How to Check a Vehicle’s Brake Fluid

To check your brake fluid, perform the following steps as listed:

Clean the top of the reservoir carefully.

A small amount of dirt falling into the fluid can cause the internal seals of the master cylinder to fail over time. Your brakes will begin to lose effectiveness and ultimately fail completely.


Open the top of your brake fluid reservoir.

If you have the kind with a little plastic reservoir on top, just unscrew the cap of the reservoir. If you have a metal master cylinder that contains the reservoir, use a screwdriver to pull away the retaining clamp off the top.

Don’t leave the master cylinder uncovered or an open can of brake fluid sitting around for too long. Brake fluid soaks up moisture to keep it from settling in the hydraulic components and corroding them. If moist air gets to brake fluid for as little as 15 minutes, the fluid is ruined. So don’t dawdle, and keep the can tightly closed until you’re ready to use it.


Look to see where the fluid levels are, make sure that the brake fluid level is within half an inch or so off the top of the cap.

If the level isn’t high enough, add the proper brake fluid for your vehicle. If the brake fluid reservoir is empty when you check it, you may have to bleed the brake system (or top up and pray).


Check the color of your brake fluid.

Because brake fluid deteriorates with use, it should be replaced by a mechanic if it’s dark in color.

Have your brake fluid changed every two years. Doing so protects the hydraulic components from internal corrosion and premature brake failure.

Also keep the following points in mind as you check the brake system:

Brake fluid is toxic, so take any rags with more than just a couple of small spots of fluid on them and any partially used cans of fluid to a toxic waste center for disposal.


Don’t get brake fluid on anything that’s painted because brake fluid eats paint. If you spill any, wipe it up immediately and dispose of the rag in the proper fashion.


Don’t get grease or oil in your brake fluid, either one may ruin your hydraulic brake system.