Leak Test

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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).

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

-- Open the shutoff valve -C- and evacuate the brake booster.

Fig 2: Identifying VAS 6721 Shut-Off Valves

Courtesy of AUDI OF AMERICA, LLC

-- Turn off the engine.

-- Read the measured value displayed and write it down.

The vacuum may drop 400 mbar (6 psi) within 12 hours.

If the drop in vacuum is greater, check the....

Brake Booster
or in the
Check Valve, Vacuum Hoses with Connections and Vacuum Pump/Intake Manifold
for leaks.

The vacuum will drop considerably within a few seconds if there are large leaks.

Checking the vacuum near the brake booster:

-- Close the shutoff valve -A- after creating the vacuum to test the brake booster vacuum.

Fig 3: Identifying VAS 6721 Shut-Off Valves

Courtesy of AUDI OF AMERICA, LLC

Vacuum test near the check valve, vacuum hoses and connections and vacuum pump/intake manifold

-- Close the shutoff valve -C- after creating the vacuum to check the Brake Servo Tester VAS6721 vacuum up to the intake manifold or up to the vacuum pump.

Fig 4: Identifying VAS 6721 Shut-Off Valves

Courtesy of AUDI OF AMERICA, LLC

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