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4838[bmw e28] Brakes lockup, Some possible solutions

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  • Gil Thereault
    Nov 21, 2006
      Hello All,

      From my past experience, the high hard brake pedal issue is the brake accumulator. I have replaced mine twice in the past six years. You may have an issue with the regulator ?? from the noise you have described or it could have been due to the high temperature of the brake fluid in the regulator from the overheating of the rotor and caliper. I too have replaced the master cylinder as I also was experiencing the right front caliper locking up. I thought it was from the heat as well. I learned this after needless swapping out a good functional right front caliper. Do these things first (the easy things) then go further to the calipers and/ or the regulator.

      86 535i 192k

      John Forbey <jforbey@...> wrote:
      I don't know whether you will work on it yourself, but
      I say if it has'nt been driven in a while the calipers
      may have gotten what I call water spot that make them
      bind. Take the calipers off and they have screws that
      allow you to separate the halves. You can buy kits
      pretty easy, maybe price online dealers to find
      rebuild kits to replace the o-ring seals. There will
      be an expanding rubber cup that seals the piston and
      clasps around with wire clip. Clean the parts well
      and make sure no rust. Use silicon brake fluid to
      lubricate parts, seals before assy. This is just a
      start; but if it has'nt driven in while may be what
      needs to be done.
      John F. Forbey
      --- e34535 <e34535@...> wrote:

      > Hi, I am a new member and a BMW fan (tragic)from
      > Australia, I have
      > another e28 (aus delivered) among a stable of other
      > BMW models (1x e34
      > 535i manual,2x 3.0si, 2x 3.0L) and have just bought
      > at auction a UK
      > spec 1986 e28, the car is low mileage (44000miles
      > original with all
      > books and service). I was wondering if anyone has
      > had the problem this
      > car is exhibiting before (my high mileage rather
      > ragged aus spec e28
      > has never given me any brake trouble like this).
      > Being a UK spec the
      > ATE hydraulic booster is on the drivers side(RHS
      > above the exhaust
      > manifold) - the aus spec car has the ATE booster on
      > the LHS (US/Euro
      > Left hand drive style)
      > Problem: When I picked the car up I suspect it had
      > been not used very
      > regularly prior to its sale - brake discs showed no
      > overheating, on
      > driving it home I noticed that stuck in traffic the
      > brakes started to
      > squeal and bind - this got worse with a hard, high
      > brake pedal(no real
      > brake usage just stop start traffic) until the car
      > was labouring
      > against locked brakes, in 1st gear under full
      > throttle to just keep
      > moving. Bonnet up on roadside and many
      > expletives/+*?@#%$_BMWs later
      > I heard a series of metallic "clunks" from the area
      > of the brake
      > booster (this sound is easily heard inside the
      > cabin), at this point
      > the engine bay had started to cool down. I found
      > then that the brakes
      > had "let go" and the car could be driven again -
      > until you applied the
      > brakes (still some temperature in system)- lock up
      > again - car can
      > only be driven cold.
      > Long story made short - 1. Had brakes professionally
      > bled and took off
      > that night to drive home (550kms) at country speeds
      > (100km/h) - no
      > brake troubles at all! (cold night/cool engine
      > compartment) - thought
      > it fixed, but next day same problem with engine heat
      > again - bonnet
      > up/ cool down / "clunk" / brakes free again ???
      > Tested car by letting car heat up at idle for 15-20
      > minutes from cold
      > (good pedal/brakes OK when cold), car not driven, no
      > brake pedal use,
      > result:- rock hard brake pedal again and locked
      > brakes - placed trans
      > in drive but car would not move at idle, ran cold
      > water on the
      > hydraulic brake booster(not master cylinder)and
      > heard the light
      > "clunks" brakes slowly let go in unison with
      > "clunks" and car started
      > to move under its own power.
      > I am suspecting a faulty booster (or maybe
      > Bomb/pressure unit), there
      > is what appears to be a pressure valve on the return
      > line on booster
      > to the power steering reservoir - having never had
      > the need or
      > pleasure of dismantling a booster before I only
      > guessing what is
      > inside it.
      > Has anyone had this problem before? - any help
      > appreciated before a
      > costly "suck it and see" replacement program is
      > commenced. As I
      > mentioned before the car is in 1st class condition
      > for its 20 year
      > vintage other than this problem.
      > When things go wrong with an e28 they go WRONG! big
      > time

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