Most vacuum-assist power brakes function because of engine vacuum. Here are four possible reasons your brake pedal is hard to press: Why is My Brake Pedal Hard to Push Down? Bad Brake BoosterĪ bad brake booster is one that can no longer maintain vacuum pressure. Now that you understand how your power brakes system works, it may be easier to diagnose your stiff brake pedal. The master cylinder then sends brake fluid to the brake calipers or wheel cylinder (if the vehicle has rear drum brakes), causing the brake pads or rear shoes to rub against the rotors or rear drums and slow your vehicle. In turn, this power-assisted pushrod applies force to the master cylinder’s pushrod, which would otherwise be very difficult to move. In the back chamber, pressing the brake pedal allows air to enter.īecause the pressure from the air chamber is greater than the pressure in the vacuum chamber, the diaphragm - and a pushrod connected to it - is pulled toward the low-pressure side.

In the front chamber, air is removed to create a low-pressure vacuum. This system, also known as power brakes, allows you to stop a two-ton vehicle with just your foot!Ĭommon vacuum brake boosters, located between the master cylinder and brake pedal, have two chambers separated by a diaphragm within it. Brake boosters multiply the force applied to your brake pedal, and they work in tandem with the hydraulic fluid in the brake lines. In most cases, stiff brakes are caused by problems with the brake booster.

Naturally, since it becomes harder to slow down your car, a stiff brake pedal is a serious safety hazard that should be serviced right away.īut what causes a brake pedal to be hard in the first place? Read on to learn four potential reasons for why your brake pedal is hard to press.

If your brake pedal gets stiff while driving, you might feel like you have to practically stand on the pedal to slow down or stop your vehicle.

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