Testing Power Brake Assist and Vacuum Brake Booster
Vacuum Brake Booster: Testing and Inspection
BRAKE BOOSTER OPERATING TEST
1. For simple checking of the brake booster operation, carry out the following tests:
(1) Run the engine for one or two minutes, and then stop it. If the pedal depresses fully the first time but gradually becomes higher when
depressed succeeding times, the booster is operating properly. If the pedal height remains unchanged, the booster is defective. Go to step 2.
(2) With the engine stopped, step on the brake pedal several times. Then step on the brake pedal and start the engine. If the pedal moves
downward slightly, the booster is in good condition. If there is no change, the booster is defective. Go to step 3.
(3) With the engine running, step on the brake pedal and then stop the engine. Hold the pedal depressed for 30 seconds. If the pedal height does
not change, the booster is in good condition, if the pedal rises, the booster is defective.
2. If the above three tests are okay, the booster is OK. If one of the above three tests is not okay, the check valve, vacuum hose, or booster is
defective. Check the check valve, vacuum hose for leaks, high volume engine vacuum applied to booster. Repair or replace as necessary. If these
are OK, replace booster and repeat this test starting at Step 1.
