Vacuum, Checking

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NOTE:

The average earth atmospheric air pressure at sea level (N. N.) is 1013 mbar (15 psi) and it decreases dramatically at higher altitudes (approximately 100 mbar (1.5 psi) every 1000 meters higher) Local and time fluctuations will influence the vacuum.

A cold engine, the A/C switched being on and even only the engine idling can negatively influence the vacuum.

-- Check all the vacuum hoses beforehand for damage (for example, tears or damaged caused by animals) and make sure they are secure

-- Connect the Brake Servo Tester VAS6721. Refer to Brake Servo Tester VAS6721, CONNECTING .

-- Open the shutoff valve -A-.

-- Close the shutoff valves -B+C-.

Fig 1: Identifying VAS 6721 Shut-Off Valves

Courtesy of AUDI OF AMERICA, LLC

-- Start the warm (above 60 °C (140 °F)) engine and press the accelerator pedal one time quickly (engine RPM higher than 2, 000).

-- Read the measured value displayed.

Normally (see note) the vacuum should be between 600 and 950 mbar (9 to 14 psi) (depending on the engine installed).

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

-- Create the vacuum using a Hand Vacuum Pump VAS6213 for comparison purposes. Refer to VACUUM, CREATING WITH Hand Vacuum Pump VAS6213 .

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