Compass 2WD L4-2.0L VIN 0 (2007)
Vacuum Brake Booster: Testing and Inspection
POWER BRAKE BOOSTER
BASIC TEST
1. With engine off, depress and release the brake pedal several times to purge all vacuum from the power brake booster.
2. Depress and hold the pedal with light effort (15 to 25 lbs. (6.8 to 11.3 kg) pressure), then start the engine.
The pedal should fall slightly, then hold. Less effort should be needed to apply the pedal at this time. If the pedal fell as indicated, perform the
VACUUM LEAK TEST listed after the BASIC TEST. If the pedal did not fall, continue on with this BASIC TEST.
3. Disconnect the vacuum hose at the vacuum check and tee-in a vacuum gauge.
4. Start the engine.
5. When the engine is at warm operating temperature, allow it to idle and check the vacuum at the gauge.
If the vacuum supply is 12 inches Hg (40.5 kPa) or more, the power brake booster is defective and must be replaced. If the vacuum supply is below 12
inches Hg, continue on with this BASIC TEST.
6. Shut off the engine.
7. Connect the vacuum gauge to the vacuum reference port on the engine intake manifold.
8. Start the engine and observe the vacuum gauge.
If the vacuum is still low, check the engine tune and repair as necessary. If the vacuum is above 12 inches, the hose or check to the booster has a
restriction or leak.
Once an adequate vacuum supply is obtained, repeat the BASIC TEST.
VACUUM LEAK TEST
1. Disconnect the vacuum hose at the vacuum check and tee-in a vacuum gauge.
2. Start the engine.
3. Allow the engine to warm up to normal operating temperature and engine idle.
4. Using vacuum line pliers, close off the vacuum supply hose near the booster and observe the vacuum gauge.
If the vacuum drop exceeds 1.0 inch Hg (3.3 kPa) in one minute, repeat the above steps to confirm the reading. The vacuum loss should be less than 1.0
inch Hg in one minute time span. If the loss is more than 1.0 inch Hg, replace the power brake booster. If it is not, continue on with this test.
5. Remove the pliers from the hose temporarily.
6. Apply light effort (approximately 15 lbs. (6.8 kg) of force) to the brake pedal and hold the pedal steady. Do not move the pedal once the pressure
is applied or the test results may vary.
7. Have an assistant reattach the pliers to the vacuum supply hose.
8. Allow 5 seconds for stabilization, then observe the vacuum gauge.
If the vacuum drop exceeds 3.0 inches Hg (10 kPa) in 15 seconds, repeat the above steps to confirm the reading. The vacuum loss should be less than
3.0 inches Hg in 15 seconds time span. If the loss is more than 3.0 inches Hg, replace the power brake booster. If it is not, the booster is not defective.
