How to flush and replace your car’s brake fluid

And the reasons why you should
by Jason Tulio | Jun 15, 2019
PHOTO: Joel Messner/Freeimages

The parts of a car, by nature, are perishable. Sure, your car itself can last for decades if you take care of it properly, but you need to be diligent about replacing all the necessary parts to keep it running. This includes your brakes. Over time as you use your brakes to slow down your car, the pads, discs, and other parts which constantly rub against one another will eventually need to be swapped out as they wear down. These parts help to slow down your car and stop it from careening off the road, so you wouldn’t want them to suddenly stop working, right? On top of replacing the parts, the fluid which helps the braking system operate should also be replaced.

Just as you wouldn’t (or damn well shouldn’t) skip replacing your engine oil regularly, the brake fluid is the lifeblood of the braking system and likewise needs changing every so often. Brake fluid is used to transfer the force from your foot stepping on the brake pedal into pressure via the front and rear brakes to stop your car. As you can imagine, it’s subjected to very high temperatures as the brake parts heat up, especially in the wheel cylinders of drum brakes and the calipers on disc brakes. In order to work at optimum conditions, the fluid must maintain a certain amount of viscosity and a low level of compressibility as well. If it loses those qualities (or it’s been used for a certain amount of time), then it’s time to replace it.

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Okay, so now you know why it’s important to replace your brake fluid. Now, how do you go about it? Here’s what you’ll need:

  • Car jack
  • Jack stands
  • New brake fluid
  • Adjustable wrench
  • Hand-held vacuum pump (if you don’t have one, you can also use a turkey baster) 
  • Rubber hose
  • Plastic container
  • Safety gloves and protective eyewear
  • Rags
  • Rock or block of wood
  • An assistant

  1. Park your car on a safe and level surface. Set the car in gear and put a rock or a block of wood behind the tires to keep it from rolling.
  2. Make sure you wear your gloves and safety eyewear. 
  3. Open the hood and find the master cylinder containing the brake fluid. This is usually labeled.
  4. Open the master cylinder cap and place some rags around it to prevent spillage (brake fluid can ruin your car’s paint). Using the vacuum pump or baster, suck out all the old brake fluid.
  5. Refill the master cylinder up to the fill line with new brake fluid.
  6. The caliper you will bleed first will depend on your car’s manufacturer. Generally though, it’s the furthest caliper from the brake reservoir. So if the reservoir is in the engine bay on the passenger side, you would start with the driver’s side rear caliper first. Double-check with your manufacturer to be sure.
  7. Loosen the bolts on your wheels.
  8. Jack up the car and place it up on a set of jack stands.
  9. Remove the bolts and wheel of the caliper you’re going to bleed.
  10. Locate the bleeder valve and plug the hose over it. Place a container on the other end of the hose to catch the fluid.
  11. Have your assistant sit at the driver’s seat and pump the brakes about four or five times. They should notice the pedal getting stiffer.
  12. As they hold down the brake pedal, open up the bleeder valve and fluid will come out. 
  13. Repeat the process until fresh brake fluid comes out. The old fluid is normally darker, so you should notice the transition to the fresh, lighter fluid.
  14. Do the same steps for each of the other calipers. Make sure the brake fluid never gets below the minimum marker in the master cylinder. If this happens, you risk air getting into the system and you’ll have to start the flushing process all over again.
  15. Once all the calipers have been flushed, top up the brake fluid in the master cylinder back to the fill line. 
  16. Reattach your wheels and set the car back down the ground.
  17. Before driving, make sure your brake pedal has a solid feel to it when you press down. 

If you’re in doubt about this process, consult a mechanic.

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PHOTO: Joel Messner/Freeimages
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