Low Pressure Test
- Remove left microfilter for interior ventilation. See 64 31 010 REPLACING MICROFILTER FOR INTERIOR VENTILATION
- Pull hose off connection. Install Vacuum Tester (34 3 100) between connection and vacuum hose on non-return valve. See Fig 1.
- Start engine and check buildup of partial vacuum. Stop engine.
- Press brake pedal to set a partial vacuum of no more than 11.6 psi (.8 bar) and wait for value to stabilize.
- When brake pedal is not pressed, partial vacuum is allowed to drop by maximum.8 psi (.06 bar) over a test period of one minute. If specified values are not reached:
- Check line connections for vacuum seal.
- Replace vacuum non-return valve.
- Check seal between brake booster and brake master cylinder (sealing ring) for perfect condition and correct seating.
- If specified values are not achieved when test is repeated, replace brake booster. See BRAKE BOOSTER under REMOVAL & INSTALLATION.
Courtesy of BMW OF NORTH AMERICA, INC.