Sinking Brake Pedal: A Look At This Scary Occurrence

For any driver, it can be terrifying to try and use the brakes and have the pedal touch the floor without anything happening. This is what’s known a sinking brake pedal, and it can have a variety of causes. Here is a quick look at this issue for students considering a career in automotive repair and maintenance.

What Are the Main Causes of Sinking Brake Pedals?

Brakes which function properly are essential to auto safety, and a leak in the braking fluid can lead to issues while driving. The service brake system relies on hydraulic pressure, created by the forcing of air from the reserves of liquid brake fluid. A poorly-responding pedal is a good indicator of low hydraulic pressure caused by a leak or extra air in the fluid lines, which prevents the service brake system from creating the necessary friction to bring the car to a full or proper stop.
Another common cause familiar to those involved in an automotive career is a failure in the master cylinder. The brake master cylinder is a crucial component which converts the force from the brake pedal into hydraulic pressure, compressing the brake fluid in the rotors and stopping the wheels. If there is a malfunction in the master cylinder, there may be a general loss of pressure, which affects how well the braking system works as a whole, including pedal response.

Other Causes Students in Automotive Mechanics Training Should Know

Although the master cylinder and fluid leaks can cause a majority of sinking pedals, students enrolled in automotive mechanics training should be aware that these are not the only possible causes. A brake booster, which uses vacuum pressure to amplify force being applied to the brake pedal, can malfunction, reducing the force acting on the brake fluid.
Worn down brake pads or wheel bearings may also influence pedal efficiency. These are usually accompanied by a grinding metallic noise upon braking, which is caused by two brake components scraping together, and can also allow unwanted air into the brake system.

How to Fix and Prevent Sinking Brake Pedals

Keeping in mind that there are different options depending on the specific cause, there are common solutions to fix a sinking pedal. One process is known as ‘bleeding’ the brakes, which involves flushing excess air and braking fluid from the reservoir, and refilling the supply with new fluid. This process requires old brake fluid, which can become contaminated with dirt and other particles, to be replaced after being drained. Additionally, the brake pedal must consistently be pushed down then released, allowing the new fluid to travel through the braking system.

Although automotive components can degrade with time and use, there are certain steps which can help prevent frequent sinking pedals. One of the simplest methods is to drive responsibly, because riding the brake or using it excessively can contribute to overheating and a faster decline in the braking system. It’s also a good idea to make sure clients are using the right brake fluid, and replacing it annually to ensure that it is working properly, ensuring a safe drive for all involved.
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