What is brake fluid and why is it important?

January 01, 2022

You know about the important fluids in your car like your engine oil and windshield fluid. But what about brake fluid? If your mechanic tells you that you're running low on it, should you be skeptical? Is brake fluid a real thing or like "premium air" for your car? We go into all the details below so you know what to do with your vehicle.

What is brake fluid

Brake fluid is a very real thing that is a part of your hydraulic brake system. The brake fluid amplifies the pressure you apply to the brake pedal and turns it into braking force that actually stops the car. When you push the brake pedal, your foot's force is boosted, and the brake fluid runs through the brake lines until it reaches each wheel and pushes down the pistons which in turn push the brake pad onto the rotor to create friction and slow down the vehicle.

The brake fluid must be viscose and adapt to different temperatures so it can travel your brake system without freezing when it's cold and without fully melting when it's hot. Your brake fluid must also be the right type for your vehicle - it's best to check with your mechanic as some fluids can't be mixed together at all so you don't want to pour the wrong one into your system.

Why is brake fluid important

Brake fluid is important for your braking safety - if it's running low, your brakes might not stop as quickly or as powerfully as you need them to in an emergency situation. The truth is, if you didn't have any brake fluid in your hydraulic system, just your foot's force would not stop the car. But it is rare that you would run out of brake fluid. What happens more often is you run low on it and your car tells you with some symptoms such as an oily puddle under the car, "soft" and "squishy" brake pedal, and old brake pads. Note that your brake fluid can also go bad if it gets exposed to too much moisture in the air. 

Where is brake fluid located

Your brake fluid is located in brake lines which run all throughout your car from the master cylinder to each wheel. In old vehicles (think 1990s), brake lines become frayed and need to be replaced which is quite a big job. So make sure to inquire about the state of the brake lines if shopping vintage.

When thinking about replacing your brakes, whether you are installing everything new or just switching up the brake pads, make sure to double check your brake fluid is all good, and your brake lines are in good condition.