Vehicles after change point in 1982 CHECKING POWER BRAKE SYSTEM Discharge hydraulic reservoir by operating brake pedal about 20 times with same amount of force required for full stop braking action with the engine stopped. Pull off wires and unscrew hydraulic pressure switch. Mount Special Tool 34 3 160. Installation: Tightening torque*.  * See Specifications
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Connect pressure meter 32 4 000 on Special Tool 34 3 160. Shut both valves (1 and 2). |  |
Power Flow Regulator and Brake Booster Leak Test: Run engine and observe pressure meter. Stop engine when reaching the top switching off pressure value*. * See Specifications
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If reservoir pressure (pressure gauge) drops by more than 5 bar (71 psi) within 5 minutes, disconnect return line on power flow regulator. If oil leaks at return line bore in power flow regulator, power flow regulator has a leak and must be replaced. If oil does not leak and reservoir pressure still drops, brake booster has internal leakage and must be replaced. |  |
Checking Function of Hydraulic Reservoir: Discharge reservoir pressure to zero on pressure gauge by operating brake pedal about 20 times. Start engine and observe pressure gauge. Pressure gauge should show a value as indicated in diagram immediately. Replace hydraulic reservoir if this value is not reached or exceeded. |  |
A = Gas charge pressure in bar B = Hydr. reservoir temperature in °C Permissible Gas Charge Pressure for Hydraulic Reservoir in Different Temperature Conditions |  |
Checking Function of Power Flow Regulator: Start engine. Pressure rises up to switching off pressure*. Reduce reservoir pressure to switching-on pressure value* on pressure gauge by operating brake pedal with engine running. Afterwards power flow regulator will switch to charging reservoir; the pressure rises again. Replace power flow regulator when test values are not reached. Discharge reservoir pressure to zero on pressure gauge by operating brake pedal about 20 times. Remove pressure meter. Check oil level in supply tank. * See Specifications
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Checking Function of Brake Booster with Tandem Master Cylinder: Unscrew bleeder screw on caliper. Connect pressure tester and bleed. |  |
Mount pedal force tester on brake pedal. Apply a force* on brake pedal withe engine running (fully charged hydraulic reservoir). This should cause the hydraulic line pressure of service brake to show specified pressure*. Replace brake booster, if these values are not reached on a brake system in perfect condition. Note: This test does not include the service brake leak test. * See Specifications
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