Brake Fluid Contamination Causing Problems

Master cylinder cap of contaminated brake system

This article is about a car I’ve been waiting to work on. The problem with this particular vehicle is that it came in the shop with a very odd problem, as described by the customer. She would say that her vehicle would just come to a stop and die out after driving it a short while. This seemed very strange, and I’ve never really heard a complaint about a vehicle the way she described. Scanning the car revealed no codes and no problems with any of the electrical components. I drove the car a few miles and did not experience any type of problem like she was having. The service writer even drove the car, but never got it to act up.

After talking with the customer again, and telling her we could not get the car to die out, she wanted us to keep trying and figure out exactly what it was. This didn’t seem like it was going to be any fun trying to diagnose this car. When a vehicle isn’t doing what the customer says it’s doing, it’s always a hard fought battle to try and solve the problem. The next day, I decided to take the car on another test drive to see if anything would happen. It was extremely hot outside and just plain uncomfortable, but luckily I think that ended up helping me. I got the car about a mile from the shop and I noticed what seemed to be a dragging sensation. It was like the car was being held back and not going like it should. I turned off the main road and headed down a strip of road that we use for test drives. The problem was getting worse and worse as I drove.

Car Won’t Stop

I thought to myself that it sure seemed like the brakes were being applied as I was driving. The pedal felt normal at the time, but the car was slowing like the brakes were on. I had a thought that maybe there was some contamination in the brake system that was getting worse as the temp went up from the brakes and hot weather. I popped the hood, removed the brake fluid reservoir cap and low and behold I saw the problem. The rubber gasket in the cap looked an over-inflated version of the regular one. I knew immediately there was contamination of some sort.

This explained the slowing down of the car, and although it never died out, I was sure I found the problem. In fact, I barely made it back to the shop because the brakes were actually to the point of locking up as I was pulling in my bay. What was happening is that as I drove the car, and with the hotter weather that day, the contaminated brake fluid was expanding and actually applying the brakes without having a foot on the pedal at all.

When another fluid, other than brake fluid, is added to the brake system, the two fluids mix and a detrimental act begins to occur in the system. Anything that has rubber in the brake system, such as the brake hoses, calipers, wheel cylinders, reservoir cap, ABS unit, master cylinder, proportioning valves, etc….all become junk. There is absolutely no way to repair or recover from this without replacing every single component that has rubber in it. The contaminated fluid needs to be flushed out of the steel lines with fresh brake fluid, and then the entire system bled of air.

Brake Repair

All this is very labor intensive, along with a high expense for all the required parts. This particular car’s repair bill will be a little over $2,000. That’s quite a bit for the mistake of adding some other fluid to the brake system!!  So please pay attention to what you add to the brake system. It will only take a small amount of any other like trans fluid, power steering fluid, coolant, and oil to set you on your way of having a large repair bill. Use ONLY approved brake fluid to top off or flush your brake system!

Below are two pictures where you can see how contamination expands the rubber of the brake fluid reservoir cap. Just imagine that happening to every other rubber seal, gasket, o-ring, and more to your entire brake system! The first picture is of the cap from the contaminated system, and the second picture is of a normal cap. You can see the difference!!

Cap of contaminated brake system


Normal cap of brake system

I have a 2002 Pontiac Sunfire that during braking on ice makes a grinding noise.

ProTech: That is probably the anti-lock brakes activating.

So that *** awful sound is normal?

Yes. You should also feel the vibration in the brake pedal as it is activating.

sure do…I also have recently gotten a popping and grinding when I am stopping andd turning the wheel as well as a lurching when I am braking.

Hard to diagnose noises over the internet since I can’t hear them, but you might want to get the brakes checked for wear and the suspension and steering components checked as well for the popping noise.

Hey I appreciate your help.

No problem at all, glad to help!