Public service info as to why you should flush your brake fluid

mrblaine

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I get lots of calls from shops and a few owners who fully ignore our warnings to flush the brake fluid BEFORE you push the pistons in to install new pads. Across the board it is always the same, we never have to do that on other vehicles. While I do not know why that is the case, I do know that the TJ collects crap in the piston bore at a very prodigious rate. This is 3 year old or so fluid in a TJ that the owner takes reasonably good care of, it has reasonably low miles. Along with what you can see, there were also ridges of built up hardened crap at the end of the piston stuck to the side walls that would have trapped the piston hard and at least tried to ruin a set of new pads.

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That is bad, I have gotten in the habit opening the bleeder before pushing the piston back in. I guess I may need to add another step.
 
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That is nuts.

What is the recommended frequency of flush @mrblaine? Once every 2 years, and in wet rainy regions even once a year?
 
I think he just stated to do it when you change the pads.

Sorry I wasn't clear. We warn folks to flush before they push the pistons in and get lots of disagreement as to why that is a caution. Last I looked it up, the service interval was every 2 years.

What I didn't know about was existence of the ridges of hardened material on the walls of the bore at the end of the piston. We had to chisel those out with a screwdriver and then wire brush them. Those being there would have locked the piston up and prevented the piston seal from doing its job of slightly retracting the piston when you let off the brake pedal.
 
That is bad, I have gotten in the habit opening the bleeder before pushing the piston back in. I guess I may need to add another step.

Worse than I expected and both sides were the same.

That does pose a dilemma for us now that we see what is likely to be in the bores. Probably not a bad idea to start telling folks to take them apart and clean them out. I've got access to some good rebuild kits for them, that may be a good option.
 
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Worse than I expected and both sides were the same.

That does pose a dilemma for us now that we see what is likely to be in the bores. Probably not a bad idea to start telling folks to take them apart and clean them out. I've got access to some good rebuild kits for them, that may be a good option.

That sounds like a great idea. I am having issues with a left BMB caliper locking up on rotor.
How do we go about getting a couple rebuild kits?
 
I have a power bleeder and I use it to flush the brake systems on all of my vehicles. On vehicles with ABS, pushing the pistons in when changing pads can result in crap getting into the ABS pump which will really cause headaches, hence the practice of opening the bleeders first. European cars have always recommended brake flushing every 2 years and I think that is now what the domestic manufacturers are recommending as well.
 
The last time I changed brake pads I went with BMB pads and followed the recommendation to flush out the old brake fluid. Brake performance was increased exponentially! Not sure how much of the improvement was due to the BMB pads and how much was due to the fresh fluid. IIRC, brake fluid readily absorbs air molcules, and when worked hard, that air can revert to bubbles that will cause spongy brake performance. That was the first time I ever flushed the brake system, so I may have been losing a lot of compression during hard braking prior to the flush.

I'm solidly in the "flush the fluid before every brake pad change" camp. Oh, and also solidly in the BMB brake pad camp!
 
I'm learning here so please excuse the stupid questions. How does flushing the fluid get those chunks out? And just for reference, I flush my fluid almost every year. After seeing that though, I'm inclined to buy new calipers next time!
 
How does flushing the fluid get those chunks out?

Don’t see how it would. I think Mr. Blaine was questioning that, too:

Worse than I expected and both sides were the same.

That does pose a dilemma for us now that we see what is likely to be in the bores. Probably not a bad idea to start telling folks to take them apart and clean them out. I've got access to some good rebuild kits for them, that may be a good option.
 
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