Wheel Cylinder: Service and Repair

REMOVAL
1. Remove wheel and tire assembly.
2. Remove brake drum.
3. Disconnect wheel cylinder brake line.
4. Remove brake shoe return springs and move shoes out of engagement with cylinder push rods.
5. Remove cylinder attaching bolts and remove cylinder from support plate.

DISASSEMBLY





1. Remove push rods and boots.
2. Press pistons, cups and spring and expander out of cylinder bore.
3. Remove bleed screw.

CLEANING
Clean the cylinder and pistons with clean brake fluid or brake cleaner only. Do not use any other cleaning agents.
Dry the cylinder and pistons with compressed air. Do not use rags or shop towels to dry the cylinder components. Lint from cloth material will adhere to the cylinder bores and pistons.

INSPECTION
Inspect the cylinder bore. Light discoloration and dark stains in the bore are normal and will not impair cylinder operation.

The cylinder bore can be lightly polished but only with crocus cloth. Replace the cylinder if the bore is scored, pitted or heavily corroded. Honing the bore to restore the surface is not recommended.

Inspect the cylinder pistons. The piston surfaces should be smooth and free of scratches, scoring and corrosion. Replace the pistons if worn, scored, or corroded. Do attempt to restore the surface by sanding or polishing.

Discard the old piston cups and the spring and expander. These parts are not reusable. The original dust boots may be reused but only if they are in good condition.

ASSEMBLY
1. Lubricate wheel cylinder bore, pistons, piston cups and spring and expander with clean brake fluid.
2. Install first piston in cylinder bore. Then install first cup in bore and against piston. Be sure lip of piston cup is facing inward (toward spring and expander) and flat side is against piston.
3. Install spring and expander followed by remaining piston cup and piston.
4. Install boots on each end of cylinder and insert push rods in boots.
5. Install cylinder bleed screw.

INSTALLATION
1. Apply bead of silicone sealer around cylinder mounting surface of support plate.
2. Install cylinder mounting bolts and tighten to 20 Nm (15 ft. lbs.).
3. Connect brake line to cylinder.
4. Install brake shoe return spring.
5. Install brake drum.
6. Install wheel and tire assembly.
7. Bleed base brake system.