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HOMESERVICE MANUALSBMW2004325CI CONVERTIBLE (E46) L6-2.5L (M56)REPAIR AND DIAGNOSISBRAKES AND TRACTION CONTROLTESTING AND INSPECTIONCOMPONENT TESTS AND GENERAL DIAGNOSTICSCHECKING BRAKE BOOSTER (LOW-PRESSURE TEST)
2004 BMW 325Ci Convertible (E46) L6-2.5L (M56)

Checking Brake Booster (Low-Pressure Test)

2004 BMW 325Ci Convertible (E46) L6-2.5L (M56)SECTION Checking Brake Booster (Low-Pressure Test)






- Pull hose off connection. Install vacuum tester 34 3 100 between connection and vacuum hose on non-return valve.
- Start engine.
- Check buildup of partial vacuum.
- Switch off engine.
- Press brake pedal to set a partial vacuum of no more than 0.8 bar and wait for value to stabilize.
- When the brake pedal is not pressed, the partial vacuum is allowed to drop by max. 0.06 bar over a test period of 1 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 the specified values are not achieved when the test is repeated, you must replace the brake booster.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.