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Mario
03-04-2004, 03:47 AM
Greetings!

I have posed these questions on the E28 Board, and would like to get some idea from this Board. The problem is on my 1987 535isa, not my 1986 735i.

How do brake switches on the power flow regulator affect the system?

I have bled the system several times, and it still feels like the brakes are not "biting". I have to pump it a second time to get the feel that it works. I had to replace a new set of pads just to make sure it is not the pads that is causing the sympton.

Also, what does it indicate when the brake pedal does not get rock hard when trying to discharge the bomb or hydraulic accumulator

Any assistance is appreciated and thanks in advance.

Mario
1987 535isa
1986 735ia

demetk
03-04-2004, 09:45 AM
The old pump the brakes method with one end of a vacuum hose connected to the bleed nipple and the other immersed in a jar of brake fluid will work, but there is the real risk of ruining a used master cylinder by pumping past its normal range of travel. What you'll get is either a complete failure where the pedal goes to the floor or a failure of part of the circuit. In this case you'll never be able to bleed the system properly and the end result is mushy brakes because of the air, which is permanently trapped in the system. If you use your hand to push the pedal and listen carefully you can usually hear the air being forced past a leaking MC seal.

Before I built my own power bleeder, I ruined 2 MCs this way, although to their credit, each had over 150k miles before failure.

Please let us know what method you’re using.

demet

Mario
03-04-2004, 12:26 PM
Demet,

Thanks for the reply.

I have a vacuum bleeder. And according to a couple of members of this Board and the Bentley manual, the brake still has to be pumped to, I think, remove the air in the abs system?

I have bled the system a couple of times. But when I did the brake pumping while the vacuum bleeder is attached, the pedal got rock hard in about 5 or 6 pumps.

Mario

demetk
03-04-2004, 12:44 PM
pump the brakes 10-12 times BEFORE bleed screw is opened.

The vacuum bleeder is problematic because outside air tends to pass through the bleed screw threads and into the vacuum bleeder. This makes bleeding very inefficient. Some have used a little grease on the screw threads to provide a better seal.

Your best bet is to either build or buy a power bleeder.
demet

Mario
03-04-2004, 04:08 PM
Demet,

I have to apologize. I do have the power bleeder by Motive Products. I just couldn't remember the company name to look up if it's a vacuum bleeder or power bleeder.

I went back to old emails that I saved about bleeding brakes. At that time I was having problem with my 735i. A couple of those emails were from you.

Here are my final 2 questions...I hope.

When power bleeding the brake system, I have to pump the brakes at least 20 times BEFORE opening the bleeder screw AND about 12 more times AFTER the bleeder screw is opened?

What part of my brake system is maybe bad if my brake pedal will not get hard at all after pumping it at least 20 times?

Thanks and thanks to the Board/members for all the information/help that is shared.

Mario
1986 7351a
1987 535isa


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