NigeEss
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| posted on 24/1/06 at 07:47 PM |
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BMW 525 E28 brake trouble
Any BMW experts out there ? I've got an odd problem with a 1985 E28 525.
This car has (IMHO) a very strange set up for the brakes. There's no servo so
instead the brakes are linked into the power steering.
Trouble started with the brakes binding, seemed to be the front calipers so stripped
and cleaned them.
When I tried to bleed them them I found the linkage to the pedal was seized as on the
first pump it stayed on the floor and very stiff to pull back up. So that's why the brakes
seemed to bind, the pedal was effectively being pressed constantly.
So freed that of and now the fun really begins. As the pedal is pressed to bleed the
caliper, the power steering resevoir backs up and overflows as the brake pedal travels down.
There appears to be no loss of brake fluid.
So the question is, is the master cylinger bu**ered ( my main suspicion) or do these systems
have a particular way of being bled, eg having to drain the steering first. Seems unlikely but
as I know tho thirds of f**k all about this system I thought I'd call for help.
One last thing, despite the steering fluid loss the brakes bled ok and are working fine.
[Edited on 24/1/06 by Nige_S]
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mookaloid
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| posted on 24/1/06 at 08:02 PM |
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Sounds scary to me. Remind me not to get one of those for my next motor
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ed_crouch
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| posted on 25/1/06 at 02:03 AM |
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My family have worked on a few E28s.
You may (or may not) remember a diamond black M535i (C378VAB) which started life as just that. We put an E34 3.6litre M5 engine and gearbox in it.
That was us! If you were in the BMW car club about 8 years ago you may remember it.
Anyway: the E28s have power assisted brakes courtesy of the PAS system. You have a hydraulic pressure regulator under the bonnet towards the back of
the engine bay on the passenger side, with a metal sphere underneath it about 4 - 5 inches in diameter. The sphere is a pressure reservoir, with a
membrane across it and nitrogen behind the membrane. I remember that both these components used to go wrong. The regulator (about the size and shape
of a fist) was heiffing expensive, and the sphere was about 40 quid.
Maybe the regulator is allowing fluid from the pressure circuit back into the PAS fluid tank?
Pictures here:
http://www.bmwe34.net/E28/Repairs/Accumulator.htm
Ed.
I-iii-iii-iii-ts ME!
Hurrah.
www.wings-and-wheels.net
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rusty nuts
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| posted on 25/1/06 at 08:45 AM |
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Sounds a bit like the Citroen system where everything works from the pump . Just a thought , have you tried bleeding the brakes with the engine
running?
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NigeEss
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| posted on 26/1/06 at 12:42 AM |
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quote:
Originally posted by rusty nuts
Sounds a bit like the Citroen system where everything works from the pump . Just a thought , have you tried bleeding the brakes with the engine
running?
Yep, tried that one, no difference.
Thanks to all who have replied both in the forum and especially SimonH who U2me'd info, but I'm wimping out
on the job. The guy can take it to a specialist and I'll make easier cash with straight forward jobs.
Shame to admit defeat though 
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