Vacuum Pump: Testing and Inspection
Brake Booster Vacuum System, Checking
=> [ , Connecting ]
=> [ Vacuum, Checking ]
=> [ Leak Test ]
=> [ Vacuum, Creating using ]
The following checks will be helpful when performing Fault Finding if there are complaints regarding the brake booster or the so-called hard brake pedal.
The following components are included in the check:
• Brake booster
• Seal between the brake master cylinder and the brake booster
• Check valve
• Vacuum hoses and connectors
• Vacuum pump (if equipped)
Keep the geographical surrounding in mind when evaluating the measured results. The higher above sea level, the lower the air pressure.
Always observe all test requirements before checking the vacuum system:
• Check all the vacuum hoses for damage (for example, tears or damaged caused by animals) and make sure they are secure
• Maintain clean working conditions when working on the vacuum system
• Clean the engine compartment before starting, if necessary
Special tools, testers and auxiliary items required
• Brake Servo Tester (VAS 6721)
Brake Servo Tester (VAS 6721), Connecting
Special tools, testers and auxiliary items required
• Brake Servo Tester (VAS 6721)
• Hand Vacuum Pump (VAS 6213)
- Remove the vacuum hose from the brake booster.
Pressing the brake pedal a few times beforehand makes it easier to remove the vacuum hose.
- Connect the (VAS 6721) - see following illustrations -.
- Connect the (VAS 6721) hose - A - too the vacuum hose and push the adapter - C - into the brake booster.
Vacuum, Checking
Special tools, testers and auxiliary items required
• Brake Servo Tester (VAS 6721)
• Hand Vacuum Pump (VAS 6213)
• 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.
• 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 (VAS 6721).
- Open the shut-off valve - A -.
- Close the shut-off valves - B + C -.
- Start the warm engine (above 60 °C (140 °F)) and press the accelerator pedal one time quickly (engine RPM higher than 2,000).
- Read the measured value displayed.
Normally (see note) the vacuum should be between 600 and 950 mbar (depending on the engine installed).
Check the vacuum system for leaks if the measured value is not reached, even though all requirements (see notes).
- Create the vacuum using a (VAS 6213) for comparison purposes.
Opening the shut-off valve - B - makes it easier to remove the hose connections and the adapter.
Leak Test
Special tools, testers and auxiliary items required
• Brake Servo Tester (VAS 6721)
• 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.
• 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 (VAS 6721).
- Open the shut-off valve - A -.
- Close the shut-off valves - B + C -.
- Start the warm engine (above 60 °C (140 °F)) 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....
1 - Brake Booster
or in the
2 - 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 (VAS 6721) vacuum 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.
Vacuum, Creating using Hand Vacuum Pump (VAS 6213)
Special tools, testers and auxiliary items required
• Hand Vacuum Pump (VAS 6213)
• Brake Servo Tester (VAS 6721)
In certain situations, the vacuum can be created using a (VAS 6213) instead of using the engine or a vacuum pump.
- Connect the (VAS 6213) to the vacuum hose on the connection - B - on the (VAS 6721).
- Open the shut-off valve - B -.
- Create the vacuum using the (VAS 6213) until a vacuum between 600 and 950 mbar on the (VAS 6721) is displayed.
- Perform the tests.