Skip the auto shop - Our mechanics make house calls

How Does Brake Fluid Get Contaminated?

brake fluid contamination

For the most part, the braking system in a vehicle is closed, meaning bits of grit and grime can’t make their way in through any holes or gateways. In theory, that should mean the brake fluid inside the system will never get dirty and things like a brake fluid flush or replacement should be reserved for rare occasions when something serious is amiss. Unfortunately, your brake system doesn’t operate in a theoretical realm and moisture can make its way into the brake fluid through the hydraulic lines. As that moisture causes the fluid to chemically break down and the moisture begins to rust metal components in the system as a whole, you can end up with contaminated brake fluid.

If your vehicle has dirty brake fluid, it needs a brake flush, or a thorough cleansing to remove all unwanted particles and residual moisture before replacing the fluid with fresh, uncontaminated brake fluid. The problem lies in knowing when you have contaminated brake fluid. This is why many mechanics and manufacturers recommend performing a brake fluid flush every two years or 24,000 miles as a precautionary measure. There are circumstances, however, when you should consider a brake flush more frequently or may need one immediately, including:

  • Driving under heavy braking conditions: If, for example, you frequently tow a trailer or have a mountainous commute, you likely demand more of your brake system. With those increased demands, moisture will enter your brake fluid and begin wreaking havoc more quickly than usual.

  • Any time other work is performed on the brake system: There are two reasons why a brake fluid flush should be included when you have your brake shoes replaced or other brake system maintenance. First, it’s easier to do when you or a mechanic is already there. Secondly, your brake fluid is more vulnerable to accumulating moisture and other contaminants when other work occurs in that region of your vehicle.

  • Brake warning lights on your dash: When you see the ABS or Brake System light illuminate on your dash, don’t hesitate to have your brakes and brake fluid checked. This often means the fluid levels are low, which is likely caused by leaking brake lines, which also allows contaminants to enter into the dirty brake fluid.

  • Noticeable change in pedal pressure: Some people refer to this as a “spongy” feeling to the brakes, but it really refers to either the pedal depressing harder or more easily than usual. Both are bad signs and indicate you should have your brake system inspected, including checking for contaminated brake fluid, because fluid is likely leaking through the lines or master cylinder.

  • Pulling to one side while driving: If your car or truck noticeably pulls to one side as you drive, it could indicate a brake fluid leak, which would also mean the remaining fluid is contaminated from moisture and grit entering where the fluid escapes. Although this may be caused by other issues, it is important to rule out any problems with your brake system for safety purposes.

Contaminated brake fluid can have catastrophic consequences, which is why any issue with your braking system should not be taken lightly. If you suspect you have dirty brake fluid and may require a brake flush, don’t hesitate to call one of highly qualified technicians for a consultation.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P2159 OBD-II Trouble Code: Vehicle Speed Sensor B Range/Performance
Diagnostic Trouble Code (DTC): P2159 P2159 code definition Vehicle Speed Sensor B Range/Performance Related Trouble Codes: P2158: Vehicle Speed Sensor B P2160: Vehicle Speed Sensor B Circuit Low P2161:...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P0359 OBD-II Trouble Code: Ignition Coil I Primary/Secondary Circuit Malfunction
P0359 code definition The P0359 code indicates that a fault has been detected in one of the vehicle’s ignition coils, generally the number 9 coil. This code can also be associated...


Related questions

Q: Brake fluid leaks out

First off, I would avoid driving this vehicle until this problem resolved. The brakes have two hydraulic circuits in case one of them fails, but if one circuit is only braking for two wheels and the brake pedal will be...

Q: Grinding sound in reverse or neutral from park

Return the vehicle to the service facility; something could have been left loose, or maybe a faulty starter assembly was installed. I have heard similar complaints with different outcomes. When the vehicle is cold, check the power steering fluid...

Q: Brake lines need bleeding.

If the brakes need excessive pressure to stop the car then you could have an issue with the brake booster is not working or leaking vacuum. the brake pads and rotors could be glazed and would require excessive stopping force...