Leak Test
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 will influence the vacuum.
Idling the engine has a negative effect on creating a 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 BOOSTER TESTER, CONNECTING .
-- Open the shut-off valve -A-.
-- Close the shut-off valves -B+C-.
-- Start the warm (above 60 °C) 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 (depending on the engine installed).
-- Open the shut-off valve -C- and evacuate the brake booster.
-- Turn off the engine.
-- Read the measured value displayed and write it down.
- The vacuum may drop 400 mbar within 12 hours.
If the drop in vacuum is greater, check the....
- Brake Booster
or in the
- Check valve, vacuum hoses and 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 shut-off valve -A- after creating the vacuum to test the brake booster vacuum.
Vacuum test near the check valve, vacuum hoses and connections and vacuum pump/intake manifold
-- Close the shut-off valve -C- after creating the vacuum to check the vacuum system of 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.