Firstfives.org

[tcolt]

I don't think the e12s ever had those hydraulic brake boosters filled with ATF, but I know that someone here will have the answer and roadfly seems kinda dead?

My brake fluid is slowly dropping on one circuit. The ATF is also leaking from the hydraulic booster (1989 535i). When I unbolt the master cylinder from the booster ATF leaks out pretty quickly. Should it not leak out at all when these two are separated or or is the seal between the two bad? Also, there seems to be a second leak from the brake master, since the fluid level is dropping, but it is dropping in the most forward circuit, so that one wouldn't thing that a leaky master cylinder should be the culprit. Also, I replaced it with a new one only a few years ago. I can't tell that there is brake fluid coming from anywhere else and the level is now starting to drop quicker than it had been in recent weeks. Any ideas where my leaks are and how and where these two brake systems are sealed off to one another and to the outside?.... Brake pressure is fine when I top off the brake fluid.....

Thanks, Tom

[Mike W.]

Mye28.com is probably better than the fly, even though it's an E28 board.

But I do know E28s pretty well too. No, you should not have an ATF leak when you separate the master and the booster. 95% of the time the large O ring in the booster is the only problem, on E28s and E23's it's a $3 part once you find it, and some time and trouble to do the job. The brake master. Not likely, you should see the fluid if it's the problem, though ATF could be masking it. More likely it's from a wheel or even the clutch, I don't know E34s well enough to know the reservoir layout to know which side the clutch draws from, but the fluid's gotta be going somewhere. Jack it up, check all the calipers, pull the wheels and look. Could even be the line going to the clutch master.
_________________
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter

[tcolt]

Mike. You know them better than I do and I've posted for 2 days on e28. It looks like they are pretty quiet over there.

So I have a leaking ATF booster seal, but I can't see where that seal would be in there. Is it behind the plastic insert? I can't find it in the parts diagram either: http://realoem.com/bmw/showparts.do?model=6724&mospid=47192&btnr=34_0207&hg=34&fg=25

Do you know where it is or do you know the part number and what has to come apart to replace that seal?

Also, would there be a seal between the booster and the MC as is used with the same MC and a vacuum booster? It looks like I have a separate leak in the brake MC, but it is not drawing from the clutch reservoir, but rather the forward reservoir which makes me even more surprised that is should be leaking out the rear seal.

Thanks, Tom

[tcolt]

Mike. A guy on the roadfly forum described to me how the booster easily comes apart and where the o-ring is on the plastic plunger that I thought was a sleeve insert. It doesn't look like the o-ring is available as a BMW part number? so I will probably match it from my assortment. One leak down, the second?.....

[Mike W.]

[tcolt]

Mike. Thanks much for your quick help. I'll do it today. I already had taken that plastic plunger out yesterday after being warned by Ron at the Roadfly site and I was just able to keep it together. Quite a bit of pressure on that spring. I think the parts are all pretty interchangeable between the e23, 24 , 28, 34..., maybe with the exception that the later cars had an aluminum booster housing instead of steel, but I'll find an o-ring. Thanks for the dimensions. That sounds like it could be right. Maybe 2mm instead of 3. I'll let you know....

[Mike W.]

http://www.mye28.com/viewtopic.php?t=101887

Follow the link for much, much, more.
_________________
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter