Removal
1. Slacken the retaining clip (where fitted) and disconnect the vacuum hose from the servo unit check valve.
2. Withdraw the valve from its rubber sealing grommet, using a pulling and twisting motion. Remove the grommet from the servo.
Testing
3. Examine the check valve for signs of damage and renew if necessary. 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.
4. Examine the rubber sealing grommet and flexible vacuum hose for signs of damage or deterioration and renew as necessary.
Refitting
5. Fit the sealing grommet into position in the servo unit.
6. Carefully ease the check valve into position, taking great care not to displace or damage the grommet. Reconnect the vacuum hose to the valve and, where necessary, securely tighten its retaining clip.
7. On completion, start the engine and check the check valve-to-servo unit connection for signs of air leaks. Test the servo operation as described at the start of Section 16.