Leak Test

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

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

Fig 1: Identifying VAS 6721 Shut-Off Valves

Courtesy of AUDI OF AMERICA, LLC

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

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

• Normally (see note), the vacuum should be between 600 and 950 mbar (9 and 13 psi) (depending on the engine installed).

-- Open the shut-off valve -C- to evacuate the brake booster.

Fig 2: Identifying VAS 6721 Shut-Off Valves

Courtesy of AUDI OF AMERICA, LLC

-- Turn off the engine.

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

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

TIP:

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

-- If the pressure drop is large, look for the area with the leak:

A - Testing the Vacuum Near the Brake Booster

Fig 3: Identifying VAS 6721 Shut-Off Valves

Courtesy of AUDI OF AMERICA, LLC

-- Close the shut-off valve -A- after creating the vacuum to check the brake booster vacuum system.

B - Testing the Vacuum Near the Check Valve, Vacuum Hoses with Connectors and Vacuum Pump/Intake Manifold

Fig 4: Identifying VAS 6721 Shut-Off Valves

Courtesy of AUDI OF AMERICA, LLC

-- Close the shut-off valve -C- after creating the vacuum to check the vacuum system from the Brake Servo Tester :VAS6721  up to the intake manifold or up to the vacuum pump.

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