Caution: Do not disturb or remove the screw which retains the primary spring to the secondary piston. This screw has been set to a predetermined height, and the performance of the master cylinder will be adversely affected if this setting is changed. An improperly adjusted screw may result in poor brake performance and possible personal injury.

Important: The reservoir cap and the diaphragm may be inspected and serviced without removing the master cylinder from the vehicle.

1. Remove the ABS hydraulic modulator and master cylinder assembly. Refer to Brake Modulator/Master Cylinder Assembly Replacement in Antilock Brake System.
2. Wipe the reservoir cap clean.
3. Remove the reservoir cap and the diaphragm.
4. Replace the reservoir cap and the diaphragm if the following damage is evident:

•

Cuts

•

Cracks

•

Nicks

•	Deformation

5. Remove the master cylinder reservoir. Refer to Master Cylinder Reservoir Replacement .
6. Remove the proportioning valves. Refer to Proportioning Valve Replacement .



7. Remove the retainer (2) while depressing the primary piston (3). Do not damage the piston, the bore or the retainer groove.
8. Apply low pressure, non-lubricated, compressed air into the upper outlet port at the blind end of the bore while the other outlet ports are plugged. Do this in order to remove the following parts:

8.1.	Primary piston (3)

8.2.	Secondary piston (5)

8.3.	Spring (8)

8.4.	Spring retainer (7)

9. Remove the seals (4 and 6) and the spring retainer (7) from the secondary piston (5).
10. Inspect the master cylinder (1) for scoring or corrosion. Replace the master cylinder (1) if damage exists. Do not use abrasives in the bore.
11. Clean all of the parts in clean, denatured alcohol.
12. Dry the parts. Use non-lubricated, compressed air.



13. Install lubricated seals (4 and 6) and the spring retainer (7) onto the secondary piston (5).
14. Install the spring (8) and the secondary piston (5) into the cylinder bore. Lubricate the parts. Use clean brake fluid in order to ease assembly.
15. Install the lubricated primary piston (3) into the cylinder bore.
16. While depressing the primary position (3), install the retainer (2).
17. Install the proportioning valves. Refer to Proportioning Valve Replacement .
18. Install the master cylinder reservoir. Refer to Master Cylinder Reservoir Replacement .
19. Insert the diaphragm into the reservoir cap.
20. Install the cap on the reservoir.
21. Install the ABS hydraulic modulator and master cylinder assembly. Refer to Brake Modulator/Master Cylinder Assembly Replacement in Antilock Brake System.