Vacuum Brake Booster: Service and Repair

NOTE: Other than replacing the filter, non-return valve and grommet, the servo is not a serviceable component, in the event of failure or damage fit a new unit.

REMOVE
1. Disconnect the battery negative terminal.
2. Disconnect the electrical plug to the low fluid level switch.
3. Thoroughly clean the immediate area around all master cylinder outlet ports. Remove each of the brake pipes from the master cylinder in turn, sealing each pipe and outlet port as they are disconnected with suitable plugs, to prevent ingress of foreign matter and excessive fluid loss.
4. Disconnect the vacuum supply hose to the servo.
5. From inside the vehicle remove the lower dash panel to gain access to the spring clip securing the servo push rod to the brake pedal assembly.

Servo Assembly - Removing:

6. Release the spring clip and remove the clevis pin securing the servo push rod to the brake pedal.
7. Remove the two nuts and plain washers securing the servo to the bulkhead pedal box.
8. From within the engine compartment withdraw the servo and master cylinder assembly.
9. Remove the cap from the reservoir and drain the brake fluid into a suitable container. If the master cylinder - assembly can be kept horizontal it will not be necessary to drain the fluid.

CAUTION: Do not use brake fluid previously drained or bled from the system. Carefully dispose of unwanted fluid, if stored in a sealed container, ensure that the container is marked USED BRAKE FLUID.

Brake Servo:

10. Detach the spacer from the pedal box mounting face of the servo, it is important that the spacer is fitted to the mounting face of the new servo to ensure that stringent pedal to servo operating dimensions are maintained.
11. If a new servo is being fitted it will be necessary to remove the master cylinder from the existing servo and refitted to the new unit.

REFIT
1. Fit the spacer previously removed from the old servo, to the new servo.
2. Fit the servo to the pedal box assembly.
3. From inside the vehicle lightly grease the brake pedal around the area that the servo push rod pivots.
4. Fit the push rod to the brake pedal and secure in position with the clevis pin and clip.
5. Fit the plain washers and secure the servo with the two nuts. Tighten the nuts to 22-25 Nm (16-19 ft lb).
6. Refit the lower dash panel.
7. Fit the master cylinder to the servo, refit the plain and spring washers and secure the master cylinder to the servo with the two nuts. Tighten the nuts to 21-29 Nm (15-22 ft lb).
8. Remove the sealing plugs, fitted to the master cylinder outlet ports during the removal procedure and refit the brake pipes to their respective ports. Tighten the brake pipes to 9-11 Nm (7-8 ft lb).
9. Refit the vacuum supply hose.
10. Fill the master cylinder to between the MAX and MIN level markings with the correct grade of brake fluid.
11. Bleed the brake systems.