Symptoms of a Bad or Failing Power Brake Booster

The purpose of a brake booster is to provide power assistance to the braking system, meaning you do not have to put a lot of force on the brakes for them to actually engage. The brake booster is located between the brake pedal and master cylinder and uses a vacuum to overcome the fluid pressure in the brake system. If your brakes are not working properly, the vehicle should not be driven. The brake booster is an essential part of the braking system, so keep an eye out for the following 3 symptoms so you can have them repaired right away:

1. Hard brake pedal

The primary indicator of a bad brake booster is an extremely difficult-to-push brake pedal. This issue may occur gradually or appear all at once. In addition, the brake pedal will not return to its original position after being pressed. As soon as you notice your brake pedal is hard to engage, contact a professional mechanic to have your brake booster replaced. It is critical that brake booster faults are repaired quickly — the car is not safe to drive with a failed brake booster.

2. Longer stopping distance

Along with a hard brake pedal, you may notice it takes the vehicle longer to actually stop. This is because you are not getting the actual power boost needed to properly stop the vehicle. A longer stopping distance can be hazardous in all types of weather because it can make your car unpredictable. This issue should be looked at by a mechanic as soon as you notice it.

3. Engine stalls when brakes are applied

When the brake booster is failing it can draw excess vacuum from the engine. This occurs when the diaphragm inside the brake booster fails and allows air to bypass the seal. The brakes are then pressed, the engine feels like it will stall, and the idle can drop. In addition to the decreased brake performance, a stalling engine can cause serious issues.

Test the Booster

Since most vehicles use a vacuum system, the brake booster can be tested at your home. Observe the following 3 steps:

  1. With the engine off, pump the brakes — about five or six times is sufficient. This depletes the stored vacuum.

  2. Turn the engine on while pushing down lightly on the brake pedal. If your brake booster is working normally, the pedal will fall away a little, but then become firm.

  3. If your brake booster is not working correctly, nothing will happen, or the brake pedal will push back against your foot once the engine starts. This could be a sign of a brake booster problem or an issue with the vacuum hose.

If you notice the brake pedal is difficult to push, higher than normal, and your vehicle takes longer to stop, have a mechanic inspect it to be safe on the road. If needed, the mechanic will replace your brake booster in a timely manner so you can safely drive your vehicle again.


Next Step

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