Muffler Bearings


I have an 01 Montana van & I do @50K a year. I am very careful with service. I had the oil & trans fluid changed & they called & said my brake fluid had 300ppm of copper in it & needed to be flushed. I feel like I paid to have my muffler bearings greased or the air changed in my tires because it was stale. Did I? Or is this a valid repair. I dont want to say who it was because I dont want to make Firestone mad. Skippy


Brake fluid does get contaminated over time. Your van has over 50k miles and is 7-8 years old. If fluid has never been flushed before then it’s due.


it is better to drain and replace the filter than flushing it.


They were being honest with you, insofar as anyone really knows about the chemistry of brake fluid. Here’s how it works.

A chemical test strip made by Phoenix Systems called “Strip Dip” can reveal the condition of the corrosion inhibitors in the brake fluid. The chemicals react to the presence of copper in the fluid. The test strip changes color to reveal the condition of the fluid. When copper levels reach 100, it indicates the corrosion inhibitors are nearing the end of their life. If the copper level is 200 or higher, the corrosion inhibitors are worn out and the fluid needs to be changed.

So sayeth the chemists, Skippy. Who’s to contradict the experts?


I have never, ever heard of this. Thanks for the lesson, Steve.


Firestone is a scam place. However most vehicles specify periodic (mine 3yr/36 month) brake fluid change(not flush).


I never knew the “steel” lines were actually a copper alloy. I guess it makes sense to make them more malleable. Here’s link to some information-



The air in your tires gets “stale” very quickly; just try breathing some of it. However, it does not need to be changed, and muffflers do not have “bearings”; the have hanger(s) to keep them in place, and those MAY need replacing every now and then.

Your Firestone guys believe, like P.T. Barnum, that a sucker is born every minute.


C’mon, Doc. The OP was being sarcastic. Credit is due.

And in my village, the most reliable garage with the most knowledgeable and honest mechanics is the Firestone place. I bring them all of my basket cases, they always come through for me. Again, credit is due.


I used to work at a Firestone and we had to do the little brake fluid test strips on every car and record it on the paper work and if it turned purple (I think-- I don’t remember the specific color) we were supposed to recommend a brake flush. I think it would usually turn purple on about 75% of cars. I don’t recall anyone ever actually doing a brake fluid flush there, though, so I guess the front desk guy wasn’t selling them as hard as he was supposed to!

In my non-chain garage experience, usually some hydraulic part or other will fail before the brake fluid reaches the end of it’s useful life, at which point most of it gets changed just in the process or changing the part and bleeding the brakes.


I have never heard of the copper test but you did not waste all your money. Brake fluid is hygroscopic which means it absorbs water. I have seen brake lines rust through because of this so it’s a wash.


Thanx Guys !!! Skippy