Wheel Cylinders

Wheel cylinders should not be disassembled unless they are leaking. Carefully pull lower edges of wheel cylinder boots away from cylinders to see if the interior of the cylinder is wet with brake fluid. Excessive fluid at this point indicates leakage past piston cups and a need for wheel cylinder overhaul.

NOTE: A slight amount of fluid is nearly always present and acts as a lubricant for the piston. It is not necessary to remove the brake cylinder from the backing plate to disassemble, inspect, hone and overhaul the cylinder. Removal is necessary only if the cylinder is damaged or scored beyond service.

Disassembly

1. Remove the boots, pistons, cups, and return spring and expander assembly from the cylinder bore.

2. Remove the bleeder screw from the cylinder.

3. Discard all rubber parts, and wash all other parts in clean denatured alcohol.

4. Inspect pistons for scratches, scoring or other visible damage. Replace if necessary. Always discard the rubber cups and dust boots.

5. Inspect the cylinder bore for score marks or rust. If either condition is present, the cylinder bore must be honed. However, the cylinder should not be honed more than 0.08mm (0.003 inch) beyond its original diameter.

6. Wash the cylinder with clean, denatured alcohol after honing, and dry it with compressed air.

7. Check the bleeder hole to ensure it is open.

Assembly

Use all parts in the wheel cylinder service kit.

1. Apply a light coating of heavy-duty brake fluid to all internal parts.

2. Thread the bleeder screw into the cylinder.

3. Insert the return spring and expander assembly, cups, and pistons into their respective positions in the cylinder bore. Place a boot over each end of the cylinder.