Before deciding to rebuild a wheel cylinder, make sure parts are available. It's sometimes more practical to simply replace the old wheel cylinder with a new or rebuilt unit instead of rebuilding it. Raise the rear of the vehicle and support it securely on jackstands, then block the front wheels. Remove the rear wheels. Remove the rear hub/drum and the brake shoes. Disconnect the
Brake Line (tube) from the back of the wheel cylinder and plug it. Unbolt the wheel cylinder and remove it from the backing plate. Clean the backing plate and wheel cylinder mating surfaces. Remove the bleeder screw and check to make sure it is not obstructed. Carefully pry the boots from the wheel cylinder and remove them. Push in on one piston and force out the opposite piston, cups and spring with the cup expanders from the bore. Clean the wheel cylinder, pistons and spring with clean brake fluid, denatured alcohol or brake system cleaner and dry them with compressed air. Check the cylinder bore and pistons for score marks and corrosion (pitting). Slight imperfections in the bore can be removed with fine crocus cloth (use a circular motion). Black stains on the cylinder walls are caused by the cups and will not impair brake operation. If the pistons or wheel cylinder bore are badly scored or pitted, replace the wheel cylinder. Lubricate the components with clean brake fluid or brake assembly lubricant prior to installation. With the cylinder bore coated with clean brake fluid or brake assembly lube, install the spring and cup expanders. Install the cups in each end of the cylinder. Make sure the open ends of the cups are facing each other. Engage the boot on the piston and slide the assembly into the bore. Carefully press the boot over the cylinder end until it is seated. Repeat the procedure for the remaining boot and piston. Install the bleeder screw. Apply ATV-type sealant to the wheel cylinder mating surface of the backing plate. To install the wheel cylinder, hold it in position, install the mounting bolts and tighten them. Unplug the brake line, insert it into the wheel cylinder fitting and carefully thread the flare nut into place. Once the nut is properly started, tighten it securely with a wrench. Install the brake shoes and the hub/drum. Bleed the brakes. Install the wheels and lower the vehicle. Check the brake operation very carefully before placing the vehicle into normal service.