For those joining the discussion late:
My TR-6 began experiencing a problem where both front brakes would
begin self-application after a short drive. In other words the brakes
would drag more and more as the pedal got firmer until the brakes were
locked. Letting the car sit for a while cleared the problem, which was
fairly intermittant.
And now the rest of the story:
Thanks to everyone for your suggestions and support. As you will see I
took the "scatter gun" approach to problem solving, so I will never be
able to prove who was right, though there is strong circumstantial
evidence (great... now I sound like Johnny Cochran)
I had suggestions that the flexible brake lines were collapsing, the
calipers were sticking, the master cylinder was sticking, and that the
brake servo was misadjusted/malfunctioning. I had already planned and
purchased parts for a brake overhaul, so I got started.
The caliper overhaul went well, nothing seemed amiss, but I had mostly
ruled out caliper sticking because both would have had to malfunction
at the same time. BTW, if anyone knows the trick to getting the metal
clip on the new style Girling boots I'd like to know. After a
frustrating 2 hours I reused the old boots which were in good shape.
I replaced the the flex hoses, also ruled out because of the
simultaneous malfunction theory, with teflon/stainless hoses. For some
reason all the nuts that hold the hoses to brackets were VERY hard to
remove, as if cross threaded. They were difficult going on, so I
discarded them and used new.
The MC had been overhauled just a couple years ago, but I removed it,
pumped clean fluid through it and checked its operation. This too
seemed good.
The vacuum servo looked OK, and Bentley wasn't any help in checking it,
but my trusty Autobook said that with a straight edge across the servo
there should be .011 to .016 inch clearance to the plunger. Mine
sticking out at least .030 past the straight edge! I was able to screw
in the end to be almost flush with the face and I filed it the rest of
the way. Does anyone have a theory as to why this plunger would grow
with age? Or how (if?) this could cause my problem?
Everything works great now, the pedal has much better feel with less
effort needed to stop. I should probably think about getting a new
servo though ;-)
Tom Gentry
Life is much shorter driving cars with bad brakes!
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