GM Century/Lumina/Grand Prix/Intrigue 1997-2000

Brake Caliper

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REMOVAL & INSTALLATION



Front
  1. Using a clean suction gun, remove approximately 2 / 3 of the brake fluid from the master cylinder. The reason for this is that the caliper pistons must be pushed back into their bores so the caliper can be removed from the rotor. This could cause the brake fluid to overflow from the reservoir onto painted surfaces or wiring.
  2.  
  3. Raise and safely support the vehicle on safety stands.
  4.  
  5. Mark the relationship of the wheel to the hub so it can later be installed in the same relationship. This helps retain the balance of the rotating assembly.
  6.  
  7. Remove the front tire and wheel assembly. Install two wheel lug nuts to keep the rotor on the hub.
  8.  
  9. Push the caliper piston(s) back into their bore(s) to provide clearance between the linings and rotor. Use a large C-clamp over the top of the caliper housing and against the back of the outboard pad. Slowly tighten the C-clamp until the piston(s) are pushed back into the caliper bore(s) enough to slide the caliper off the rotor.
  10.  
  11. Remove the brake hose bolt from the caliper end of the hose. There should be copper seal washers on each side of the hose fitting. Plug the openings in the brake hose to keep the brake fluid reservoir from draining.
  12.  
  13. Remove the caliper slide pin bolts and carefully work the caliper away from the rotor and caliper mounting bracket.
  14.  

To install:

  1. Bottom the piston(s) in the caliper bore(s) using a C-clamp, if new brake pads are to be installed. Use a large C-clamp and a metal plate or wooden block across the face of the piston(s). Take care not to damage the piston(s) or caliper rubber dust boot(s). After bottoming the piston(s), carefully lift the inner edge of the caliper boot(s) next to the piston(s) and press out any trapped air. The boots must lay flat below the level of the piston face.
  2.  
  3. Install the brake pad using the procedures found in this section.
  4.  
  5. Install the caliper over the rotor and mounting bracket and work into place. Make sure the bushings in the caliper bracket are still in place.
  6.  
  7. Connect the brake hose using new copper seal washers. Tighten the bolt to 32 ft. lbs. (44 Nm).
  8.  
  9. Carefully lubricate the caliper mounting bolts (slide pins) using silicone grease. Do not lubricate the threads or the mounting bolts may tend to work loose. Install the caliper mounting bolts. Use a small flat-blade tool to push the pin boot over the shoulder of the mounting bolt. The pin boot must be securely in the groove of the mounting bolt. Torque the caliper mounting bolts to 80 ft. lbs. (108 Nm).
  10.  
  11. Install the tire and wheel assembly, aligning the balance marks made at removal.
  12.  
  13. Lower the vehicle.
  14.  
  15. Fill the master cylinder reservoir to the proper level using only fresh, clean DOT 3 brake fluid. Pump the brake pedal firmly to push the pistons back out into operating position and to seat the lining.
  16.  
  17. Bleed the brake system using the procedures found at the end of this section.
  18.  

Rear Disc Brake Calipers
WITH BUILT-IN PARKING BRAKE MECHANISM
  1. Using a suction gun, remove approximately 2 / 3 of the brake fluid from the master cylinder. The reason for this is that the caliper pistons must be pushed back into their bores so the caliper can be removed from the rotor. This could cause the brake fluid to overflow from the reservoir onto painted surfaces or wiring.
  2.  
  3. Raise and safely support the vehicle on safety stands.
  4.  
  5. Mark the relationship of the wheel to the hub so it can later be installed in the same relationship. This helps retain the balance of the rotating assembly.
  6.  
  7. Remove the rear tire and wheel assembly. Install two wheel lug nuts to keep the rotor on the hub.
  8.  
  9. Disconnect the brake line to the caliper. Plug the opening so all of the brake fluid does not drain from the master cylinder reservoir.
  10.  
  11. Remove the parking brake cable from the parking brake lever. Lift up on one end of the cable spring clip to free the end of the cable from the lever.
  12.  
  13. Remove the caliper slide pin bolts and carefully lift the caliper from its bracket.
  14.  

To install:

  1. Bottom the piston into the caliper bore noting the following:
    1. There is a special spanner-type tool designed to fit in the piston slots. This allows you to turn the piston and thread it into the caliper, retracting it. Use care if using a substitute tool. Careful work with suitable pliers may enable you to turn the piston back into its bore.
    2.  
    3. After bottoming the piston, lift the inner edge of the dust boot, next to the piston, and press out any trapped air. The boot must lay flat.
    4.  

  2.  
  3. Install the caliper to the mounting bracket, noting the following:
    1. If not replaced, remove the caliper mounting bolt boot from the caliper and install the small end over the tubular metal sleeve (installed on the caliper bracket). This is to prevent cutting the bolt boot when sliding the caliper body onto the sleeve.
    2.  
    3. Hold the caliper in position and start over the end of the sleeve. As the caliper approaches the boot, work the large end of the boot into the caliper groove. Then push the caliper fully onto the mounting bolt.
    4.  
    5. Pivot the caliper down, using care not to damage the piston dust boot on the inboard brake pad. Compress the mounting bolt boot by hand as the caliper moves into position to prevent boot damage.
    6.  
    7. After the caliper is in position, recheck the installation of the pad clips. If necessary, use a small flat-bladed tool to re-seat or center the pad clips on the mounting bracket.
    8.  
    9. Tighten the mounting bolts to 20 ft. lbs. (27 Nm).
    10.  

  4.  
  5. Install the cable support bracket. Connect the parking brake cable to the caliper lever. Lift up on the cable spring clip and work the end of the parking brake cable into the notch in lever.
  6.  
  7. Connect the brake fluid line. Use new copper washers, if equipped. Tighten the brake hose bolt to 32 ft. lbs. (44 Nm).
  8.  
  9. Install the tire and wheel assembly, aligning the balance marks made at removal.
  10.  
  11. Lower the vehicle.
  12.  
  13. Fill the master cylinder reservoir to the proper level using only fresh, clean DOT 3 brake fluid. Pump the brake pedal firmly to push the pistons back out into operating position and to seat the lining.
  14.  
  15. Bleed the brake system using the procedures found at the end of this section.
  16.  

WITHOUT BUILT-IN PARKING BRAKE MECHANISM
  1. Using a suction gun, remove approximately 2 / 3 of the brake fluid from the master cylinder. The reason for this is that the caliper pistons must be pushed back into their bores so the caliper can be removed from the rotor. This could cause the brake fluid to overflow from the reservoir onto painted surfaces or wiring.
  2.  
  3. Raise and safely support the vehicle on safety stands.
  4.  
  5. Mark the relationship of the wheel to the hub so it can later be installed in the same relationship. This helps retain the balance of the rotating assembly.
  6.  
  7. Remove the rear tire and wheel assembly. Install two wheel lug nuts to keep the rotor on the hub.
  8.  
  9. Install a large C-clamp over the brake caliper and against the back of the outboard brake pad. Tighten the C-clamp until the brake caliper piston pushes into the brake caliper bore enough to slide the caliper off the rotor. Remove the C-clamp.
  10.  
  11. Disconnect the brake line to the caliper. Plug the opening so all of the brake fluid does not drain from the master cylinder reservoir.
  12.  
  13. Remove the brake caliper mounting bolts
  14.  
  15. Remove the caliper from the mounting bracket.
  16.  

To install:

  1. Install the caliper upward in position. Use care not to damage the mounting bolt boots. Lubricate the mounting bolt and boot with silicone grease. Use care to keep grease off the mounting bolt threads to avoid having the mounting bolt loosen in service. Torque the mounting bolts to 33 ft. lbs. (45 Nm).
  2.  
  3. Install the brake line to the caliper. Use new copper seal washers, if equipped. Torque the brake hose bolt to 40 ft. lbs. (54 Nm).
  4.  
  5. Install the tire and wheel assembly, aligning the balance marks made at removal.
  6.  
  7. Lower the vehicle.
  8.  
  9. Fill the master cylinder reservoir to the proper level using only fresh, clean DOT 3 brake fluid. Pump the brake pedal firmly ( 3 / 4 of a full stroke) as many times as necessary to push the piston back out into operating position, seat the linings and obtain a firm brake pedal.
  10.  
  11. Bleed the brake system using the procedures found at the end of this section.
  12.  


CAUTION
Do not move the vehicle until a firm brake pedal is obtained. Air in the brake system can cause the loss of brakes with possible personal injury.

OVERHAUL



The decision to overhaul a brake caliper depends on the condition of the caliper and its components, and parts cost and availability. In many cases, a rebuilt brake caliper may be available at slightly more than the cost of overhaul parts, especially if the piston must be replaced. Many professional technicians simply exchange a worn out caliper for a rebuilt unit. This saves time and gets the vehicle back into service in the shortest amount of time. In addition, the rebuilt caliper generally has to pass a factory quality test so there is at least some sort of guarantee in case it leaks or there is some problem with the unit.

If the caliper is to be overhauled, compressed air is almost an absolute necessity to get the piston(s) out of the caliper body without damaging either component.

Front

The following sequence shows a typical dual-piston front caliper being disassembled for inspection and overhaul. The overhaul procedure for a single piston front caliper and a rear caliper without a built-in parking brake mechanism overhaul is similar.

  1. The first step, even before removing the caliper from the vehicle, is to attempt to open the bleeder valve screw. This fitting is often seized in place in the caliper, especially on high-mileage vehicles or vehicles with aluminum brake calipers and steel bleeder screws. It would be wasted effort to disassemble, clean and overhaul a caliper only to find that it can't be bled because the bleeder screw won't open. It is also very common for a seized bleeder valve screw to snap off when attempts are made to loosen it. Getting the remainder of a seized bleeder screw out of a caliper without damaging the caliper body is very difficult and a job for an automotive machine shop. The fee to attempt to extract a broken bleeder screw will likely exceed the cost of a rebuilt or even new caliper. Try to open the bleeder screw first. If it loosens and brake fluid does flow from the bleeder screw, the caliper may be suitable for an overhaul. The final decision would depend on the condition of the piston bore(s) and he overall condition of the caliper. Remove the caliper using the procedures found in this section.
  2.  
  3. With the caliper removed from the vehicle, place it on a clean work surface. Brake fluid in the caliper will tend to run out onto the work surface, where it can damage painted components. Placing some cardboard or other disposable covering on the work surface may save time at cleanup.
  4.  
  5. Perform a visual inspection. If the caliper has an obvious crack or shows signs of collision damage, it may not be reusable. Check the tapped openings where the mounting bolts thread. In some cases, the threads can be damaged from corrosion or were cross-threaded during previous brake work. Sometimes threaded inserts can be used to save a caliper, but generally, if the caliper body shows signs of abuse, it should be replaced.
  6.  


CAUTION
Do not place your fingers in front of the caliper piston(s) in an attempt to catch or 'protect' the piston(s) when applying compressed air. The piston(s) come out with a surprising amount of force and can serious injure your fingers. In addition, wear eye protection because the brake fluid in the caliper will tend to spray when shop air is applied.

  1. Use clean shop cloths to pad the inside of the brake caliper during piston removal. Use just enough shop air to ease the piston(s) out of the bore(s). If the piston(s) is simply blown out, even with padding provided, it may be damaged. Dual piston calipers must have the pistons removed evenly and at the same rate. If one piston pops out before the other, it will be difficult to built enough pressure to remove the other piston. In the event one piston is seized and will not break free, is may be necessary to block the other piston with a piece of wood or C-clamp until the stuck piston can be freed. When working on dual-piston calipers, some technicians use a block of wood to limit the pistons' travel. Once the technician is assured that both pistons are moving, thinner blocks are used, allowing the pistons to come out evenly until both pistons are out. The piston(s) will come out through the piston dust boot(s).
  2.  
  3. Inspect the pistons for scoring, nicks corrosion, and/or worn or damaged chrome plating. Replace the piston, if any of these conditions are found.
  4.  
  5. Remove the caliper boots, being careful not to scratch the housing bore.
  6.  


WARNING
Do not use a metal tool to remove the piston seals. Metal tools may damage the caliper bores or piston seal grooves.

  1. Remove the piston seals from the groove in the caliper bore, using a small wood or plastic tool. These seals are usually "square profile" O-rings.
  2.  
  3. Inspect the caliper bores, pistons and mounting threads for scoring or excessive wear.
  4.  
  5. Use crocus cloth (an extremely fine abrasive cloth) to polish out light corrosion from the piston and bore. If the crocus cloth cannot remove the corrosion, do not use a more coarse abrasive. The caliper must be replaced.
  6.  
  7. Clean all parts with denatured alcohol and dry with compressed air.
  8.  



Click image to see an enlarged view

Fig. On dual piston calipers, it is important not to completely remove one piston before the other one is freed



Click image to see an enlarged view

Fig. Do NOT put your fingers in front of the pistons when easing them out with compressed air!



Click image to see an enlarged view

Fig. Remove the pistons from the bores



Click image to see an enlarged view

Fig. When removing the caliper boots, be careful not to scratch the bores



Click image to see an enlarged view

Fig. Never use a metal tool to remove the piston seals



Click image to see an enlarged view

Fig. Use a seal driver or a similar tool to seat the dust boots into the caliper housing



Click image to see an enlarged view

Fig. Exploded view of a typical dual piston front disc brake caliper assembly

  1. Lubricate the threads of the bleeder valve with a thin coat of anti-seize compound and install just finger tight. It will be final-tightened after the hydraulic system is bled.
  2.  
  3. Lubricate the new piston seals and bore with clean brake fluid or brake assembly lubricant (a special lubricant found in some brands of brake overhaul parts kits).
  4.  
  5. Install the new seals into the caliper bore grooves, making sure they are not twisted.
  6.  
  7. Lubricate the piston bore.
  8.  
  9. Install the piston(s) and dust boot(s) into the bores of the calipers. Push the piston(s) to the bottom of the bores.
  10.  
  11. Seat the dust boots in the housing using tool J 36349, or equivalent seal installation driver.
  12.  
  13. Install the caliper onto the vehicle, as outlined earlier.
  14.  
  15. Properly bleed the brake system as outlined in this section.
  16.  

Rear
  1. Remove the rear caliper using the procedures found in this section.
  2.  
  3. With the caliper removed from the vehicle, place it on a clean work surface. Brake fluid in the caliper will tend to run out onto the work surface, where it can damage painted components. Placing some cardboard or other disposable covering on the work surface may save time at cleanup.
  4.  
  5. Perform a visual inspection. If the caliper has an obvious crack or shows signs of collision damage, it may not be reusable. Check the tapped openings where the mounting bolts thread. In some cases, the threads can be damaged from corrosion or were cross-threaded during previous brake work. Sometimes threaded inserts can be used to save a caliper, but generally, if the caliper body shows signs of abuse, it should be replaced.
  6.  


CAUTION
Do not place your fingers in front of the caliper piston in an attempt to catch or 'protect' the piston when applying compressed air. The piston come out with a surprising amount of force and can serious injure your fingers. In addition, wear eye protection because the brake fluid in the caliper will tend to spray when shop air is applied.

  1. Use clean shop cloths to pad the inside of the brake caliper during piston removal. Use just enough shop air to ease the piston out of the bore. If the piston is simply blown out, even with padding provided, it may be damaged. The piston will come out through the piston dust boot.
    1. An alternate method for piston removal on these calipers is to use a spanner-type tool (or careful work with pliers) in the slots in the end of the piston to thread the piston out of the caliper.
    2.  

  2.  
  3. Inspect the piston for scoring, nicks corrosion, and/or worn or damaged chrome plating. Replace the piston, if any of these conditions are found.
  4.  
  5. Remove the caliper boot, being careful not to scratch the housing bore. Look for a boot retaining ring. Use a small prying tool to pry up one end of the boot ring. Work the boot ring out of the caliper groove.
  6.  


WARNING
Do not use a metal tool to remove the piston seals. Metal tools may damage the caliper bores or piston seal grooves.

  1. Remove the piston seal from the groove in the caliper bore, using a small wood or plastic tool. These seals are usually "square profile" O-rings.
  2.  
  3. Remove the bleeder valve screw.
  4.  
  5. Remove the lever return spring only if replacement is required. Use a small prytool to disengage the return spring from the parking brake lever. Then unhook the spring from the stopper pin.
  6.  
  7. Remove the caliper mounting bolt (also called a 'slider pin') boots and sleeves from the caliper.
  8.  
  9. Inspect the caliper bores, pistons and mounting threads for scoring or excessive wear.
  10.  
  11. Use crocus cloth (an extremely fine abrasive cloth) to polish out light corrosion from the piston and bore. If the crocus cloth cannot remove the corrosion, do not use a more coarse abrasive. The caliper must be replaced.
  12.  
  13. Clean all parts with denatured alcohol and dry with compressed air. Inspect all parts for damage and replace as necessary.
  14.  



Click image to see an enlarged view

Fig. Exploded view of a rear disc brake caliper equipped with built-in parking brake mechanism



Click image to see an enlarged view

Fig. Using an air gun to coax the piston from the caliper bore



Click image to see an enlarged view

Fig. Removing the piston boot ring



Click image to see an enlarged view

Fig. Removing/installing the parking brake lever return spring



Click image to see an enlarged view

Fig. Cross-sectional view of the piston, showing the proper position of the dust boot on the piston

  1. Lubricate the pin sleeve with silicone grease. Install the pin bolt and pin sleeve to the caliper support. Tighten the bolt to 20 ft. lbs. (27 Nm).
  2.  
  3. Lubricate the sleeve boot with silicone grease to ease installation. Compress the lip sleeve boot and push it all the way through the caliper body until the lip emerges and seats on the inboard face of the caliper ear.
  4.  
  5. Lubricate the sleeve with silicone grease to ease assembly. Push the bolt sleeve in through the lip end of the boot until the boot seats in the sleeve groove at the other end.
  6.  
  7. Install the bolt boot onto the caliper body.
  8.  
  9. Install the pin boot over the pin sleeve (installed on the caliper support).
  10.  
  11. If removed, install a new lever return spring. Position the spring with the hook end around the stopper pin, then pry the other end of the spring over the lever.
  12.  
  13. Lightly lubricate the bleeder valve screw with anti-seize compound and install finger tight. Final tightening will be done after the system is bled.
  14.  
  15. Lubricate a new piston seal with clean brake fluid, then install the seal. Make sure the seal is not twisted.
  16.  
  17. Install the piston boot onto the piston assembly.
  18.  
  19. Lubricate the piston assembly with clean brake fluid, then install the piston and boot into the bore of the caliper body assembly. Start the piston in by hand, then thread it into the bottom of the caliper bore using a suitable spanner-type tool into the slots in the end of the piston assembly.
  20.  
  21. Install the boot ring. Make sure the outside edge of the piston boot is smoothly seated in the counterbore or the caliper body assembly. Work the boot ring into the groove near the open end of the caliper bore, being careful not to pinch the piston boot between the boot ring and the caliper body.
  22.  
  23. After installing the ring, lift the inner edge of the boot next to the piston assembly and press out any trapped air. The boot must lie flat.
  24.  
  25. Install the caliper as outlined earlier in this section. Make sure to properly bleed the brake system.
  26.  

 
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