Your brake master cylinder keeps your brakes functioning smoothly, so it's important to keep it properly maintained.

What Does the Brake Master Cylinder Do?

When you think about your brakes, you likely imagine the parts you can see behind each wheel. Most cars have disc brakes with a caliper, pad and large, round rotor that are all visible. Then there are the parts you can’t see until you lift the hood, like the brake master cylinder. This part helps stop your car, so it’s important to keep it properly maintained. Here’s how it keeps your brakes functioning smoothly and how to know if something is wrong.

What This Critical Brake Part Does

Press on the brake pedal and the brake master cylinder converts the pressure from your foot into hydraulic pressure. This hydraulic pump forces brake fluid through a series of pipes and hoses to engage your brakes. Take your foot off the brake pedal to remove the hydraulic pressure and the brakes are released. Sounds simple, right?

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Well, it is, but it’s also a delicate system. If the pressure is wrong, your brakes won’t work. There are several reasons the pressure might be off, such as dirt or air in the lines or low brake fluid. That’s why it’s important to maintain your brake system and pay attention to how it operates from day to day.

Maintenance: Checking the Brake Fluid

Check your brake fluid by looking inside the reservoir on top of the master cylinder. It has a cap that either unscrews or pops off with a screwdriver. Be very careful when you remove the lid and make sure dirt doesn’t fall into the reservoir.

There’s a fill line on the inside of the cylinder that’s about half an inch from the top of the chamber. Your brake fluid should reach this line. If it doesn’t, then it needs to be topped off. Also, check the color of the fluid. If the color is dark brown or black, then the seals within the master cylinder are breaking down and you should take your car in for a checkup.

This whole process should be done quickly. You want to limit exposure to the air to prevent dirt or water vapor from being introduced into the system.

Pay Attention to Signs of Trouble

Once you drive your car for awhile, you learn how your brakes feel when you press the brake pedal. It becomes second nature to slow down gently and you don’t really have to think about how hard you press. The moment you push on that pedal and it doesn’t react as expected, you know there’s a problem.

If you press on the brake pedal and it takes longer than normal for the brakes to engage, that’s a sign of trouble and possibly a failing master cylinder. The brake pedal may also start to feel different under your foot. It might get mushy or spongy or sink slowly to the floor. If you experience any of these problems, you should have your brakes checked.

It’s essential to maintain your whole braking system so that you’re safe on the road. When was the last time you had your brakes checked? If you can’t remember, then now is the time to make sure they’re up to snuff and ready for the road.

Check out all the brake system products available on NAPA online or trust one of our 16,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on maintaining your brakes, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Nicole Wakelin.

about author

Nicole Wakelin

Nicole Wakelin covers the automotive industry as a freelance journalist for a variety of outlets. Her work includes news pieces, podcasts, radio, written reviews, and video reviews. She can be found in The Boston Globe, CarGurus, BestRide, US News and World Report, and AAA along with lifestyle blogs like Be Car Chic, The Other PTA, and She Buys Cars. She is active on social media with a large following on both Twitter and Instagram and currently serves as Vice President of the New England Motor Press Association.

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