Leak Test

WARNING: This page is about a different car, the 2023 Volkswagen Atlas. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

The average earth atmospheric air pressure at sea level (N. N.) is 1013 mbar (14.69 psi) and it decreases dramatically at higher altitudes (approximately 100 mbar (1.45 psi) every 1000 meters (0.62 mile) higher) Local and time fluctuations also influence the vacuum.

A cold engine, the A/C switched on as well as the engine simply idling can negatively influence the vacuum.

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

-- Connect the :VAS6721 . Refer to Brake Servo Tester .

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

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

Fig 1: Identifying VAS 6721 Shut-Off Valves

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

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

Normally (see note), the vacuum should be between 600 and 950 mbar (8.7 and 13.77 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 VOLKSWAGEN GROUP OF AMERICA, INC.

-- Turn off the engine.

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

The vacuum may drop 400 mbar (5.8 psi) within 12 hours.

If the drop in vacuum is greater, check for leaks in the area of the....

Brake Booster
or the
Check Valve, the Vacuum Hoses with Connectors and the Vacuum Pump/Intake Manifold
are present.

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

Vacuum, Checking near Brake Booster:

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

Fig 3: Identifying VAS 6721 Shut-Off Valves

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

Vacuum, Checking near Check Valve, Vacuum Hoses with Connectors and Vacuum Pump/Intake Manifold

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

Fig 4: Identifying VAS 6721 Shut-Off Valves

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

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