What Causes the Brakes to Suddenly Become Hard and Difficult to Stop?
2 Answers
When the brakes suddenly become hard and difficult to stop, it is usually due to a vacuum booster pump leak or malfunction. The force applied to the brake pedal is amplified by the brake booster pump, and if it fails, braking becomes difficult. Another scenario is pressing the brakes after the engine has been turned off, which is also related to the brake booster pump. The brake booster pump only continuously generates vacuum when the engine is running. When the engine is off, it relies on the residual vacuum, which typically depletes after a few presses. However, this issue resolves after restarting the engine and is not considered a malfunction. The vacuum booster pump only generates vacuum and provides assistance when the engine is running. If the engine is off, it no longer produces assistance, and the remaining vacuum will be completely depleted after pressing the brakes. If you notice the brakes becoming hard while driving, the first thing to do is to release the accelerator and slow down, then try pressing the brakes multiple times to restore braking force. For manual transmission vehicles, downshifting can help reduce speed, and you can also use speed bumps to gradually bring the car to a stop.
I've been driving my old car for over a decade, and once the brakes suddenly became very stiff, almost causing me to hit the car in front. The reason was likely a failure in the brake system's vacuum booster—either a leak in the vacuum hose or a broken booster pump. Without the assistive force, the brakes became extremely hard. Insufficient or leaking brake fluid is another common factor, as low fluid levels lead to inadequate pressure. Additionally, a faulty master cylinder or blocked brake lines can cause this issue. After that experience, I learned to regularly check the brake fluid level, ensuring it's within the normal range in the reservoir and that the fluid is clear and free of bubbles. If you encounter this problem, it's crucial to slow down and pull over immediately—don't delay, as it's a serious safety concern. It's best to take the car to a professional repair shop, as they can test whether the vacuum system is leaking.
