34 00 519 Checking service brake: high- and low-pressure tests

WARNING: This page is about a different car, the 2007 BMW 550i, 2006 BMW 550i, 2005 BMW 545i, and 2004 BMW 545i. However, it is still accessible from the selected car via links, so may be relevant.

IMPORTANT: The high/low-pressure test (leakage test) must be carried out with the engine switched off.

Observe safety instructions on raising the vehicle. Refer to 00 .. ... LIFTING VEHICLE WITH A LIFTING PLATFORM .

High-pressure test (leakage test):

Perform test on both brake circuits.

1st brake circuit, front axle.

2nd brake circuit, rear axle.

Remove bleeder screw, connect pressure tester and bleed.

Fig 1: Locating Bleeder Screw

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Load brake pedal with a force and block brake pedal with pedal support.

After 2 minutes, pressure is permitted to drop by max. 8 %.

Fig 2: Securing Brake Pedal With Pedal Support

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Low-pressure test:

Perform test on both brake circuits.

Reset pedal support until test pressure in braking system is 2-5 bar.

Vehicle and measuring apparatus must remain steady as vibrations will distort the result.

Pressure must remain constant for a test period of 5 minutes.

Check all rubber parts in case of excessive pressure drop.

Bleed brake calipers and wheel brake cylinders after finishing test.

Fig 3: Identifying Pressure Tester

Courtesy of BMW OF NORTH AMERICA, INC.