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Occasional brake problems
#1
We converted my car to front disc brakes. We removed the necessary parts from another car except for a new MC.

We have a good brake pedal, are confident we have no air, and we've tested the MC.

Randomly the pedal will go all the way to the floor. Thoughts?

Also, the brake pedal does not always rerun high enough to disengage the brake lights.
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#2
It sounds like an internal leak, also called internal by-pass, in the master cylinder to me. I've seen a few times, mostly with "rebuilt" master cylinders.
Chuck
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#3
c9zx;185099 Wrote:It sounds like an internal leak, also called internal by-pass, in the master cylinder to me. I've seen a few times, mostly with "rebuilt" master cylinders.
Chuck

YEP! +1

Kevin

1971 Mach 1
408C Stroker
C4 w/3,000 stall
8.8" Rear w/3.73's
Disc brakes all way around.

[Image: 28ivsix.png]




                                                                                             
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#4
c9zx;185099 Wrote:It sounds like an internal leak, also called internal by-pass, in the master cylinder to me. I've seen a few times, mostly with "rebuilt" master cylinders.
Chuck

Means that fluid from MC could move from one compartment to the other?
Or what?
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#5
Yes. This explains it reasonably well. http://books.google.com/books?id=H922It3...ng&f=false

Chuck
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#6
And again I would say, every day we learn.
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#7
We replaced the MC, bled the system again,have good pressure at each tire, and cannot find a leak. Any other thoughts?

Maybe wrong length on the pushrods?
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#8
I think c9zx has a valid solution to your issue. I have read also that the bore size has an effect on the pressure of the brake system. I would think that replacing the master cylinder with a new one would solve the issue. Check out the Master Power Brakes website here!

Master Power Brakes > P/B Master Cylinder FAQ's

http://www.mpbrakes.com/master-cylinders-faq

mustang7173
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#9
jeremycfr;187551 Wrote:We replaced the MC, bled the system again,have good pressure at each tire, and cannot find a leak. Any other thoughts?

Maybe wrong length on the pushrods?

Typically if the rod is too short you will have excessive pedal travel and if it is too long the brakes will drag. You should check it buy building a sheet metal gauge "block" as described in the Ford manual, chassis volume, 12-01-04. It is a precise adjustment. Chuck
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#10
jeremycfr;187551 Wrote:We replaced the MC, bled the system again,have good pressure at each tire, and cannot find a leak. Any other thoughts?

Maybe wrong length on the pushrods?

What did you do at the firewall?
The drum MC bolts on and I think has a spacer to hold the threaded blocks.
The disc booster has studs - no spacer but has a sheet metal plate.
It was years ago but I remember having to disassemble a converted car to swap plates as the pedal travel was off, brakes were very touchy.
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