BMW 1 Quiz
Brake System

Brake Booster Check

In this manual: Brake System
Introduction — 10Owner's Manual — 29Routine Care and Maintenance — 30Engine — 18Cooling and Heating Systems — 13Fuel and Exhaust Systems — 29Engine Electrical Equipment — 20Manual Transmission — 4Automatic Transmission — 4Clutch and Drive Shafts — 12Brake System — 19Suspension and Steering — 22Body — 36Body Electrical Equipment — 34Electrical Circuit Diagrams — 30On-board diagnostic system — 5
~1min read

If considerable force is required on the brake pedal to achieve the necessary braking effect, check the brake booster.

PROCEDURE

1. With the engine off, depress the brake pedal at least 10 times. Then, keeping the pedal depressed, start the engine. The pedal force should decrease. If so, the brake booster is serviceable.
2. If not, disconnect the vacuum hose from the booster and start the engine. Place a finger over the end of the vacuum hose and check for vacuum.
3. If there is no vacuum: Check the vacuum hose for leaks and damage. Replace if necessary. Tighten all clamps.
4. Diesel engine: Disconnect the vacuum hose from the vacuum pump and check for vacuum with a finger.
5. If there is vacuum: Measure the vacuum value. If necessary, replace the brake booster (dealer service).

* Always replace the check valve in the vacuum line, as the booster diaphragm may be damaged by fuel vapor (gasoline engines with a faulty check valve). The arrows on the check valve must point in the direction of the intake manifold.

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