Since the travel of the pistons in the wheel cylinder changes when new brake shoes are installed, it is possible for previously good wheel cylinders to start leaking after new brakes are installed. Therefore, to save yourself the expense of having to replace new brakes that become saturated with brake fluid and the aggravation of having to take everything apart again, it is strongly recommended that wheel cylinders be rebuilt every time new brake shoes are installed. This is especially true for cars with high mileage.
- Remove the brakes.
- Place a bucket or old newspapers under the brake backing plate to catch the brake fluid that will run out of the wheel cylinder.
- Remove the boots from the ends of the wheel cylinders.
- Push one piston toward the center of the cylinder to force the opposite piston and cup out the other end of the cylinder. Reach into the open end of the cylinder and push the spring, cup and piston out of the cylinder.
- Remove the bleeder screw from the rear of the cylinder, on the back of the backing plate.
- Inspect the inside of the wheel cylinder. If it is scored in any way, the cylinder must be honed with a wheel cylinder hone or fine emery paper, and finished with crocus cloth if emery paper is used. If the inside of the cylinder is excessively worn, the cylinder will have to be replaced, as only 0.003 in. of material can be removed from the cylinder walls. When honing or cleaning wheel cylinders, keep a small amount of brake fluid in the cylinder to serve as a lubricant.
- Clean any foreign matter from the pistons. The sides of the pistons must be smooth for the wheel cylinders to operate properly.
- Clean the cylinder bore with alcohol and a lint-free rag. Pull the rag through the bore several times to remove all foreign matter and dry the cylinder.
- Install the bleeder screw and the return spring in the cylinder.
- Coat new cylinder cups with new brake fluid and install them in the cylinder. Make sure they are square in the bore or they will leak.
- Install the pistons in the cylinder after coating them with new brake fluid.
- Coat the insides of the boots with new brake fluid and install them on the cylinder. Install the brakes.
REMOVAL & INSTALLATION
See Figures 1 through 5