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Discussion Starter · #1 ·
hey guys.. so here is my situation... Noticed a worn spot in my steel braided lines when i installed pads a month or 2 ago... Well had to slam on my brakes the other day and ended up popping that line where that spot was.. drove home carefully and popped the wheels off and found that was the problem.. so I replaced the line and bled them.. started the car up and brake pedal went to the floor.. Took off all 4 wheels and bled all 4 ... pedal gets hard until i start the car.. bam straight to the floor.. Hooked up a vaccum/suction to the rear right caliper bleeder and pulled air bubbles and fluid for literally hours.. All together ive gone thru like 5 bottles of fluid with absolutely ZERO progress .. not even a little better and no signs of air in the system getting less... just endless.. What in the hell is the problem here? Ive checked all my lines and fittings.. everythings tight.. ive read ppl with similiar problems replacing master cylinder and not solving the problem.. i heard maybe need to bleed the abs... But i mean how could i still be pulling SIGNIFICANT amounts of air out of the lines after all this? Even for a few hours with the key off and not touching the pedal i sucked air filled fluid out with no signs of progress what so ever.. even if i had a hole somewhere that somehow isnt leaking.. if i wasnt touching the pedal that whole time and was purely pumping fluid out from one spot there would be no way for air to be sucked in? im soo out of ideas please anyone with any input it is extremely appreciated.. thank you
btw- 1998 bmw 528i w/ big brake kit..rd sport/alcon calipers-porterfield pads-stoptech dot 4 fluid.
 

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2 possibilities
1 sucking air around the bleed nipple threads
2 sucking air past the master cylinder seals. If you pull a high enough vacuum on the system air will enter the master cylinder bypassing the seals.
By now you have probably filled the system including the ABS with air bubbles.

RonR
 

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Are you pulling large bubbles or little micro bubbles? Vac bleeders often pull air from around the threads of the bleeder nipple and it looks like your pulling continuous air. As you know, it souldnt take that much bleeding. But if your still not getting any pedal it seems like master cylinder issues, if it always goes to the floor after bleeding. Are you sure you are not sucking the reservoir dry during the bleed? And as mentioned, you dont want to go max vacum pressure during the bleed.

Ive gone from a vacum bleeder (Mighty Vac) to a pressure bleeder (Motive Products), and I like it much better.



.
 

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Discussion Starter · #4 ·
Well i actually bled it the old fashioned way.. Kept finding air.. Then used a oil extractor.. Just creates a suction by a hand pump then continues to pull.. I had the hose very tight around the nipple and even zip tied it tighter around it to be safe..
 

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Discussion Starter · #8 ·
Yeah originally I did it the 2man way.... I didn't push the pedal to the floor.. But it's possible after I busted the brake line it may have hit bottom.. I was thinking perhaps the master cylinder but then why the continous air.. Is there a way to test the master?
 

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Well i actually bled it the old fashioned way.. Kept finding air.. Then used a oil extractor.. Just creates a suction by a hand pump then continues to pull.. I had the hose very tight around the nipple and even zip tied it tighter around it to be safe..
The air leakage problem with vacuum bleeders is not usually the seal between the hose and the nipple; It is the loose fit of nipple threads to the mating bore in the caliper, especially if you open it too far. Anyway, it is sounding more like an MC problem.
 

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Discussion Starter · #12 ·
The air leakage problem with vacuum bleeders is not usually the seal between the hose and the nipple; It is the loose fit of nipple threads to the mating bore in the caliper, especially if you open it too far. Anyway, it is sounding more like an MC problem.
Okie that makes sense... I'm going to try to do the pressure method of bleeding... And see what happens.. If nothing changes I guess I'll have to change the master cylinder... Could it also be a brake booster? Key off pedal gets firm.. Engine running the pedal has zero pressure.. No visual signs of leaking anywhere
 

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Discussion Starter · #13 ·
MC Seal: if it leaks, it leaks INTERNALLY, you won't see any brake fluid coming out.
Tow the baby to the indy.
For a guy who does some of the best diy's I've seen.. Ur pretty quick and persistent to take it to the shop... I at least wana be able to say I did everything I could before giving up on it.. I've done way more complicated stuff than this before.. Just haven't had much issues with brakes on any of my bimmers.
 

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LOL,

Haha.....I was just worried you get deeper and deeper into problems.
The indy shop I mentioned is a very inexpensive and run by honest people.

Anyway, to test for possible bad MC Seal: fill the reservoir to Max.
Don't bleed, just press pedal, if it goes to the floor then the seal is bad.
 

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Discussion Starter · #15 ·
Haha.. Ok ill try that b4 i do the pressure bleed.. Thanks for the info! And if all else fails I'll hit up that shop u mentioned.. I'llreport back in a few hours! :)
Btw is that Mc check with the engine running or off?
 

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Discussion Starter · #17 ·
Engine off the pedal is super firm after a pump or 2...Engine on it goes limp.. Just pressure bled the entire system.. Used blue this time so i knew when the whole system was cleared.. All the air is out but same thing once i started the engine.. Pedal sank.. Does feel a bit better.. But still something wrong.. If i pump the pedal with the engine run it builds a little pressure... But if I wait a few seconds it goes super soft again... Mc?
 

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Discussion Starter · #19 ·
Yahh.. No fluid on floor.. No visible leaks..I saw something that said if the pedal is stiff when keys off the master cylinder is good.. Any thoughts on that? Could there possibly still be like a huge air bubble trapped in the lines somewhere? Even with the thorough pressure bleed I did?
 

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Discussion Starter · #20 ·
Or (which is extremelyy likely) there is air trapped in the ABS as mentioned above.. Hey CN90 i saw in an old post you briefly went over how to manually vent the abs by having someone push the correct 3 to the correct caliper.. Anywhere or way you know of to figure out which ones go to which caliper?
 
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