<VV> Brakes - where did the air come from?

[Doug Mackintosh]

Thanks to everyone who gave me suggestions for what
might be causing my brake problem (air in the system,
low pedal, apparent fluid transfer from one reservoir
to the other in the dual master cylinder). I've been
through enough problems to have learned to appreciate
any suggestions, and I have been proven wrong more
than once.  Here is a summary of the suggestions I
received, and my current guess at the likelihood it
caused our problems:

One suggestion was to equalize the fluid level then
pump the pedal up to 100 times to recreate the
transfer and possibly fail the MC.  We did equalize
the fluid levels (a couple of weeks ago) and pumped
the pedal well over 100 times in normal driving.  This
did not cause any noticeable fluid transfer or fail
the MC.

One suggestion that the symptoms are caused by brakes
out of adjustment.  This could be part of the problem
(but I am also getting air out of the system which
must have another cause).  We opened up the rear
brakes last weekend, and the adjusters appear to be
working.  We have not yet checked the front.  The
brakes do stop well, with no pulling to one side, so
I'm guessing it's not one stuck adjuster.  We will
check the front adjusters next chance.  

Several opinions that the MC should either be rebuilt
or replaced.  This seems likely as I cannot otherwise
explain the fluid level change.  I have ordered a
rebuild kit.

One suggestion was that the front brake adjusters are
not working, resulting in the fluid level dropping in
that chamber.  But in our case the low chamber was for
the rear brakes, and the over full chamber was for the
front brakes.  Our inspection of the rear brakes
indicates the rear adjusters were working.  The front
brake adjuster condition is unknown at this point.   
Some suggestions that the air was there all along,
possibly as a result of not bench bleeding the MC
before installation.  But we did bench bleed when we
installed it in 2000, and the brakes have worked great
since then, until a few weeks ago.  Also, we bled the
brakes a couple of weeks ago (got all the air out as
far as I could tell) then found more air last weekend.
 While it is possible I didn't really get all the air
out the first time, I think we did.

Incorrect brake pushrod adjustment was suggested.  But
I think that should be something that was either wrong
from 2000 or is OK.  Since the brakes worked fine for
several years, I'm putting this one down low on the
list.

My current plan is to rebuild the MC and check the
front brake adjusters and report back to the group.

Thanks again, this is a great group.  If you have new
ideas, pass them on!

-- Doug Mackintosh
  Corsa member since 1996
  Corsa/NC member since 1996,  Virtual Vairs member
  Corvair owner 1969-1971 and 1996-on


	
	
		
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