Power Brake System Function Test

CHECKING BRAKE BOOSTING SYSTEM
- Discharge the hydraulic reservoir by operating the brake pedal about 20 times with the engine stopped and a force equal to full stop braking.
- Pull off wires and unscrew hydraulic switch.
- Mount Special Tools 34 3 160 and 32 4 005.

Installation Note: Tightening torque = 18 Nm (13 ft lb).





- Connect pressure tester 32 4 000 or alternatively 54 3 100 on Special Tools 34 31 60 and 32 4 005.




- Close both valves (1 and 2).

Checking Power Flow Regulator and Brake Booster for Leaks
- Start engine and observe the pressure gage.
- Stop engine after reaching the upper switching off pressure.

Upper switching off pressure = 52-57 bar (764-838 lb sq in)





- If the reservoir pressure (pressure gage) drops by more than 5 bar (71 psi) within 5 minutes, disconnect the return line on the power flow regulator.
- If leak oil runs out of the return line bore on the power flow regulator, the power flow regulator leaks and must be replaced.
- If no leak oil runs out and the reservoir pressure still drops, the brake booster has an internal leak and must be replaced.