Leak Test
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 (1.4 psi) every 1000 meters (0.62 miles) higher). Local and time fluctuations also influence the vacuum.
A cold engine, the A/C switched on and even only the engine 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 BOOSTER TESTER, CONNECTING .
-- Open the shutoff valve -A-.
-- Close the shutoff valves -B and C-.
-- 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 (8.7 and 13.77 psi) (depending on the engine installed).
-- Open the shutoff valve -C- to evacuate the brake booster.
-- Turn off the engine.
-- Read the displayed measured value and write it down.
- The vacuum may drop 400 mbar (5.8 psi) in 12 hours.
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
-- Close the shutoff valve -A- after creating the vacuum to test the brake booster vacuum system.
B - Testing the Vacuum Near the Check Valve, Vacuum Hoses with Connectors and Vacuum Pump/Intake Manifold
-- Close the shutoff valve -C- after creating the vacuum to check the vacuum system of the :VAS6721 up to the intake manifold or up to the vacuum pump.
Opening the shutoff valve -B- makes it easier to remove the hose connections and the adapter.