Brake Master Cylinder Repair

Disassemble

Removal of the master cylinder seal. A. SCREWDRIVER.

9. SEAL

Pushing the pistons into the master cylinder

A. WOODEN OR PLASTIC PUSH ROD.

B. 3 MM WELDING WIRE.

5. MASTER CYLINDER BODY

Removal of the retaining ring. A. SCREWDRIVER.

B. 3 MM WELDING WIRE.

8. RETAINING RING

Removal of the rear piston from the master cylinder. A. COMPRESSED AIR HOSE NOZZLE.

6. REAR PISTON ASSEMBLY

PROCEDURE.

1. Remove the master cylinder assembly.

2. Secure the master cylinder in a vise and remove the reservoir.

2..

3. Remove seal 9 from the cylinder bore.

4. Push pistons 6 and 7 approximately 10 mm into the cylinder using a wooden or plastic push rod of suitable size. To hold the pistons in the pushed-in position, insert a 3 mm

welding wire into the cylinder compensating port.

(See illustration: Pushing the pistons into the master cylinder.)

5. Using a screwdriver, remove retaining ring 8 from the cylinder groove.

Warning.

Protect the pistons and the inner walls of the master cylinder from mechanical

damage.

Do not reuse the retaining ring.

6. Push pistons 6 and 7 into the cylinder using a wooden or plastic push rod of suitable size, and remove the wire.

7. Remove front piston 7 from the cylinder bore. To do so, tap the end of the cylinder

against a wooden block.

8. Remove rear piston 6 from the cylinder bore.

9. Blow out the ports using compressed air.

10. Wash all parts in fresh brake fluid or alcohol. Dry the parts with a stream of compressed air.

11. Inspect the inner surface of the cylinder for scratches and signs of

corrosion. If defects are found, replace the master cylinder.

Warning.

Do not use abrasive tools, emery cloth, or products containing abrasive particles to

treat the master cylinder bore.

Do not reuse the rubber seals or the retaining ring.

8..

Assembly.

PROCEDURE.

1. Lubricate the inner surface of the master cylinder with fresh brake fluid.

2. Secure master cylinder body 5 in a vise so that the reservoir connection

ports face upward.

3. Carefully insert rear piston assembly 6 into the cylinder bore and push it fully into the cylinder. Use a wooden or plastic push rod to advance the piston.

4. Install front piston 7.

7..

5. Press pistons 7 and 6 into the cylinder and insert welding wire into the cylinder compensating port to hold the pistons in place during installation of the retaining ring.

8..

6. Install new retaining ring 8 into the groove in the cylinder bore.

Warning.

Work carefully to avoid damaging the inner surface of the master

cylinder.

7. Press pistons 7 and 6 into the cylinder using a push rod, and remove the welding wire

from the compensating port.

8. Check that the pistons move freely and smoothly in the master cylinder.

9. Lubricate seal 9 with fresh brake fluid and insert it fully into the cylinder bore until it contacts

the retaining ring. The open side of seal 9 must face outward.

10. Install the master cylinder assembly in place.

11. Bleed air from the hydraulic system.