through 20



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Fig. Fig. 13: On models equipped with rear disc brakes, using a back-up wrench, loosen the top caliper mounting bolt and remove the bottom bolt ...



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Fig. Fig. 14: ... then grasp the bottom of the caliper and rotate the caliper upwards to access the brake pads



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Fig. Fig. 15: On models equipped with rear disc brakes, once the caliper is out of the way, the pads are easily removed

To install:
  1. Check the inside of the caliper for leakage and the condition of the piston dust boot. If necessary, remove the caliper and overhaul or replace it.
  2.  
  3. Lubricate the sleeves and bushings using a suitable silicone lubricant, and if removed, then install them.
  4.  
  5. Make sure the piston is fully bottomed in the caliper providing clearance for the new brake pads. If the piston is not compressed, install the old inboard pad and use the C-clamp on the pad and back on the caliper to bottom the piston. Be careful not to pinch and damage the piston boot.
  6.  



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Fig. Fig. 16: On models equipped with rear disc brakes, the spring clip must be properly installed on the inboard pad



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Fig. Fig. 17: On models equipped with rear disc brakes, install the inboard pad to the caliper by carefully inserting the spring clip in the piston



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Fig. Fig. 18: On models equipped with rear disc brakes, position the outboard pad over the caliper ears



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Fig. Fig. 19: On models equipped with rear disc brakes, compress the brake pad ears using a pair of channel lock pliers



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Fig. Fig. 20: On models equipped with rear disc brakes, when the caliper is installed, check for proper caliper-to-knuckle bracket clearance

  1. On models equipped with front disc brakes, install the pad assembly as follows:
    1. Install the spring clip to the inboard pad, then install the pad to the caliper.Make sure that the wear sensor is facing in the proper direction. On most vehicles it should face toward the rear of the caliper.
    2.  
    3. Place the outboard pad in the caliper with its top ears over the caliper ears and the bottom tab engaged in the caliper cutout.
    4.  
    5. Place the caliper over the disc, lining up the hole in the caliper ears with the holes in the mounting bracket. Make sure that the brake hose is not twisted or kinked.
    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.  

  2.  
  3. Use a pair of channel lock pliers to compress the pad ears so no clearance exists between the pad ears and the caliper.
  4.  
  5. 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).
  6.  
  7. On models equipped with rear disc brakes, install the pads as follows:
    1. If removed, install the pad spring shim, then install the pads.
    2.  
    3. If removed, place the caliper over the disc, lining up the hole in the caliper ears with the holes in the mounting bracket. Make sure that the brake hose is not twisted or kinked.
    4.  
    5. If the caliper was not removed, rotate it back into position and install the mounting bolt. Tighten the bolt(s) to 23 ft. lbs. (31 Nm).
    6.  

  8.  
  9. Pump the brake pedal a few times to seat the linings against the rotors.
  10.  
  11. Install the wheels, then remove the jackstands and carefully lower the vehicle.
  12.  
  13. Check and refill the master cylinder reservoirs with brake fluid.
  14.  


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

  1. Pump the brake pedal to make sure that it is firm. If necessary, bleed the brakes.
  2.  

 
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