How to Check Brake Fluid at Home

These lights don't have to mean a trip to the mechanic if you know how to do some simple maintenance on your own. RMAX / Getty Images

Brakes! They’re one of the most important safety features in any vehicle. But how to check brake fluid — now that’s a question every driver should know the answer to.

Understanding your car’s brake fluid level and condition can help you prevent bigger problems down the road (and trust us, it’s easier than you might think).

So, why should you learn how to check brake fluid? Because it’s essential for maintaining brake performance, especially as brake pads wear or if there's a brake fluid leak. Let’s open that hood, dive into the engine compartment and take a closer look at how this hydraulic magic works.

1. Locate the Brake Fluid Reservoir

Start by finding the brake master cylinder reservoir (also called the brake fluid reservoir), usually located near the back of the engine bay, close to the brake booster.

In most cars, it’s a translucent plastic container with clearly marked minimum and maximum lines. Older vehicles might have a metal reservoir mounted on the master cylinder with a removable cap or lid.

Always check your vehicle’s owner’s manual if you’re unsure. Once you find the reservoir, perform a visual inspection of the fluid level. If the fluid is below the minimum mark, that’s an indication that you have low brake fluid.

2. Inspect the Brake Fluid Condition

When you check the brake fluid, it's not just about how much fluid is in there; it’s also about how it looks. Brake fluid should be a clear, light yellow color (sometimes light-colored green and pink). If it's dark, murky or has visible dirt, it may be contaminated fluid that could harm your brake system.

Because brake fluid absorbs moisture over time, high moisture content can reduce the boiling point, making brakes less effective. You can use test strips or an electronic tester to check the fluid's quality.

3. Add Brake Fluid (If Necessary)

If your fluid is low but clean, you can add brake fluid yourself. Brake fluids are rated by boiling temperature, with standards specified in the U.S. Department of Transportation (DOT) codes [source: US Gov Info].

Make sure to use the correct type specified in your owner’s manual — usually DOT 3, DOT 4 or DOT 5.1. Don’t mix types!

Before opening the brake fluid reservoir cap, clean the exterior to prevent debris from falling into the system. Slowly add fluid until it reaches the proper level, but don’t overfill. Replace the cap securely.

Know When to Replace or Inspect

If your fluid level drops frequently, you could lose brake fluid through a brake fluid leak, or your brake pads may be severely worn. Leaks in the brake lines, calipers or rear cylinders should be addressed immediately.

Also, if your brake pedal feels spongy or sinks to the floor, it’s time to get your brakes inspected. Beyond simply having low brake fluid, issues with the master cylinder or brake lines can be serious.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.