Master cylinder - removal, overhaul and refitting

Braking system / Master cylinder - removal, overhaul and refitting

Note: Before starting work, refer to the warning at the beginning of Section 2 concerning the dangers of hydraulic fluid.

Removal
1 Disconnect the battery negative terminal.

Where necessary, to improve access to the master cylinder, remove the air inlet duct as described in the relevant Part of Chapter 4.

2 Remove the master cylinder reservoir cap, and syphon the hydraulic fluid from the reservoir. Note: Do not syphon the fluid by mouth, as it is poisonous; use a syringe or an old poultry baster. Alternatively, open any convenient bleed screw in the system, and gently pump the brake pedal to expel the fluid through a plastic tube connected to the screw (see Section 2). Disconnect the wiring plug from the brake fluid level sender unit.

3 Wipe clean the area around the brake pipe unions on the side of the master cylinder, and place absorbent rags beneath the pipe unions to catch any surplus fluid. Make a note of the correct fitted position of the unions, then unscrew the union nuts and carefully withdraw the pipes (see illustration). Plug or tape over the pipe ends and master cylinder orifices, to minimise the loss of brake fluid, and to prevent the entry of dirt into the system. Wash off any spilt fluid immediately with cold water.

10.3 Brake master cylinder location front of the servo unit on the

4 Slacken and remove the two nuts and washers securing the master cylinder to the vacuum servo unit, then withdraw the unit from the engine compartment. Remove the Oring from the rear of the master cylinder and discard it.

Overhaul
5 If the master cylinder is faulty, it must be renewed. Repair kits are not available from WV dealers, so the cylinder must be treated as a sealed unit.

6 The only items which can be renewed are the mounting seals for the fluid reservoir; if these show signs of deterioration, pull off the reservoir and remove the old seals. Lubricate the new seals with clean brake fluid, and press them into the master cylinder ports.

Ease the fluid reservoir into position, and push it fully home.

Refitting
7 Remove all traces of dirt from the master cylinder and servo unit mating surfaces, and fit a new O-ring to the groove on the master cylinder body.

8 Fit the master cylinder to the servo unit, ensuring that the servo unit pushrod enters the master cylinder bore centrally. Refit the master cylinder mounting nuts and washers, and tighten them to the specified torque.

9 Wipe clean the brake pipe unions, then refit them to the master cylinder ports and tighten them securely.

10 Refill the master cylinder reservoir with new fluid, and bleed the complete hydraulic system as described in Section 2.