How Often Should I Refill My Brake Fluid?

CARS.COM — You deserve a gold star if you check your brake fluid on a regular basis, because it plays such a vital role in stopping your car. However, if you have to regularly replace lost fluid, it's likely there's a leak in your brake system that needs to be addressed — and pronto.

Related: How Can I Tell if I Need New Brakes?

Ideally, the brake fluid reservoir — typically mounted near the firewall on the driver's side of the vehicle — should always be at or near the full mark. Brake fluid is part of a closed hydraulic system in your vehicle, and under normal circumstances, the level in the reservoir should not change significantly.

As brake pads wear, though, the fluid level may go down a little. That's one sign that you need new brake pads. A soft or spongy brake pedal may also be caused by low brake fluid, which allows more air into the brake lines. The fluid provides the hydraulic force that causes the brake pads to be squeezed against discs or drums when you press the brake pedal, stopping the car.

If the brake fluid level goes down frequently or drops a lot in a short time, that means you have a leak somewhere in the brake system, such as in the brake lines going to each wheel, the master cylinder or in the hardware at one or more wheels. If that's the case, you need to make an appointment with a repair shop.

Topping off the fluid reservoir every week or two to replace lost brake fluid is only a stopgap measure, and further investigation by a mechanic is required to find out why the fluid level keeps dropping. Once you get a mechanic to pop the cap, the answer for what ails your vehicle ought to become clearer.

Speaking of fluids to keep an eye on, check out the video below for more on your car's essential fluids.'s Editorial department is your source for automotive news and reviews. In line with's long-standing ethics policy, editors and reviewers don't accept gifts or free trips from automakers. The Editorial department is independent of's advertising, sales and sponsored content departments.