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
Guys I give up on the other boards. Need help with e28 brake
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.
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.
02 525ita. Wife's, aka grocery getter
02 530i. New to the fleet, 3 pedals.
03 QX4, AKA the Datsun. Finally got the 4WD vacationmoble to stop smoking.
07 Xterra. Still on the DL, a purchase from hell.
02 525ita. Wife's, aka grocery getter
02 530i. New to the fleet, 3 pedals.
03 QX4, AKA the Datsun. Finally got the 4WD vacationmoble to stop smoking.
07 Xterra. Still on the DL, a purchase from hell.
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?mod ... g=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
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?mod ... g=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
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?.....
Yes, that's the O ring, and no, I don't believe it is available separately. I think it's a 38X3, but don't go off that, not to mention I don't know if E34 is the same size as E28s. It's a messy job, but not particularly difficult, just be careful that plastic cup is under significant spring pressure and will go flying if you aren't careful, I was expecting it and it still took a trip on me. Occasionally one of the other O rings will be a problem, but like I said, 95%+ of the time it's just the big one.tcolt wrote: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.
02 525ita. Wife's, aka grocery getter
02 530i. New to the fleet, 3 pedals.
03 QX4, AKA the Datsun. Finally got the 4WD vacationmoble to stop smoking.
07 Xterra. Still on the DL, a purchase from hell.
02 525ita. Wife's, aka grocery getter
02 530i. New to the fleet, 3 pedals.
03 QX4, AKA the Datsun. Finally got the 4WD vacationmoble to stop smoking.
07 Xterra. Still on the DL, a purchase from hell.
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....