Sometimes the pedal can become tight (stiff) and be hard to press; in most circumstances the car will continue to brake correctly, but it’s an unnerving feeling for a driver and an issue that should be resolved as soon as possible.
How this system works:
Brake systems on modern vehicles are vacuum assisted via a brake booster. A vacuum diaphragm essentially multiplies the force that you are applying to the brake pedal, thus making it easier for you to brake, and giving you more control.
When the brake pedal is pressed, the vacuum source is closed off, which allows atmospheric pressure to enter one side of the vacuum diaphragm. This causes the master cylinder pistons to apply the brakes. When you remove your foot from the brake pedal, vacuum returns to both sides of the diaphragm, and the master cylinder pistons return to their normal position.
Common reasons for this to happen:
- Faulty brake booster: The most common culprit of a hard brake pedal is the brake booster. A faulty brake booster will be unable to provide vacuum assist, meaning that you will be attempting to depress the brake pedal with no assistance.
- Vacuum hose is leaking: Most often, the entire booster is broken, but sometimes it is one individual component at fault. In some cases, the booster vacuum line hose can begin to leak, which will limit the effectiveness of the vacuum assist.
- Check valve malfunction: The check valve, which is responsible for allowing air to exit the booster but not enter it, can also malfunction or break.
- Wrong-size parts: If your booster has been replaced recently, but your brake pedal is still hard, it could be that the replacement parts were the incorrect size. Adding a brake booster of the wrong weight, or a vacuum hose of the wrong size is a common mistake among inexperienced mechanics.
How important is this service?
Even though your brakes are hard to press, chances are that they still work. However, the braking will be unassisted, meaning you’ll have to press the pedal a lot harder to get your vehicle to stop. Have your vehicle inspected as soon as possible to diagnose the issue.