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      08-11-2019, 07:49 AM   #1
DRiFT_645
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Spongy Brakes after Flush

Hey guys,
Got an issue that has me confused.

A month ago, I had my brakes flushed at an independent shop. Within a few days, i noticed the brakes feel spongy, and sometimes need to be pumped. This got worse.

I took the car back and they redid the entire procedure. Problem persisted.

Took the car to BMW. They flushed it again, found air in one front caliper and one rear. Brakes worked well for a couple days and the problem came back.

Took the car back to BMW. They said theyíll flush it again because air can sometimes be trapped. They also did a more intense bleed of the DSC. Charged an extra hour too. M technician test drove the car and said itís great

Within 5 minutes of picking up the car, I noticed the problem is still there, though not as bad as before. I have to push the brake down a lot further for them to work.

Common issue throughout is brake pressure decreases even when holding brake (car begins to roll).

BMW now suspects failing master. Wanted your opinions. How can all this (and a master) fail after a routine flush? Brakes were PERFECT prior to starting this process

Thx in advance.
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      08-11-2019, 12:41 PM   #2
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Can only think the indy did something wrong in the initial brake bleed,perhaps pushing the pedal too quickly and hard or it's just coincidence that the m/c is failing.If the car has a lot of miles then it's possible, it can happen.Alternitively the brake booster/diaphragm enclosure has an air leak which can cause those symptoms.Is there hissing when holding brake?
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      08-11-2019, 05:33 PM   #3
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No sounds when holding the brake.

Car has relatively low miles on it... 100,000km (62K miles).

I can't see how a flush would cause the master to fail... BMW dealer said if they use too much pressure... indie shop says they didn't pump the fluid in.

Indie shop is a good friend of mine, owns the same car himself and did the same procedure to his car 6 months ago with no issue.
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      08-11-2019, 05:56 PM   #4
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I'm sure the tech checked for leaks on each wheel and brake lines? Maybe it's a coincidence but master cylinder seals do go bad if you let air in.
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      08-11-2019, 07:16 PM   #5
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Thanks for the tips guys. Car goes back tomorrow. If they suggest the master, which I suspect they will based on our conversation on Friday, I'll go ahead with it. I just hope the problem isn't still there after they replace it!
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      08-12-2019, 08:06 AM   #6
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A strange one for sure, but things do happen.

I plan to flush mine in the next few weeks. Keep us posted!
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      08-14-2019, 10:46 AM   #7
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How did you make out? Usually if you hold steady pressure on the brake pedal and the pedal drifts to the floor it could be a bad master cylinder. If you do the same and it only compresses some, it could be air in the lines.

Really strange how it started right after the flush. I doubt the master was damaged during the flush. Either there's a bleeder leaking allowing fluid /air transfer past it or there's still air in the lines. If they got air in the lines it could be trapped in the DSC even though I know you said they did that. ITSA has a whole procedure to do each caliper at a time, it flushes one line at a time while activating the DSC/Abs pump.
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      08-14-2019, 09:17 PM   #8
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Itís an odd one for sure. Drove the car yesterday and today and the brakes behaved perfectly fine. Tech thinks it might have been air. Keeping an eye on it over the coming weeks but for now, somehow itís returned to normal.
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