Removal
1. Remove the brake master cylinder.
2. Remove the ASR support pump.
3. Check the master cylinder for damage and leaks.
4. Unscrew or disconnect vacuum pipe 8 from vacuum booster 16. Press the brake pedal several times to reduce the pressure in the vacuum booster.
5. Disconnect the A7/7x1, A7/7x2 connector from the BAS control unit or, on models with ESP, disconnect the connector from the solenoid valve switch and the BAS diaphragm displacement sensor on the vacuum booster. On models with BAS and ESP, the BAS control unit is integrated with the ESP control unit.
6. Remove the lower instrument panel cover.
7. Disconnect the brake pedal return spring.
8. Remove the retainer and pin 26.
9. Unscrew nut 23 from bracket 22.
10. Remove the vacuum booster 16.
11. Check gasket 16.
Installation
Installation is carried out in the reverse order of removal.
Examination
1. Press the brake pedal to reduce the pressure in the vacuum booster.
2. Disconnect the tester from the vacuum booster.
3. Attach the pressure gauge 051 to the brake caliper with an adapter.
4. Connect the 060 pedal force sensor to the brake pedal.
5. Start the engine and create a pressure of 0.75-0.80 bar by pressing and releasing the accelerator pedal. If the vacuum achieved is significantly lower than required, or the vacuum decreases immediately, then the sealing ring between the vacuum booster and the master cylinder is damaged or the valve in the vacuum pipe needs to be checked.
6. Apply the required force to the accelerator pedal and read the line pressure.
The hydraulic pressure depending on the pressure on the brake pedal is given in the Specifications.