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5014Re: [bmw e28] Brakes lockup, Some possible solutions

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  • e34535
    Mar 7, 2007
      Hi guys found the problem with siezing brakes - it turns out that the
      master cylinder is cast iron on this model not aluminium, removed
      master cyl and warmed it up in oven and the cylinder siezes - could
      either be distortion in the body or the bore grabbing on the piston -
      cut a long story short - replaced master cyl with alloy version,
      rerouted the pipes to the new connection positions and no more siezing
      - wierd!

      --- In bmwe28@..., "e34535" <e34535@...> wrote:
      >
      > --- In bmwe28@..., Gil Thereault <giln1oiw2001@> wrote:
      > >Hi Gil,John and Steve Thanks for the posts guy - a little more
      > evidence for you.
      > I inspected car thoroughly before auction to check for signs that it
      > was not an original garaged 44000 miles vehicle - all points backed up
      > the claim, service books would indicate little use over the last
      > couple of years. Disc rotors showed NO signs of any heat effects at
      > all, at this time - drove/stopped (when cold) beautifully on auction
      > test drive. Problem raised its head in traffic after leaving the
      > auction house - when I got the car off the road all 4 discs were
      > smoking and blue. When the brakes "let go" on cooling, all 4 let go
      > together(so I am thinking what ever is doing it is affecting all 4
      > discs at once, and probably both brake circuits - (when these babies
      > lock on( this happens progressively not suddenly) its back to 1st gear
      > (auto), foot flat to the floor/maximum load on the motor/box to creep
      > along at walking pace. Obviously this no way to treat a lady, as
      > mentioned, if you then lift bonnet and wait maybe 10-15 minutes
      > cooling the engine bay down the brakes will slowly release (all 4). I
      > have had on one occassion, the brakes suddenly release (with a "clunk"
      > from the vicinity of the booster while I had my foot flat to the floor
      > against the brakes looking for a pull off spot (very interesting
      > effect - like stalling up on the drag strip and sliding your foot off
      > the brake pedal - BANG and we are away). I could maybe see problems
      > from boiling brake fluid/calipers siezing when hot/overheated
      > hydraulic fluid on the booster power side, BUT,and it is a big BUT, As
      > mentioned I have tested it on cold start ups, brakes fine (roll car by
      > hand, no binding, cold brakes/calipers/fluid (has had 2 brake bleeds
      > now)/cold discs etc., and by the time the car has reached operating
      > temp you cannot roll the car by hand , and in 15mins you cannot drive
      > off at all. Lift bonnet at this time and hose only the booster with
      > water and brakes will gradually let go (hosing the
      > accumulator/pressure block and the master cylinder do not have any
      > effect). Looks like it may be a surgical strike is called for
      > (disembowlment of booster for starters). Would a faulty accumulator
      > produce a hard high pedal all the time it is pressurised or be
      > affected by heat?
      >
      > This car is starting to look like a reinCARnation of an old girlfriend
      > - well kept, low mileage, great upholstery, tight suspension, but
      > temperamental,with a personality (suspect) all of its own - and puts
      > the brakes on hard just when your starting to enjoy it!
      > Kevin
      >
      > > 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.
      > >
      > > Gil
      > > 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
      > > jforbey@
      > > --- 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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