Have 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