If wheel cylinders are leaking or seized, they should be replaced. The units are inexpensive enough to often make replacement a better choice than repair. Even if the pistons and seals can be replaced, the internal bore can rarely be restored to perfect condition. A faulty repair can reduce braking effort on the wheel or cause a leak which soaks the brake shoes in fluid.
When inspecting the cylinders on the car, the rubber boots must be lifted carefully and the inner area checked for leaks. A very slight moistness usually coated with dust is normal, but any accumulation of fluid is evidence of a leak and must be dealt with immediately.
REMOVAL & INSTALLATION
We recommend replacement of the wheel cylinders in axle sets for added safety and reliability
- Remove the brake drums and shoes as detailed earlier in this section.
- Working from behind the backing plate, disconnect the hydraulic line from the wheel cylinder.
- Unfasten the screws retaining the wheel cylinder and withdraw the cylinder.
- Installation is performed in the reverse order of removal.
However, once the hydraulic line has been disconnected from the wheel cylinder, the union must be replaced on early models. This step is not necessary on newer models
Replace the seat (only if necessary) in the following manner:
- Use a screw extractor with a diameter of 0.1 inch (2.5mm) and having reverse threads, to remove the union seat from the wheel cylinder.
- Drive in the new union seat with a 5 / 16 inch bar, used as a drift. Remember to bleed the brake system after completing wheel cylinder, brake shoe and drum installation.
See Figures 1 through 5
It is not necessary to remove the wheel cylinder from the backing plate if it is only to be inspected or rebuilt
- Remove the brake drum and shoes. Remove the wheel cylinder only if it is going to be replaced.
- Remove the rubber boots from either end of the wheel cylinder.
- Withdraw the piston and cup assemblies.
- Take the compression spring out of the wheel cylinder body.
- Remove the bleeder plug (and ball), if necessary. Check all components for wear or damage. Inspect the bore for signs of wear, scoring and/or scuffing. If in doubt, replace or hone the wheel cylinder (with a special hone). The limit for honing a cylinder is 0.005 inch (0.1mm) oversize. Wash all the residue from the cylinder bore with clean brake fluid and blow dry.
- Soak all components in clean brake fluid, or coat them with the rubber grease supplied in the wheel cylinder rebuilding kit.
- Install the spring, cups (recesses toward the center), and pistons in the cylinder body, in that order.
- Insert the boots over the ends of the cylinder.
- Install the bleeder plug (and ball), if removed.
- Assemble the brake shoes and install the drum.