Low Pressure Test

2013 Mini Cooper Countryman, Standard TransSECTION Low Pressure Test
WARNING: This page does not describe the selected car, but rather 92 other vehicles, including the 2002 BMW Z3, 2002 BMW M Roadster, 2002 BMW M Coupe, 2001 BMW Z3, and 2001 BMW M5. However, it is still accessible from the selected car via links, so may be relevant.
  1. Remove left microfilter for interior ventilation.
  2. Pull hose off connection. Install Vacuum Tester (34 3 100) between connection and vacuum hose on non-return valve. See Fig 1.
  3. Start engine and check buildup of partial vacuum. Stop engine.
  4. Press brake pedal to set a partial vacuum of no more than 11.6 PSI (.8 bar) and wait for value to stabilize.
  5. When the brake pedal is not pressed, the partial vacuum is allowed to drop by maximum .8 PSI (.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, replace the brake booster.
Fig 1: Installing Vacuum Tester
G00103324Courtesy of BMW OF NORTH AMERICA, INC.
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.