Like practically any other fluid your vehicle uses, brake fluid has a finite lifespan. In fact, it's usually recommended that you have your brake fluid changed every 30,000 miles in order to maintain your vehicle's optimal braking performance. Unfortunately, changing brake fluid is often seen as an intimidating job with a huge margin for expensive failure, which tends to put off many do-it-yourselfers.
Fortunately, changing your car's brake fluid isn't as difficult or intimidating as you'd think. All you have to do is follow these simple instructions:
Changing the Fluid in the Reservoir
Before you start changing your brake fluid, you'll want to make sure you're using the correct fluid for your vehicle. Check your vehicle owner's manual for the correct type of fluid your vehicle's brake system needs.
Once you have the correct brake fluid on hand, locate the master cylinder reservoir on the driver's side of the engine bay, closest to the engine bulkhead. Remove the reservoir cap and carefully remove the brake fluid with a turkey baster. Deposit the old brake fluid into a glass jar for later disposal. If there's enough space, you can mop up remaining bits of old fluid with a lint-free absorbent cloth.
Next, open your new bottle of brake fluid and pour it into the master cylinder. Fill the reservoir until the fluid level reaches the "full" fill mark. Afterwards, replace the reservoir cap and get ready to bleed the brake lines.
Bleeding the Brake Lines
Despite changing all of the brake fluid in the reservoir, there's still plenty of old fluid trapped in the brake lines. Bleeding the brake lines not only purges them of old fluid, but it also removes any air that was accidentally trapped within the lines.
Bleeding the brakes is normally a two-person job – you'll need someone to press the brake pedal as you drain the fluid into a glass container. In some cases, you may need to have the wheels off for better access to the brakes:
- Make sure the fluid in the master cylinder reservoir is up to the fill mark. Afterwards, replace the cap on the reservoir.
- Starting at the rear wheels, locate the bleed valve at the back of the brake cylinder or caliper. Fit one end of some plastic tubing of the appropriate diameter over the valve. Place the other end in the glass jar.
- Slowly crack open the bleed valve, but only enough to remove the fluid when the brake pedal is pressed. Don't let the fluid trickle out on its own. It's best to use a bleeder wrench to open the valve, as it'll prevent stripping or other damage to the screw.
- Have your partner press the brake pedal. Make sure your partner doesn't allow the brake pedal to hit the floor while pressing the brake pedal. Placing a 1-inch by 4-inch block of wood underneath the pedal can prevent this from happening.
- Your partner should continue to pump the brake pedal until there's no more air or old fluid in the brake line. Make sure you don't run the master cylinder reservoir dry while you're bleeding the brakes.
- Once the line is free of air pockets, tighten the bleed valve while your partner has the brake pedal depressed. Repeat the bleeding process at each of the remaining wheels.
- When finished, top off the master cylinder reservoir.
You'll want to take a test drive to make sure the brake pedal remains firm and solid. Don't forget to dispose of your old brake fluid properly. Many auto garages and auto parts stores can help you dispose of your old fluid in an environmentally safe manner at little to no cost to you. If you're still unsure about doing this project on your own, contact a local auto shop that offers brake service.