Leak test
Pic. 6.14. Checking the brake booster
Start the engine and stop it after 1 or 2 minutes. Slowly press the brake pedal at least 3 times (pic. 6.14).
Note. The brake booster is sealed if the distance traveled by the brake pedal decreases with each depression.
If not, check the vacuum check valve.
If the vacuum check valve is OK, replace the brake booster assembly.
Press the brake pedal with the engine running and, without releasing, turn off the engine.
If the residual brake pedal travel remains unchanged after 30 seconds of holding the brake pedal, the booster is sealed.
If not, check the vacuum check valve.
If the vacuum check valve is OK, replace the brake booster assembly.
Health check
Pic. 6.15. Checking the performance of the brake booster
Depress the brake pedal several times with the ignition off and check for any change in the residual brake pedal travel (pic. 6.15).
Press the brake pedal and start the engine.
If the brake pedal starts to drop, then the booster is good. If not, check the vacuum check valve.
If the vacuum check valve is OK, replace the brake booster assembly.
Vacuum Check Valve
Check vacuum check valve.
Remove the vacuum check valve from the brake booster.
Pic. 6.16. Vacuum Check Valve
Make sure the valve allows air to flow from the booster to the engine and does not flow in the opposite direction (pic. 6.16).
Note. If any malfunction is found, replace the vacuum check valve.