GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Manual

Wheel Cylinders

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REMOVAL & INSTALLATION



See Figures 1, 2, 3 and 4

  1. Raise and support the rear of the vehicle safely using jackstands.
  2.  
  3. Remove the tire and wheel assembly.
  4.  
  5. Matchmark and remove the brake drum for access to the wheel cylinder assembly.
  6.  

In most cases, the wheel cylinders may be removed from the backing plate without completely removing the brake shoes and related components, however completely removing the shoes will make the operation MUCH easier. If the shoes are not completely removed, some of the upper springs must be removed in order to allow the shoes to spread and provide the necessary clearance for wheel cylinder removal.

  1. Remove the brake shoes or disconnect them sufficiently for wheel cylinder clearance.
  2.  



Click image to see an enlarged view

Fig. Fig. 1: Exploded view of a common wheel cylinder mounting-round retainer type

  1. Clean away all dirt, crud and foreign material from around wheel cylinder. It is important that dirt be kept away from the brake line when the cylinder is disconnected.
  2.  
  3. Disconnect the inlet tube line from the back of the wheel cylinder. Immediately plug or cap the line to prevent system contamination or excessive fluid loss.
  4.  

Wheel cylinders are retained to the rear of the brake backing plate by two types of fasteners. One type uses a round retainer with locking clips while the other simply uses two bolts threaded into the wheel cylinder body.

  1. To remove the round retainer type cylinders, insert two awls or pins into the access slots between the wheel cylinder pilot and the retainer locking tabs. Bend both tabs away simultaneously. The wheel cylinder can be removed, as the retainer is released.
  2.  
  3. To remove the bolted wheel cylinders, loosen and remove the bolts from the back side of the backing plate, then remove the wheel cylinder assembly.
  4.  

To install:
  1. For round retainer type wheel cylinders, position the cylinder and hold it in place with a wooden block between the cylinder and the axle flange. Install the new retainer clip, using a 1 1 / 8 in. 12-point socket and socket extension (to help preserve your fingers). The socket is used to assure that the retainer seats evenly.
  2.  
  3. For bolt type wheel cylinders, position the cylinder, then install the retaining bolts and tighten to 115 inch lbs. (13 Nm).
  4.  
  5. Remove the cap or plug, then connect and secure the hydraulic inlet line.
  6.  
  7. Assemble the remaining brake components which were removed.
  8.  
  9. Align and install the brake drum, then install the tire and wheel assembly.
  10.  
  11. Bleed the wheel cylinder and adjust the brakes (if necessary).
  12.  
  13. Remove the jackstands and carefully lower the vehicle.
  14.  



Click image to see an enlarged view

Fig. Fig. 2: Two awls may be used to bend the retainer stubs, releasing the wheel cylinder



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Fig. Fig. 3: Once the cylinder is free of the backing plate, it can be removed from the vehicle



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Fig. Fig. 4: Upon installation of round retainer type cylinders, a socket should be used to seat the retainer

OVERHAUL



See Figures 5, 6 and 7



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Fig. Fig. 5: Carefully remove the old boots from the wheel cylinder



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Fig. Fig. 6: A small amount of compressed air may be used to free the inner components



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Fig. Fig. 7: Exploded view of the wheel cylinder assembly

Wheel cylinder overhaul kits may be available, but often at little or no savings over a reconditioned wheel cylinder. It often makes sense with these components to substitute a new or reconditioned part instead of attempting an overhaul.

If no replacement is available, or you would prefer to overhaul your wheel cylinders, the following procedure may be used. When rebuilding and installing wheel cylinders, avoid getting any contaminants into the system. Always install clean, new, high-quality brake fluid. If dirty or improper fluid has been used, it will be necessary to drain the entire system, flush the system with proper brake fluid, replace all rubber components, refill, and bleed the system.

  1. Remove the wheel cylinder from the vehicle.
  2.  
  3. First remove and discard the old rubber boots, then withdraw the pistons. Piston cylinders are equipped with seals and a spring assembly, all located behind the pistons in the cylinder bore.
  4.  
  5. Remove the remaining inner components seals and spring assembly. Compressed air may be useful in removing these components. If no compressed air is available, be VERY careful not to score the wheel cylinder bore when removing parts from it. Discard all components for which replacements were supplied in the rebuild kit.
  6.  
  7. Wash the cylinder and metal parts in denatured alcohol or clean brake fluid.
  8.  


CAUTION
Never use a mineral-based solvent such as gasoline, kerosene, or paint thinner for cleaning purposes. These solvents will swell rubber components and quickly deteriorate them.

  1. Allow the parts to air dry or use compressed air. Do not use rags for cleaning since lint will remain in the cylinder bore.
  2.  
  3. Inspect the piston and replace it if it shows scratches.
  4.  
  5. Lubricate the cylinder bore and seals using clean brake fluid.
  6.  
  7. Position the spring assembly.
  8.  
  9. Install the inner seals then the pistons.
  10.  
  11. Insert the new boots into the counterbores by hand. Do not lubricate the boots.
  12.  
  13. Install the wheel cylinder to the vehicle.
  14.  

 
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