Vacuum servo unit non-return valve -  removal, testing and refitting

Braking system / Vacuum servo unit non-return valve -  removal, testing and refitting

1 The check valve is in the vacuum hose from the inlet manifold to the brake servo (see illustration). If the valve is to be renewed, the complete hose/valve assembly should be replaced.

13.1 Vacuum servo unit non-return valve

Removal
2 Ease the vacuum hose out of the servo unit, taking care not to displace the grommet.

3 Note the routing of the hose, then slacken the clip and disconnect the opposite end of the hose assembly from the manifold and remove it from the car.

Testing
4 Examine the check valve and vacuum hose for signs of damage, and renew if necessary.

5 The valve may be tested by blowing through it in both directions, air should flow through the valve in one direction only; when blown through from the servo unit end of the valve. Renew the valve if this is not the case.

6 Examine the servo unit rubber sealing grommet for signs of damage or deterioration, and renew as necessary.

Refitting
7 Ensure that the sealing grommet is correctly fitted to the servo unit.

8 Ease the hose union into position in the servo, taking great care not to displace or damage the grommet.

9 Ensure that the hose is correctly routed, and connect it to the inlet manifold, tightening its retaining clip securely.

10 On completion, start the engine and check the check valve to servo unit connection for signs of air leaks.