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E28 (1982 - 1988)

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  #1  
Old 08-23-2011, 02:44 PM
Dani G Dani G is offline
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Location: Quebec
 
Join Date: Aug 2008
Posts: 3
Mein Auto: '84-528e,'86-533i,'96-850
Brake pedal slowly goes to floor

1986 535i

Your first thought will be Master cylinder. I replaced it with a used part off another car, still had the same issue, then bought a new one and it hasn't changed the problem. (300$ down the drain)

Symptoms:
With the car running the pedal slowly, with substantial force, creeps to the floor.

I do get braking power, but not 100%.

With the car off, they are hard.

I have pressure bled them several times. 2-3

The fluid level does not drop, even after putting the pedal to the floor 20 times. So no leaks.

We thought maybe there was a flex line that was flexing but I could not feel any bubbles while the pedal was pressed. I will attempt to pinch them with some Vise-Grips on the car side to double check.

Questions:

My manual does not specify a bleeding method for the MC. Is there one? Could this be the issue even after having pressure bled the system?

Could my Hydro boost be applying too much pressure to the MC and overcoming the seals? Otherwise I can't see how this system could affect it.

Any other thoughts?

I am desperate as I need this car on the road ASAP.
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  #2  
Old 08-24-2011, 07:04 AM
catso's Avatar
catso catso is offline
catso
Location: Chicago
 
Join Date: Dec 2009
Posts: 2,926
Mein Auto: 2000 323i, 1988 528e
That usually indicates air in the system. Bleed the brake fluid from each wheel with a clear piece of tubing into a jar so you can clearly see when the bubbles stop. You will probably have to go around the car a few times. Start with the RR, LR, RF and lastly LR. Leaving the bleed screws open overnight to "gravity bleed" the system might also be helpful.
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Last edited by catso; 08-24-2011 at 07:12 AM.
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  #3  
Old 06-25-2014, 08:27 PM
alichak alichak is offline
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Location: MAdison, WI
 
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Posts: 105
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Mein Auto: BMW X3 2004 2.5i
Quote:
Originally Posted by Dani G View Post
1986 535i

Your first thought will be Master cylinder. I replaced it with a used part off another car, still had the same issue, then bought a new one and it hasn't changed the problem. (300$ down the drain)

Symptoms:
With the car running the pedal slowly, with substantial force, creeps to the floor.

I do get braking power, but not 100%.

With the car off, they are hard.

I have pressure bled them several times. 2-3

The fluid level does not drop, even after putting the pedal to the floor 20 times. So no leaks.

We thought maybe there was a flex line that was flexing but I could not feel any bubbles while the pedal was pressed. I will attempt to pinch them with some Vise-Grips on the car side to double check.

Questions:

My manual does not specify a bleeding method for the MC. Is there one? Could this be the issue even after having pressure bled the system?

Could my Hydro boost be applying too much pressure to the MC and overcoming the seals? Otherwise I can't see how this system could affect it.

Any other thoughts?

I am desperate as I need this car on the road ASAP.

I have the exact same problem after replacing brake pad and rotor and calipers, needless to say after professionally done brake bleeding! I thought I had some air in the ABS system, so went to an indie to do a proper bleeding with ABS activation....which he did, but didn't fix my problem.

IF you figured out what was wrong, please let me know. I'm about to drain 300$ down the toilet and buy a new master cylinder!
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  #4  
Old 06-26-2014, 01:47 PM
south26 south26 is offline
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Location: Dayton, OH
 
Join Date: May 2009
Posts: 715
Mein Auto: 535i 1989
I have a good used brake master for 50 shipped.


Andy
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  #5  
Old 07-20-2014, 01:18 PM
alichak alichak is offline
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Location: MAdison, WI
 
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Mein Auto: BMW X3 2004 2.5i
Quote:
Originally Posted by south26 View Post
I have a good used brake master for 50 shipped.


Andy
thanks for letting me know. will be in touch if I figure out it is the problem.
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  #6  
Old 07-01-2014, 07:44 PM
BMWFatherFigure's Avatar
BMWFatherFigure BMWFatherFigure is offline
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Location: Perth, Western Australia
 
Join Date: Aug 2012
Posts: 2,144
Mein Auto: E23;E30;E38;E32;E34 +
Pedal creep can be an internal leak in the MC between the chambers. That would be my first thought. That will nott show any fluid loss. Bleeding the ABS unit is a bit of a 'black art'. I would consult a good brake specialist for that. Creep is not usually air in the system - that is just a 'spongy or springy' feel with consistant movement. It is not possible for the booster or servo to over presurise.
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