In case of brake fluid leaks, wheel cylinders must be replaced without fail. Manufacturers do not recommend attempting to perform restorative repairs on these brake mechanism units.
Removal
1. Support the front wheels with wheel chocks. Jack up the rear of the car and place it on supports.
2. Remove the brake drum and shoes (see Removal, inspection and installation of the brake drum).
3. Clean the wheel cylinder and surrounding surfaces from dirt.
4. Remove the cap from the brake master cylinder reservoir, place a piece of polyethylene film underneath it and screw it back into place. Placing the film underneath will seal the cap and prevent fluid from leaking when the flexible brake hose nipple is released.
5. Remove the upper tension spring and move the brake shoes apart, releasing them from the pistons.
6. After thoroughly wiping the nipple, disconnect the hydraulic line from the rear of the wheel cylinder. Use a special open-end wrench with a slotted head to avoid rounding the nipple splines. When disconnecting, do not pull on the metal tube of the brake line to avoid deformation, which can significantly complicate the connection procedure. Immediately plug the open end of the brake line to minimize fluid loss and prevent dirt from entering the hydraulic system.
7. Remove the wheel cylinder mounting bolt.
8. Remove the wheel cylinder from the brake shield and transfer it to a clean workbench.
If there are traces of hydraulic fluid on the friction linings of the brake shoes, the shoes should be replaced and the working surface of the drum should be thoroughly cleaned.
Service
1. Wipe the outside of the cylinder thoroughly.
2. Remove both dust boots from the cylinder.
Design of the wheel cylinder of the rear wheel drum brake mechanism
3. Usually the pistons are freely pushed out of the cylinder under the action of the force developed by the spring. If necessary, plug the end hole of the cylinder with a wooden plug and push the piston out by feeding air into the cylinder through the inlet from the foot pump.
4. Carefully examine the condition of the working surfaces of the cylinder and pistons. If obvious defects are detected, replace the cylinder.
The authors of this Manual recommend replacing the cylinders of both rear wheel brake mechanisms at the same time.
5. If the condition of the components is considered satisfactory, replace the sealing cuffs and dust boots - the corresponding repair kits can always be found in car accessory stores.
6. Lubricate the new piston seals with clean brake fluid and use your finger to insert them into the cylinder, placing the spring in the middle.
7. Dip the pistons in clean brake fluid and fill them into the cylinder.
8. Install new dust boots and check the pistons for free movement.
Installation
1. Make sure the mating surfaces of the cylinder and brake shield are absolutely clean and dry. Spread the shoes, install the cylinder in its regular place and connect the hydraulic line to it - do not tighten the union nut yet.
2. Screw in the mounting bolts and tighten them securely - now the union nut can be finally tightened. Remove the polyethylene placed under the master cylinder reservoir cover.
3. Insert the shoes into the piston grooves and install the upper tension spring in place.
4. Install the brake drum in place (see Removal, inspection and installation of the brake drum).
5. Bleed the brake system (see Bleeding the brake system), - it is enough to bleed only the circuit whose cylinder was removed.
6. Adjust the parking brake drive cable (see Adjusting the parking brake drive). And install the control lever cover in place.
7. Before operating the vehicle, make sure that the brakes are functioning properly.
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