Well, that piping diagram is the same one I was looking at last year when I
decided to replace the power servo unit (what you call the “brake cyl attached
to the power booster”) and I decided to replace the master cylinder at the same
time. Clearly, the new one could simply have malfunctioned also. It just
seems so bizarre when I think that the first one went for 25 years! I am still
a little suspicious of the PDWA which is not on your car. I know that it is
not working properly.
“John R. Walker” wrote:> Gene wrote: "About a year ago, I experienced a condition with my 74 O2S
fluid was being lost from the upper reservoir and was overflowing from the
top of the lower reservoir. Believing this to be a malfunction within the
power servo cylinder, I replaced it along with the master cylinder with
new parts. The problem went away.
Today, my brake fluid warning light went on and, upon checking, I learned
that again the upper reservoir was low and the lower reservoir was
overflowing from the top! It is hard to believe that the new servo unit
is malfunctioning in the same way that the old one did. Did I misdiagnose
this thing in the first place? But, if so, why did the problem go away
for a year? As far as I know, the front system and the rear system only
come together in the servo unit and the PDWA. Could that be the source of
Gene: The only place where the two reservoir “meet” is is in the brake cyl
attached to the power booster. looking at the piping layout in the Haynes
manual it would seem that you are forcing brake fluid to flow backwards into
the reservoir feeding directly into the lower cyl. How and why this is
happening is anyone’s guess, but I think that is the place to start looking.
FWIW, I bought a rebuilt slave and booster once and it failed about 6
months after it was installed.
Regards, John Walker
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