Skip the auto shop - Our mechanics make house calls

What Is Brake Fluid and What Does it Do?

what is brake fluid

Brake fluid, also known as hydraulic fluid, is responsible for moving the various components of your vehicle’s braking system. The fluid operates under high temperatures and high pressure and, without it, your car or truck would not be able to stop when you push the brake pedal inside your vehicle. Brake fluid is a non-compressible substance that lies within the brake lines, delivering the force created by your push on the brake pedal to each of the brake rotors on the four corners of your vehicle. This applies pressure to the wheels and ultimately slows or stops your movement. Here is a step-by-step and somewhat simplified look at how brake fluid works within a hydraulic brake system:

  • The driver depresses the brake pedal.

  • The pedal compresses a piston inside the brake caliper.

  • This compression increases the pressure inside the brake lines and sends the brake fluid into motion.

  • The pressure of the brake fluid then causes the brake rotors to squeeze down on brake pads, which then make contact with the wheels, slowing and eventually stopping wheel rotation and also the vehicle itself.

The types of brake fluid

While brake fluid function is relatively easy to understand, there is a wide variety of types to choose from, which may be confusing when it is time to replace the brake, or hydraulic fluid. The two chief types of brake fluid are glycol-based, which can be further divided by grade, and silicon-based fluids. Glycol-based brake fluids are typically used in vehicles with anti-lock brake systems (ABS) while silicone-based ones work only in cars and trucks without ABS technology. If a vehicle without anti-lock brakes has ever had a glycol-based brake fluid, you cannot switch to a silicone-based one because small amounts of glycol will remain behind and chemically compromise the integrity of the silicone. Glycol-based fluids are classified by a Department of Transportation (DOT) number up to 5.1, which indicates the boiling point of the fluid. Higher DOT numbers indicate better quality of hydraulic fluid that can withstand higher temperatures. To know what type of brake fluid is best for your vehicle, consult your owner’s manual or give one of our mechanics a call.

How often to change brake fluid

Over time, brake fluid can absorb moisture from the air, which will cause the fluid to degrade and not work properly. This is why it is important to periodically drain the oil fluid out and replace it with new fluid to ensure proper brake fluid function. Most mechanics suggest changing the fluid for brakes every one to two years, although every vehicle has different maintenance needs. Since the purpose of brake fluid is so integral to safety, check your owner’s manual for the recommended brake fluid changing schedule. If it is still unclear how often you should change out fluids or you suspect there is something amiss with your braking system, don’t put off calling a mechanic for help.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

Post a question and get free advice from our certified mechanics.

ASK A QUESTION

More related articles

How to Buy Fuel Treatments
Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine,...
How to Transfer a Car Title in Idaho
In order to prove ownership of a car, you must have the title. However, when a car is sold, given away or inherited, the title needs...
How to Get a Louisiana Driver's Permit
s licensing program. The first step in this program is to obtain...


Related questions

Q: How do you check the brake and clutch fluid?

Without fluid, your Brake system won’t work (or won’t work properly). That’s a serious safety concern. If your car is equipped with a manual transmission, the clutch fluid is supplied from the brake fluid reservoir. It’s important to keep an...

Q: Car lost all power after downshifting to go uphill

Hello! Although the Check Engine Light has been on before a new issue may have occurred, I would suggest hooking a scan tool up to the vehicle and retrieving the OBD2 codes. The problem you're having should almost certainly set...

Q: I have code c1223 in the car i have problem in the brake and the ABS light or VSC is not alarming in the dash.

Hi there. Unfortunately when you get this code on this vehicle it is due to an internal malfunction of the ABS unit. In some cases it can be a bad connection or a power supply problem so those should be...