03-24-2023, 02:54 PM | #1 |
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Cannot Bleed Brakes
Hello, Im really hoping someone can help me out with a brake bleeding issue I'm having on my 435d coupe.
I have changed both rear calipers on my car and then proceeded to change the brake fluid too. (Should've never bothered changing the fluid ) After doing this I started to bleed the whole system using a pressure bleeder with no luck. The brake pedal is going 2/3rds of the way before there is any brake pressure so I've persisted with the problem. I continued to try bleeding the system using BMW ISTA and followed the brake bleeding procedure exactly, still with no luck. So I now thought perhaps there's a one off chance that the master cylinder has gone bad at this exact time or potentially damaged in the procedure. Ive continued to change the brake master cylinder hoping this would solve the problem. I then used BMW ISTA again and went through the brake bleeding routine 4 times in an attempt to get a pedal, still with no success. There's no signs of air getting into the system anywhere and no signs of the brake fluid reservoir going down so I'm not losing brake fluid. The pedal still goes 2/3rds of the way until there's a good pedal. Unless I hit the brake hard like and emergency stop or pump the pedal. After spending hours trying to solve the problem, I'm stuck and not sure where to go from here. I don't fancy going to the stealership for them to charge me a fortune to change one part. Is there a very unlucky chance I've got another bad master cylinder? Or is there something I'm missing? Has anyone else ever experienced this issue and if so how did they solve it? Any help is much appreciated. |
03-24-2023, 03:34 PM | #2 |
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Get a helper and do it the old fashioned way. Have them hold the pedal down. Crack the bleeder screw; fluid should come out immediately, the pedal will go all the way down. Close the bleeder. Have your helper pump up the brake pedal. Crack open the screw again, and more fluid should come out. Repeat these steps until the fluid comes out clean. Once it does you can move onto the next caliper. A pressure bleeder does the same thing, replacing the helper with the pump.
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03-24-2023, 04:06 PM | #4 |
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you only need ISTA if you introduced air into the system, by disconnecting brake lines from calipers and not having the brake pedal depressed. this would introduce air into the ABS system that ISTA can help bleed properly. if you just did a simple fluid flush, a normal bleeding procedure would be enough to get it done.
EDIT: just saw that you did change your calipers. I was just watching this Mat Armstrong video 30 minutes ago and he had trouble bleeding his rebuilt M5, maybe you can follow the same method he uses?
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Last edited by toxik; 03-24-2023 at 04:29 PM.. |
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03-24-2023, 10:00 PM | #5 |
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I only say/ask this to rule it out: calipers installed upside down (on the incorrect side) will make bleeding pretty difficult. Is the bleeding screw on the top, above the piston(s)?
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