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Oil in brake fluid

We took our 2005 Ford Freestyle to a shop we’d never been to before for an oil change. Three days later the brakes seized up. We had the car towed to different shop for repair. The mechanic at the second shop told us there was oil in the brake fluid. When I asked the first shop about whether they accidentally put oil in the brake fluid reservoir, they said they did not. Is three days about the amount of time that it would take for oil to cause the brake parts to swell and stop working?

That time interval sounds about right to me.

As to the original mechanic admitting (or even remembering) that he put motor oil into your brake master cylinder, getting an honest answer to that question is similar to the odds of getting an honest answer when you ask your fish monger, “Is the fish fresh?”.

You will never get an honest answer in either case.

How much oil?
Exactly what was the mode of failure?

Without doing a failure analysis to root cause of the actual failed part(s) it’s impossible to say.

I’d have to suggest that it stretches my imagination to envision someone accidently adding oil to a master cylinder reservoir rather than the engine. They’re totally different looking, in entirely different locations, attached to different assemblys, and clearly marked. Anything is possible, and I’m not going to second guess the guy that did the work, but this one seems a stretch.

I agree with VDCdriver and one has to wonder at least whether this oil in the brake fluid diagnosis is even correct.

Brakes seized up? Front? Rear? Both? Any symptoms up to the moment they seized? Towed in?

What I’ve seen when brake fluid is contaminated like this is hydraulic failure; meaning there was a loss of pedal, not seizure. Anything is possible though. In the auto world you can’t discount anything.

The mechanic who fixed the brakes said that the fluid looked like it had been recently “topped off” because the brake fluid reservoir was totally full. When the mechanic pulled the fluid and put some of it in a jar, about 5 inches was brake fluid and 1 inch floating on top was oil.

The failure was the brakes seizing up.

Exactly what part seized? A caliper?

Again, anything is possible and I won’t second guess him from here, but this one has an odd feel about it. Besides, while oil probably compresses differently than brake fluid and probably has different lubricating properties, I’m not even sure brake fluid would cause seizure. I don’t see a mechanism there to do so. Being considerably thicker than brake fluid it probably wouldn’t swell the seals.

Since our post were concurrent it does sound like the fluid is contaminated based on your last post. The mechanic did the right thing by saving that sample as it can be invaluable if push comes to shove on this issue.

Was this original shop a fast lube type of facility that advertises oil change with check and top off all of the fluids, etc.?

What kind of oil? The brake system is totally independant of any other system. The only way stuff gets in is via the cap in the reservoir for the master brake cylinder.

If the brake fluid has never been changed over the life of the car, perhaps the brake fluid separated due to age. Perhaps someone poured in motor oil, or power steering fluid into the brake reservoir when they “topped off” the fluids.

If the fluid in the system didn’t deteriorate due to age, then someone added the wrong fluid. The timing of the oil change coincides neatly with brakes failing 3 days later.

Therefore my “Sherlock Holmes” answer is the oil change person(s) at the shop messed this one up.

Lots of missing information, mis-information and outright BS posted here…

" Three days later the brakes seized up."
What does THAT mean?? Contaminated fluid usually makes the brakes turn to mush, the pedal dropping to the floor…

The ONLY way to determine if the fluid has actually been contaminated would be to send it out to an oil analysis lab. So far, everything posted here is just guess-work and opinions.

If you want to play games, take two small glass jars and pour an ounce or two of brake fluid in each of them. Then add an ounce or two of motor oil in one and power steering fluid in the other and shake them up. Observe the result. Do they mix and stay mixed? do they separate? If they separate, which fluid goes to the top and which to the bottom? Then go to a parts store and buy one wheel cylinder kit for any drum brake application. Drop a rubber cup into each jar. examine the cups every day and report back if/when they swell up and get all distorted and soft…

Then we can debate some FACTS instead of someones opinion and guesswork…