Carefully pull the lower edges of the wheel cylinder boots away from the cylinders to see if the interior of the cylinder is wet with brake fluid. Excessive fluid at this point indicates leakage past the piston cups and a need for wheel cylinder replacement.
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 use 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, then refill and bleed the system.
- Remove the wheel cylinder from the vehicle and place on a clean workbench.
- 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.
- 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.
- Wash the cylinder and metal parts in denatured alcohol or clean brake fluid.
- Allow the parts to air dry or use compressed air. Do not use rags for cleaning, since lint will remain in the cylinder bore.
- Inspect the piston and replace it if it shows scratches.
- Lubricate the cylinder bore and seals using clean brake fluid.
- Position the spring assembly.
- Install the inner seals, then the pistons.
- Insert the new boots into the counterbores by hand. Do not lubricate the boots.
- Install the wheel cylinder.
Removal & Installation
- Raise and safely support the vehicle.
- Remove the rear wheel and tire assembly.
- Remove the brake drum retainers, if equipped.
- Grasp the brake drum and remove.
- If the drum will not slide off with light force, then the brake shoes need to be backed off.
- Remove the brake drum.
- Remove the brake shoes.
- Disconnect the brake line at the wheel cylinder.
- Remove the 2 bolts securing the wheel cylinder to the backing plate and remove the wheel cylinder.
- Reinstall the wheel cylinder to the brake backing plate and install the 2 retaining bolts. Torque the retaining bolts to 84-108 inch. lbs. (10-13 Nm).
- Reconnect the brake line to the wheel cylinder and torque the fitting to 10-18 ft. lbs. (14-24 Nm).
- Lubricate the rear brake shoe contact points on the backing plate with an appropriate grease.
- Install the brake shoes.
- Make sure that the brake drum and brake shoes are clean of any oils or protective coatings.
- Reinstall the brake drum.
- Bleed the brake system of air until a firm pedal is achieved. Top off the brake fluid in the master cylinder.
- Reinstall the wheel and tire assembly.
- Lower the vehicle.
- Pump the brake pedal several times to assure a good pedal.
- Road test the vehicle and check the brake system for proper operation.