Why does the brake suddenly become hard?

[VonChase]

There are several main reasons why the brake suddenly becomes hard: 1. Problem with the brake booster pump: If the brake suddenly becomes hard while driving, it may be caused by a vacuum tube leak or blockage in the brake booster pump. In this case, you should stop the car immediately for inspection and replace it if necessary. 2. Foreign objects adhering to the brake pads or calipers: If there are foreign objects stuck to the brake pads or calipers, the friction from these objects during braking can also create a sensation of the brake becoming hard. In this situation, simply cleaning them will resolve the issue. 3. Vehicle ABS system intervention: When the vehicle performs an emergency brake, the ABS system intervenes in the braking system to prevent wheel lock-up and loss of control, which can cause the brake pedal to have a rebound effect. This is a normal phenomenon, and gently pressing the brake again will restore normal operation.

[Frederick]

I remember that time when I was driving and the brakes suddenly became stiff, feeling like they wouldn't budge, which gave me quite a scare. This is usually caused by a problem with the brake booster, such as a vacuum pump or a leak in the tubing, which causes the brakes to lose their normal power-assist function. Additionally, if you press the brakes after the engine stalls, the booster can't retain the vacuum, making the brakes stiff. Insufficient brake fluid or air in the system can also lead to this condition due to inadequate hydraulic pressure. I immediately pulled over and checked the brake fluid reservoir—it was too low. Later, I discovered that the booster's sealing ring had aged and was leaking. This incident taught me that it's essential to regularly check the brake fluid and the booster system, especially in older cars that are prone to oil and air leaks. If you ever encounter abnormally stiff brakes, don't hesitate—pull over to a safe spot immediately and call for help. Forcing the car to drive could lead to a major accident.

[SilasLynn]

When I work on car repairs, I often encounter situations where the brakes become stiff. The main causes include vacuum booster failure, such as diaphragm damage or vacuum hose leaks; there's also brake fluid leakage leading to insufficient system pressure; sometimes air entering the hydraulic lines can cause this as well. Simply put, you can first check the brake fluid reservoir in the engine compartment to see if the fluid level is too low, while also looking for any signs of oil leakage. If it's a booster issue, start the engine before driving—normally the assist should feel smoother; if the brakes become stiff, stop immediately to check. During repairs, you might need to replace parts or bleed the brake system—safety first, don't risk driving.

[StOlive]

I've experienced the brake pedal becoming hard several times, mostly due to a faulty vacuum booster or interrupted engine vacuum supply. For example, if you press the brake after turning off the engine, the booster won't recover upon next startup. Brake fluid leakage or air entering the pipelines can also cause the pedal to become hard and unresponsive. The key is to stay calm, immediately slow down and pull over. Don't push your luck by continuing to drive, as extended braking distance is extremely dangerous.