Is a Brake Fluid Flush a Scam?

brake fluid flushHave you ever had a mechanic tell you that you needed your brake fluid flushed? Is this a scam or good advice?

That’s exactly the question that a reader posed to me a while back after his mechanic told him that he should pay $89 for a brake fluid flushing on his truck with only 23,000 miles. The mechanic’s reason was that his fluid was dirty and would damage the anti-lock brakes. The truck owner thought the mechanic was just trying to get another $89 out of him, so he wrote to me for advice.

I do often warn readers that they are probably getting scammed or taken advantage of, but in this instance, it looks like the mechanic made a good call.

Moisture in the air gets into your car’s brake fluid over time just from condensation and can cause the internal parts of your braking system to rust. Dirt and debris also accumulates, and the brake fluid actually begins to break down as it is constantly heated and cooled.

Cars built before Anti-lock Braking Systems (ABS) were introduced weren’t as sensitive to these changes in brake fluid, but your modern brake components can be severely damaged by bad brake fluid. These repairs can be very expensive, so proper maintenance is important for your car and your wallet.

I have always recommended having your brake fluid flushed at about 30,000 miles or as part of any brake job. To perform a brake fluid flush, your mechanic will open the brake lines for each wheel. Leaving them open will cause the fluid to “gravity bleed” from the master cylinder. New brake fluid is poured into the master cylinder. The flush is complete when clean, clear brake fluid runs out at each wheel.

Now, don’t get this brake fluid flush confused with the process of bleeding the brakes. Any time your brake system is worked on, you run the risk of getting air bubbles trapped in the fluid lines. So the mechanic must bleed the brake lines to release any trapped air.

This bleeding process means just removing enough of the old fluid as needed to get out the air. Running enough new fluid through the braking system to flush out all of the old fluid and its debris is a much more time-consuming and fluid-consuming process.

One person “shade tree” brake bleeding video

On older cars, mechanics would pump and hold down the brake pedal with the brake lines open at each wheel to force the fluid through the system. This method is not advised for your new ABS, which is why I specified gravity bleed earlier. Applying pressure to your brake pedal when the brake lines are open can cause significant damage to your braking system by pushing debris into the master cylinder and other components.

Your mechanic should always use the gravity bleed method unless he has special vacuum-assisted equipment for brake bleeding and flushing. If you want to attempt a brake fluid flush yourself, use a reputable repair manual and follow the procedures carefully.

So how do you know if it is time for a brake fluid flush on your car? The method I trust the most is visual inspection. Simply remove the brake master cylinder cap and take a look. Your brake fluid should always be clear and have a yellow tint to it. If you see dark, colored, and/or dirty fluid, make arrangements to get that fluid replaced.

You can also buy special test strips to detect moisture in brake fluid if you have reason to be concerned about moisture content.

Austin Davis

About the Author:

Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."
  • Austin Davis

    Start with removing all 4 wheels and check wheel cylinders, brake hoses and metal brake line fittings and brake calipers for leaks. Then make your way to the brake master cylinder on the drivers side firewall under the hood and inspect for leaks there too. Sometimes a master cylinder can leak INTERNALLY and cause a spongy brake pedal and turn the red brake warning light on, although there are no external fluid leaks.

  • josephine ertell

    not sure where break fluid is leakin from know the light is on

  • Austin Davis

    You want to start with the farthest wheel away from the master cylinder, should be the right rear. Then the left rear then right front one at a time.

    It should be fine to bleed this system, just do not mash down on the brake pedal which pushes all the dirt and rust etc. into the master cylinder bore and can cause internal leaks.

    But honestly, unless you are doing brake pad replacement I don’t really see the need to do this at this point just for maintenance. I would wait until you do a brake job then do it.

  • Nathan

    Hi Austin, I have a quick question regarding gravity bleeding the brake system. I understand the process where you just allow the fluid to run out from the valves until you begin to see clean fluid coming out.

    My questions are:

    1-can you gravity bleed all 4 valves at the same time or do you have to do 1 at a time?

    2-if you have to gravity bleed each valve one at a time, does it matter which order you go in or is there a specific order you follow?

    3-finally, I have an old 1994 Mitsubishi 3000GT (non-turbo) with about 103K miles on it and I honestly don’t know if the brake system has ever been flushed or not. Would it be a bad idea to flush the system at this point since new fluid can possibly cause cracks/leaks in the old brake lines?

    Please let me know your thoughts and the best approach to my situation.

    Thank you in advance for all your help.

    -Nathan