The brake booster check valve sounds like a complicated thing, but its task is actually pretty simple: it ensures that the disc brakes will work even when the engine is turned off. But it's when the valve malfunctions that things really get complicated. A compromised valve could mean loss of pressure inside the booster, which in turn would mean a loss in brake function. If you have good reasons to believe that the check valve in your brake booster is damaged and not working properly, it must be replaced immediately. Otherwise, you run the risk of losing your brakes when you drive.
Difficulty level: Easy to moderate
- Wrench or screwdriver
- Hand-held vacuum pump
Step 1: Open the hood of your car and locate the brake booster. The valve is found near where the vacuum line connects to the dome-shaped brake booster.
Step 2: Look for and remove any clamps connecting the vacuum line to the check valve. Once the clamps are out of the way, remove the vacuum line itself.
Step 3: Using a wrench or screwdriver, detach the check valve from the booster. Apply 15-20 hg of pressure to the input end of the valve using the vacuum pump. If the valve is broken, the pump should indicate pressure lose.
Step 4: Install the new check valve on the booster and reattach the vacuum hose. Replace the clamps you may have removed as well.
Step 5: Close the hood, turn on the ignition and check the brakes for pressure. Once the engine is running, the brake pedal should go down slightly due to the vacuum generated inside the booster.
If the valve is installed correctly, the brakes should work long after the engine has stopped running. If not, the brake booster must also be faulty and have to be replaced as well.
To prevent damage to the vacuum lines, make sure that there is no pressure on the line before you try and remove it from the booster. To do so, press on the brake pedal several times with the engine off. This should remove any vacuum from the booster and the vacuum line.