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Brake bleeding help

8K views 23 replies 13 participants last post by  herrubermensch 
#1 ·
I am in need of the group's help. My wintertime project of powder coating and rebuilding my calipers is quickly turning into my spring and heading into summer project!
Background 2000 M5 (3/2000) that was functioning fine. I decided I would do SS brake lines as long as I was rebuilding. Long story short, I had to cut one of the hard pipes (RF) and re-flange, but that required a disconnect from the ABS pump. Having not started or touched the brake pedal, I thought I could get away with a traditional brake bleed. I did a vacuum bleed (4 times each corner), then had my son help me with a pump and release bleed. Still no real brake pedal. I ordered the software from UK cables and it arrived last night. While I waited for the cables, I built a homemade pressure bleeder to use along with the cable.
This morning I hooked up the pressure bleeder, and ran INPA Old (could not figure out how on TIS). I could feel it cycle the ABS pump. I ran two cycles of "pump" while pressure bleeding each corner (in the right order). I went around the car twice like this. Pedal is there, but does not feel rock hard (with car running). I hate to put the wheels on and take it off of the jackstands if more needs to be done. My question is...does TIS do more than just activate the pump. Where does it live in TIS- does anyone have a flowchart to reach it? Is there anything else that anyone can see that I missed, or should try? I think I have done my due diligence and read everything that I could. At this point even the new Akebono pads are becoming suspect.
Thanks for any advice you can lend.
 
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#2 ·
I have had a couple of these where the pedal is just not that hard. I started seeing it in E34s 15 years ago. My guess is it has to do with pushing the caliper back. Now I open the bleed screw and push the caliper back. Once the cars I have seen do this once they do it every-time you push the caliper back without the screw opened. You can bleed these for hours and it does not seem to get much better. If you drive it and make the ABS activate it does get better and the pedal will get harder and harder. No explanation on how or why this works but it does seem to work. I don't think I have seen this issue on an E39M5 but I have had to deal with it on several E39s. I live in the country so it is easy for me to find a gravel road to work out the ABS.
 
#4 ·
I second Sailor24 (not that he needs any support).

I have had this exact problem on several E39 M5s and I have also come to the same conclusion that pushing the caliper pistons back without cracking a bleeder does something to mess up the ABS unit. I'm not sure if it has to do with the drain solenoids or what as I don't have any knowledge of the internal plumbing in the ABS unit. Several cycles of working the ABS unit with DIS cured it for all the cars I worked on.

E39 M5's have somewhat of an internet reputation for having soft brake pedals, but I think its really caused by shops doing brake jobs and not cracking bleeder screws on the calipers. People get their cars back with a soft-ish pedal and regular brake bleeding doesn't fix it so they assume that its just how it is and normalize the deviance.

The other thing I have seen in these cars is if the brake caliper dust boot fails or cracks and you get a bunch of gunk inside, when you push the pistons back it'll mess up the internal caliper seal. Oddly enough, in my example the crack wasn't noticeable unless you looked very closely, the caliper piston was not hard to push back and it didn't leak under full brake pressure. After exhausting other options, I tore the calipers down and saw where the seals were messed up.

Good luck in your troubleshooting.
 
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#5 ·
A side question....I bled the brakes and the clutch line the other day, using the pressure bleeder.
I managed to crack the bleeder nipples on all but the driver's side front caliper.
I soaked it in penetrating oil, but it's not getting loose easily. I am afraid to apply too much force out of fear of snapping it. I left it alone for now.

Any suggestions?
 
#6 ·
I have been chasing a solution to the same brake problem.

I have Brembo 4 piston BBK. When installed a few years ago, I loved the brakes more than anything else about the car.

I did a few HPDE events over the next year or two then started to notice the pedal wasn't what it had been. Bled brakes for hours, replaced pads with another brand, replaced pads with original Brembo pads, replaced master cylinder, bought pressure bleeder and cycled ABS using Autologic Blue Box while bleeding, smoked the motor and booster looking for vacuum leaks (none), replaced ABS pump and recently replaced ABS module.

The car had been to two different shops to see if I can get the original pedal feel back - no go.

I did Summit Point Main track a month ago and during first session on day one the pedal went soft. Car will stop but mushy pedal doesn't inspire confidence. Took the car to a third shop, then did Pocono Raceway two weeks ago. Pedal went soft on first session of first day. Everyone is now out braking me.

I bought a new brake booster and it arrived yesterday but haven't installed it yet (I get to bleed the brakes for the thousandth time - Wahoo!)

Note that the fluid level doesn't drop and the calipers and braided lines are bone dry (of course).

What's left? Rebuild the calipers?

For comparison, I have driven my other M5 with the same brakes and it will plant your face against the steering wheel if you aren't careful.

Subscribed for advice.
 
#9 ·
This is a real bugaboo for those of us who track our cars, Doug. You can tell instantly if the brakes are working as they should going 175 mph into Roller Coaster at VIR and needing to hit about 75 mph to take the turn. You have taken the main steps, including cycling ABS during bleeding. That cures a lot of these issues. But I find that pressure bleeders NEVER get the brake pedal as hard and as responsive as it needs to be. One HAS to use the "two person" method, one person banging on the caliper and releasing the bleed screw while another person presses the pedal. That is the ONLY method that has worked for me.

Best,

Peter
 
#8 ·
I think some of these old calipers need rebuilding every 80-100K. On the BB issue, I would suggest a Master Cyl after you have exhausted everything else. soft pedal issues are often traced back to a master that has an internal seal going away.

The only true test is a pressure gauge at each caliper to confirm what your butt and feet are feeling. There are a ton of tech articles on the tech forums on how to perform a brake pressure w/gauge testing. These tests can/may show that one or more ABS solenoids are not full open to allow full pressure at each wheel.

The second test is to confirm brake temps front rear left right after running med to hard. Record and see what you get vs others.

Helpful?
 
#10 ·
StephenVA - Hope you did well at the Concours d'Elegance. Sorry I didn't make it.
My mechanic insisted the original master cylinder was fine but I replaced it anyway because, you know, I know more about car repairs than a mechanic does. Or not. He was right and replacing the master cylinder made no difference.

Peter - Thanks for the support! I have been feeling like I am the only one who has ever experienced this and the brakes are fine. Until I hit the pedal at speed and no they are not! I will install the new vacuum booster and try your method. Do you cycle the ABS pump while bleeding the brakes and if so, how often? Each wheel? A couple of times per wheel? A couple of times per bleed screw? I have been waiting until the ABS cycle is complete before opening the bleed screw. Is this the correct method?

I have cancelled two events since Pocono because getting out braked sucks. Getting out braked every time sucks even more. Thanks for your help.
 
#11 · (Edited)
Most of the posters experiencing brake issues try 2-4 times per wheel cycling the abs unit, to pop out the last air pockets. Lots of fluid run through the lines, bang on each caliper, etc. air pockets on this abs block are a PITA.

On the Concourse results, I won my class and won best of Best of Marque for BMW. write up here...
http://www.m5board.com/vbulletin/us...che-marque-concours-d-elegance-vienna-va.html
 
#13 ·
I use a power bleeder and do each wheel 3x min, RR, LR, RF, LF as the master is closest to the LF caliper/wheel. It takes forever to flow clean fluid to the RR.
After all are complete. I do a pedal bleed as well as too many of these old BMWs have challenges in following bleeding procedures by themselves.
:wink
 
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