What's the reason for hard brakes that don't stop the car?

[HaileyLee]

There are many factors that can cause hard brakes that don't stop the car: worn brake pads, air in the brake fluid, deteriorated brake fluid, brake fluid pipe leakage, stuck brake calipers not returning to position, worn master cylinder cup and leaking joints, or malfunctioning ABS pump. Since hydraulic brakes are used, when the engine is turned off, the hydraulic pump that drives the hydraulic brakes stops working, causing a sharp increase in brake damping, which is reflected on the pedal as it becomes very heavy and hard. The following are the standards for replacing brake pads: 1. Thickness: The normal thickness of brake pads is about 10mm, and they should be replaced if it is below 6mm. 2. Sound: If the car frequently makes abnormal noises when braking, it indicates that the brake pads are severely worn and should be replaced. 3. Pedal feel: When the brake pads are severely worn, their braking force decreases, so when you step on the brake, it will show symptoms of weakness, and the brake pads should be replaced promptly.

[TannerFitz]

Once when I was on a long drive, the brake pedal became so hard that I couldn't press it at all, with no braking feel whatsoever, and I almost got into an accident. It turned out later that the vacuum booster pump had failed—after the engine shut off, there was no vacuum support, so the pedal naturally became heavier. Other common causes include brake fluid leaks or air entering the system, leading to insufficient hydraulic pressure, making it hard to brake effectively. I recall that aging vacuum lines or a faulty check valve can also cause this. I suggest checking the fluid level immediately—if the reservoir is low on fluid, it might be a sign of a leak. Safety first—don't force it to drive; pull over as soon as possible and have it towed to a professional shop for repairs. During regular maintenance, pay extra attention: take a quick look at the brake fluid every time you change the oil to avoid unexpected issues.

[LaAlivia]

Hard brakes that don't stop the car are mostly due to vacuum booster failure, especially in older vehicles where rubber hoses deteriorate or the check valve fails—without the engine running, there's no vacuum assistance. Another possibility is air in the brake system or low hydraulic pressure, making the pedal stiff and ineffective. During inspection, first check the engine's operating condition; a stiff pedal when the engine is off is normal, but if it remains stiff while running, it's highly dangerous. Possible causes include low brake fluid or a faulty master cylinder—don't overlook potential leaks. If you encounter hard brakes, depress the clutch to slow down, shift to neutral, and pull over safely—don't risk driving further. Regular maintenance is key; check brake fluid levels every six months to ensure safety.

[BrodyFitz]

Car enthusiasts' experience tells you that hard brakes are often caused by a failed vacuum pump, making the pedal as heavy as a mountain without engine vacuum assistance. It could also be due to air bubbles in the brake fluid, which can't compress hydraulic pressure. Check if the brake fluid reservoir is leaking? Dirty or clogged fluid can also cause issues. If the brakes are hard and ineffective, the safest approach is to use engine braking—downshift and coast to a stop. During your next maintenance, flush the brake system and replace the fluid—prevention is always better than repair.