Thursday, June 2, 2011

how to change the brake shoes on Chevy Lumina?

CAUTION
Older brake pads or shoes 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 the brake surfaces, use a commercially available brake cleaning fluid.

When servicing drum brakes, only disassemble and assemble one side at a time, leaving the remaining side intact for reference.

INSPECTION



After removing the brake drum, inspect the brake shoes. If the lining is worn down to within 1 / 32 in. (0.8mm) above the rivet, the shoes must be replaced.

This figure may disagree with your state's automobile inspection laws. If the brake lining is soaked with brake fluid or grease, it must be replaced. If this is the case, the brake drum should be sanded with crocus cloth to remove all traces of brake fluid, and the wheel cylinders should be rebuilt. Clean all grit from the friction surface of the drum before replacing it.

If the lining is chipped, cracked or otherwise damaged, it must be replaced with a new lining.

Always replace the brake linings in sets of two on both ends of the axle. Never replace just one shoe or both shoes on one side.

Check the condition of the shoes, retracting springs and hold-down springs for signs of overheating. If the shoes or springs have a slight blue color, this indicates overheating, then replacement of the shoes and springs is recommended. The wheel cylinders should be rebuilt as a precaution against future problems.

REMOVAL AND INSTALLATION



To remove the brake shoes, you will need a suitable brake shoe spanner and spring removal tool. This tool will make removing the actuator spring much easier.

  1. Raise and safely support the vehicle.
  2. Remove the wheel and tire assembly.
  3. Remove the brake drum.

See Figures 1 and 2

Click image to see an enlarged view

Fig. Fig. 1: View of the rear brakes with the drum removed



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Fig. Fig. 2: Diagram of brakes, with the rear hub removed.

  1. Remove the actuator spring, as follows:
    1. Use a suitable brake shoe spanner/spring removal tool to pry the loop end of the spring from the adjuster actuator,.


The actuator spring can also be called the adjuster spring.

    1. Disconnect the spring from the web of the parking brake shoe.


See Figures 3, 4 and 5

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Fig. Fig. 3: Use the brake shoe spanner/spring removal tool to remove the actuator spring



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Fig. Fig. 4: Once it is disengaged, remove the actuator spring from the actuator



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Fig. Fig. 5: View of the adjuster actuator assembly

  1. Lift the end of the retractor spring from the adjuster shoe and lining assembly

The retractor spring is also commonly referred to as the return spring.

  1. Insert the hook end of the brake spring removal tool between the retractor spring and the adjuster shoe web.

See Figure 6

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Fig. Fig. 6: Disengaging the retractor, or return, spring

  1. Pry or twist the spring removal tool to lift the end of the spring out of the shoe web hole.
  2. Pry the end of the retractor spring toward the axle with the flat edge of the tool until lit snaps down off the shoe web onto the backing plate.
  3. Remove the adjuster shoe and lining assembly, the adjuster actuator, and the adjusting screw assembly.

See Figure 7

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Fig. Fig. 7: View of the brake adjuster assembly

  1. Do not remove the parking brake cable from the parking brake lever unless the parking brake lever is to be replaced.
  2. Lift the end of the retractor spring from the parking brake shoe and lining assembly.
  3. Insert the hook end of the spring remover between the retractor spring and the park brake shoe web.
  4. Pry the end of the retractor spring toward the axle with the flat edge of the tool until lit snaps down off the shoe web onto the backing plate.
  5. Remove the park brake shoe and lining assemblies.
  6. Remove the retractor spring from the anchor plate.

If only shoe and lining are being serviced, it is not necessary to remove the retractor spring.

See Figure 8

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Fig. Fig. 8: This is a diagram of the brake parts, removed from the backing plate.

To install:

Before reinstalling the adjusting screw assembly, disassemble the adjusting screw and thoroughly clean and lubricate the adjusting screw threads and adjuster socket inside diameter with a brake lubricant.

  1. Apply brake lubricant to the six raised shoe pads on the backing plate assembly
  2. If the retractor spring was removed, reinstall it, hooking the center spring section under the tab on the anchor.
  3. Install the shoe and lining assembly as follows:
    1. Position shoe and lining on the backing plate.
    2. Using the brake shoe spanner/spring removal tool, pull the end of the retractor spring up to rest on the web of the brake shoe.
    3. Use the spring removal tool to pull the end of the retractor spring over until it snaps into the slot in the brake shoe.


See Figures 9 and 10

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Fig. Fig. 9: Pulling the spring end onto the shoe web



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Fig. Fig. 10: Pull the spring end into the shoe slot

  1. Install the parking brake lever to the parking brake shoe and linings assemblies.
  2. Reconnect the parking brake cable to the parking brake lever, if it was disconnected.
  3. Install the adjusting screw assembly and adjuster shoe lining assembly.
    1. Engage the pivot nut with the web of the parking brake shoe and lining and parking brake lever.
    2. Position the adjuster shoe and lining so the shoe web engages the deep slot in the adjuster socket.

  4. Install the retractor spring into the adjuster shoe and lining assembly, as follows:
    1. Using the brake spring removal tool, pull the end of the retractor spring up to rest on the web of the brake shoe.
    2. Use the brake spring removal tool to pull the end of the retractor spring over until it snaps into the slot in the brake shoe.

  5. Install the adjuster actuator, lubricate the tab, and pivot point on the adjuster actuator with brake lubricant.
    1. Using the brake spanner/spring removal tool, spread the brake shoes while working the adjuster actuator into position.

  6. Install the actuator spring.
    1. Engage the U-shaped end of the spring into the hole in the web of the park brake shoe.
    2. Use the brake spring tool to stretch the spring and engage the loop end over the tab on the adjuster actuator.


Check the arm of the adjuster actuator; it should be resting freely on the star wheel teeth of adjuster screw, not trapped under the teeth in a downward angle.

  1. Pull apart the upper ends of the shoe and lining assemblies, and watch for the proper rotation of the star wheel.

See Figure 11

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Fig. Fig. 11: View of the brake shoes assembled and related components

  1. Install the brake drum in position.
  2. Install the wheel and tire assemblies.
  3. Cheek the adjustment of the brakes by turning the star wheel so that the shoe and lining diameter is 0.050 in. (1.3mm) less than inside drum diameter. The brakes should drag just slightly. If the wheel will not turn, loosen the adjuster slightly.

ADJUSTMENTS



The drum brakes self-adjust anytime the brakes are applied, with no vehicle motion required. This system works well and no manual adjustment is usually necessary. Adjustment will be required when new brake shoes are installed. The following procedure is with the brake drum removed.

  1. Raise and support the car safely.
  2. Mark the relation of wheel to studs, so you install it in the same location.
  3. Remove the wheel and tire assembly.
  4. Remove the brake drum.
  5. Make certain the parking brake is off and the brake shoes are sitting against the stops. If not readjust the parking brake, as outlined later in this section.
  6. Measure the drum inside diameter using a suitable drum-to-brake shoe clearance gauge.

See Figure 12

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Fig. Fig. 12: Use a suitable gauge to measure the drum and shoes for adjustment

  1. Turning the adjuster nut (star wheel on the adjuster), adjust the shoe and lining diameter to be 0.050 in. (1.27mm) less than the inside drum diameter for each rear wheel. Go slowly and don't overtighten or force the drum on. It's very difficult to remove the drum on an overadjusted system.

See Figure 13

Click image to see an enlarged view

Fig. Fig. 13: Location of the drum brake adjuster screw assembly

  1. If you've over-adjusted or the drum is hard to remove; remove the access hole plug from the backing plate. Insert a flat tool though the hole and press in to push the park brake lever off its stop. This allows the lining to retract. You must not remove the drum and reassemble the brakes. Don't pry on the backing plate. If necessary, insert a punch through the hole at the bottom of the splash shield and tap gently to loosen drum.
  2. After adjustment, install the drum and the tire and wheel assembly.
  3. Perform the adjustment procedure at the other rear wheel and tire assembly.
  4. Carefully lower the vehicle, then tighten the lug nuts to 100 ft. lbs. (136 Nm).
  5. Apply and release the brakes about 30-35 times with normal pedal force, pausing about one second between pedal applications.


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