Vacuum Brake Booster: Testing and Inspection

Special tool(s): 999 5843, vacuum pump

[LG1]
- Check that ignition is switched off.





- Remove vacuum hose from non-return valve on power brake booster.

[LG2]





- Connect a vacuum pump (special tool 999 5843) to non- return valve using hose, adapter and clips.
- Create a powerful vacuum in the power brake booster using the pump and note gauge reading.

[LG3]
- If vacuum then falls, this means there is a leak.
- Remove vacuum pump from power brake booster.
- Depress brake pedal a few times so no vacuum remains in the power brake booster.
- Check non-return valve and seal. Replace if damaged.
- Remove pedal sensor connector.
- Open circlip and remove sensor from power brake booster.
- Check 0-ring condition and adhesion. Replace if necessary

[LG4]

Note: If neither the seals nor the non-return valve are damaged, this means there is a leak in the power brake booster itself, and this must therefore be replaced. Replacement procedure as per LD or LE. Service and Repair

Replace power brake booster as per LD. Then continue as below.

[LG5]
- Install non-return valve hose on power brake booster.