34 00 519 Checking service brake: high- and lowpressure tests

WARNING: This page is about a different car, the 2005 BMW 645Ci and 2004 BMW 645Ci. 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: Performing High-Pressure Test (Leakage Test)

Courtesy of BMW OF NORTH AMERICA, INC.

Load brake pedal with a force and block brake pedal with pedal support, refer to BRAKES - TECHNICAL DATA - 645CI .

Fig 2: Blocking Brake Pedal With Pedal Support

Courtesy of BMW OF NORTH AMERICA, INC.

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

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.

Fig 3: Identifying Low-Pressure Test Measuring Apparatus

Courtesy of BMW OF NORTH AMERICA, INC.

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.