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Ashaman074 03-31-2014 10:27 PM

Brake Bleeding Problem

I am really hoping someone can chime in with helpful information as I am about to go crazy out in my garage...

Over the weekend I replaced the pads on my X5 (2005 4.4). After that, all was going well, but I also wanted to change the fluid, so I opened the pass rear bleeder to drain while I was doing other projects. Well, of course I FORGOT and left it open allowing the reservoir to empty.

OK...so I figured I was in for a hassle now in terms of bleeding but I had no idea the frustration I had just unleashed upon myself. I have now been at this for hours trying to get brakes again.

Starting at the passenger's rear, I have worked my way around in sequence (pass rear, driver rear, pass front, driver front) a total of three times now.

As a first step, I opened the pass rear bleeder and let it drain forever, then followed with the others as listed. After all of this, I have nearly no pedal at all. At times I will get a mushy pedal, but after starting the car it will go to nearly nothing.

Aha! I thought...I must have air trapped in the ABS unit, I will cycle the unit using DIS and opening the bleeders! ...and still nothing.

I really don't know what could be going on at this point, I have run an entire 12 oz bottle of fluid through this blasted thing, and there has been no signs of air at the bleeders and no improvement in the pedal.

As it sits now, the thing is undrivable; it barely has enough braking force to keep itself from rolling away at idle!

FWIW I have done this job (and line replacement, master cylinders, etc, etc) I don't know how many times in the past (other vehicles) and I have never had an issue like this! Anyone have any further suggestions as to what could be going on? It is driving me nuts here - thanks!

upallnight 03-31-2014 10:57 PM

ABS pump is probably empty also. You are not going to bleed the system unless you have the correct software and knowledge on how to bleed the ABS pump.

Good Luck.

Ashaman074 04-01-2014 12:44 AM

I tried to do that, but I don't have a pressure bleeder - maybe that is the problem. Using DIS and just opening the bleeders and relying on gravity may not cut it...? I wasn't really clear on whether it was required or not. The instructions refer to using a pressure bleeder to flush the fluid; but once that is done I wasn't sure. Could be for the sake of time, could be it is necessary I suppose.

Actually I see many tales of woe here on the forums, and I find myself a bit irrationally hostile that something every toothless hillbilly has done since the dawn of the auto has turned into a fiasco that many professionals cannot sort out properly (including some BMW technicians it would seem.)

I am going to try the two man 'pump & hold' method again, but this time with the engine running, and I am going to try and find a pressure bleeder. Not overly optimistic on finding that last one locally, but you never know...most seem to operate on vacuum at the bleeder rather than pressure at the reservoir; and I am not sure it is quite as good. Or, if I can find a spare reservoir cap, that would be great too. Now, if only I didn't have to work tomorrow I might be able to get this sorted out! :)

Bargain Bucket 04-01-2014 02:05 AM

You are joking right? You are relying on gravity to pull the fluid through the system?

JCL 04-01-2014 02:35 AM

Sounds like it is going to be a hassle to fix.

You can't use gravity. You may have been able to do it with two people, but that wouldn't necessarily have flushed what was in the ABS controller. Once you got air in the ABS controller you were hooped.

Not a toothless hillbilly here, but I have worked on vehicles since the mid seventies, and have done brake jobs on vehicles from the twenties (a truck with mechanical linkages to the rear drum brakes) to current models. But I don't flush the fluid in my own BMW brakes. I don't need the hassle, and the dealer has trained personnel and the appropriate tooling to do it quickly and easily.

X5nHI 04-01-2014 03:04 AM

Try this poor mans version of reverse flush:

Fill a jar with new brake fluid.
Attach hose (shorter the better) from bleeder and submerge in the jar.
Remove cap from brake reservoir.
Pump pedal to force fluid out into the jar - and then suck fresh fluid in on the release.
Keep eye on reservoir level and repeat until no more bubbles appear.
Repeat each corner.
Then follow up with traditional pump/crack/bleed for any remaining trapped air bubbles.

If no work then tow to dealer.

LVP 04-01-2014 06:26 AM

I have chased crap brakes on my E36 for years and have tried everything to get air out of the system. You may have to bench bleed the master if it was run dry. The BMW procedure as per DIS is to pressure bleed the system, disconnect the pressure, run the bleed routine while pumping the pedal for each corner. Pressure bleed again, then no pressure bleeding once again. If you have the software it should walk you through it. I think this works to get small bubbles out. To try and evacuate an entire system or length of air, you may have your work cut out for you.

When I bleed (the track car), I switch fluid fluid colours so I can see it come out. If you are certain the fluid is flushed, then the air is in the master, ABS unit or the pump circuit. You may find that cracking the fittings at various points throughout will help bleed the air out in those sections. Always keep the pressure bleeder on and full when your doing this to avoid making it worse.

I haven't got into these brakes yet, so my experiences are only from years of messing with my E36 brakes, so take it with a grain of salt.

Acidphase 04-01-2014 08:06 AM

I'm not sure what others have suggested yet but basically sounds like you have air in the lines and the best way to fix it is with two people.

You need to do this with the car "off" and the abs disconnected by removing the abs relay and fuse.
Have your friend, girlfriend, wife, kidnapped neighbor whatever apply the brake inside while one caliber at a time open the bleeder to allow the air out until you have a clear stream of fluid bleeding out. (you'll now because you'll hear air and start to see foamy fluid then clear fluid)

Air is compressible this is the problem, brake fluid is not although it does start to boil at certain points sometimes moisture can get in the lines too which is why it's very important to bleed off air which has moisture in it.

mferek 04-01-2014 09:44 AM

The Bentley repair manual says that air can get trapped in the system (I think to the ABS module). Apparently, BMW's bleeder tool vibrates the system to loosen up this air, allowing it to escape. With out the vibration, the air won't move. So if any air gets into the system, the repair manual recommends you have BMW bleed the system. If no air gets in the system, you should be ok.

Since air has entered your system, I would say that you should just take it to a BMW shop, presuming you can get it there. If it's undriveable, maybe you can get them to come to you? Otherwise, towing is probably your only option.

RajB 04-01-2014 03:52 PM

I had this previously.

This is from my build thread on Xdrivers:

Unfortunately after quite some time of trying to bleed the brakes we had to give up as there was air trapped in the system which needed the pressure system and diagnostics laptop to be able to open the valves (unsure which but basically closes off the rear bias so you can not bleed them/use them. Fronts can still be bled as per normal). So in came our very own Jason from BWChiptune to sort it:






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