Brake Master Cylinder: Service and Repair

REMOVAL





1. Remove the fluid level warning device connector.
2. Disconnect the brake lines from the master cylinder, and plug the opening ports.

CAUTION: Do not allow brake fluid to remain on a painted surface. Wash it off immediately.

3. Remove the master cylinder mounting nuts. Disconnect the proportioning valve mounting bracket, then lift out the master cylinder.
4. Remove the reservoir cap and drain the brake fluid into a suitable container.
5. Remove the reservoir from the master cylinder.

NOTE: If necessary, support the master cylinder in a vise at its flange not at its bore.





6. While depressing the piston, remove the snap ring.





7. Remove the primary and secondary pistons from the master cylinder, and then push the secondary piston through the master cylinder by using a screw driver and then remove the secondary piston stopper pin by slightly tilting the master cylinder.

NOTE:
1. Be careful not to damage the cylinder bore.
2. Do not disassemble the primary and secondary piston assemblies.

INSPECTION
1. Check the master cylinder bore for rust or scoring.
2. Check the primary and secondary pistons for rust, scoring, wear, damage or deterioration.
3. Check the primary and secondary piston springs for deterioration.

REASSEMBLY





1. Apply the specified brake fluid to the inner surface of the master cylinder body and to the outside of the secondary and primary pistons.
Recommended brake fluid: DOT 3 or equivalent
2. Installation is the reverse of the removal procedure.





3. Depress the primary piston and install the snap ring in the cylinder bore groove as illustrated.
4. Install the reservoir cap on the reservoir.
5. Lubricate the two grommets (both, inside and outside) with genuine brake fluid and then insert them into the master cylinder body.

NOTE: Whenever the reservoir is replaced, the grommets must also be replaced.





6. Press the reservoir into the master cylinder body with the fluid level indicator socket facing inboard. The reservoir should snap in place indicating that it is secure as illustrated.
7. Connect the fluid level warning connector in the socket on the reservoir.





8. Install the master cylinder on the brake booster with two nuts.
Nut: 8 - 12 Nm (80 - 120 kg.cm, 6 - 9 ft. lbs.)
9. Connect two brake tubes and fluid level warning connector.
Brake tube flare nut: 13 - 17 Nm (130 - 170 kg.cm, 9 - 12 ft. lbs.)
10. Fill the master cylinder reservoir with brake fluid and bleed the system.