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Vacuum, Checking

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NOTE:

The average earth atmospheric air pressure at sea level (N. N.) is 1013 mbar and it decreases dramatically at higher altitudes (approximately 100 mbar every 1000 meters higher) Local and time fluctuations also influence the vacuum.

Idling the engine has a negative effect on creating a vacuum.

-- Check all vacuum hoses beforehand for damage (for example, tears or damage caused by animals) and for a secure fit.

-- Connect the : VAS6721  . Refer to BRAKE BOOSTER TESTER, CONNECTING .

-- Open the shut-off valve -A-.

-- Close the shut-off valves -B and C-.

Fig 1: Identifying VAS 6721 Shut-Off Valves
GWWN47-10210Courtesy of AUDI OF AMERICA, LLC

-- Start the warm (above 60 °C) engine and press the accelerator pedal one time quickly (engine speed higher than 2, 000 RPM).

-- Read the displayed measured value.

Normally (see note), the vacuum should be between 600 and 950 mbar (depending on the engine installed).

Check the vacuum system for leaks if the measured value is not reached, even though all requirements (see notes) are met.

-- Create a vacuum using the : VAS6213  for comparison. Refer to VACUUM, CREATING WITH HAND VACUUM PUMP .

Opening the shut-off valve -B- makes it easier to remove the hose connections and the adapter.