06-14-2014, 09:42 PM | #1 |
Relic
Join Date: Oct 2003
Location: Bethesda, MD
Posts: 12,458
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WTF is wrong with VAG?!
So, due to clearance issues, I have been trying to retrofit an audi brake booster and master cylinder to the E30. This replaces that Porsche 924 booster that works, but doesn't provide enough travel for me to get into ABS. A little bit less than optimal with 321hp.
Fitment wise, this was easy. A little hard line bending and an adapter fitting and done. And, of course, a little bit of further modification of the intake manifold. Function wise, it's been an unmitigated disaster. At least I've finally figured out why: It seems that if you bottom out the brake pedal, you ruin the master cylinder. Yes, that's right. Ruin it. Apparently the correct technique for brake bleeding is to put a piece of 2x4 under the brake pedal in order to avoid this. What in the actual fuck? Edit: And to be clear, when I say ruin, I mean "not enough brake pressure to keep me from spinning a front wheel with one hand."
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2011 M3 2006 Sierra 2500HD 4WD LBZ/Allison 2004 X5 3.0i 6MT 1995 M3 S50B32 1990 325is 1989 M3 S54B32 Hers: 1989 325iX 1996 911 Turbo |
06-14-2014, 09:49 PM | #2 |
195
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Posts: 24,614
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How does it get ruined? What happens to it?
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06-14-2014, 09:53 PM | #3 |
lawn boy
Join Date: Oct 2003
Carmudgeonly Ride: e46m3, f25x3,C5 Z06, C4 Vette, 06 CTD Ram, and a trailer
Location: Maryland
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I learned this lesson the hard way many years ago with a Honda.
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06-14-2014, 10:07 PM | #4 |
Relic
Join Date: Oct 2003
Location: Bethesda, MD
Posts: 12,458
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Apparently the seals invert, and it ends up doing literally nothing.
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2011 M3 2006 Sierra 2500HD 4WD LBZ/Allison 2004 X5 3.0i 6MT 1995 M3 S50B32 1990 325is 1989 M3 S54B32 Hers: 1989 325iX 1996 911 Turbo |
06-14-2014, 10:16 PM | #5 |
Mugwump
Join Date: Oct 2003
Carmudgeonly Ride: E46 330i, Chevy Colorado, Tesla Model 3
Location: NY
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06-14-2014, 10:35 PM | #6 |
lawn boy
Join Date: Oct 2003
Carmudgeonly Ride: e46m3, f25x3,C5 Z06, C4 Vette, 06 CTD Ram, and a trailer
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I don't remember spending much time diagnosing the exact cause of failure, but I've been careful not to push the pedal all the way down when bleeding brakes ever since.
...I just don't think the cylinders are designed with that much pedal travel in mind. |
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