Brake Adventures
I'd like to thank everybody for the good advice you all sent me on my brake
problem. I spent a good Saturday working on it, and I can say two things:
1) I still have no brakes :-(.
2) I know exactly what the problem is. :-)
Confusion was created by the fact that there were actually TWO problems:
1) A malfunctioning return valve in the master.
2) A leaking front brake hose.
This "return valve" is the only thing that keeps brake pressure from just
backing right up back into the reservoir. With a bad return valve, you have no
pressure. Period. Now, most NORMAL and REASONABLE master cylinders achieve
the same effect by having the feed hole near the front of the cylinder, so that
the piston pressure seal closes it off when you press on the brakes. But
Girling had to save money on the casting, and put in this Rube Goldberg machine
to keep the pressure in. It's almost enough to make me go buy a Toyota! ( Well,
not quite. Actually nowhere near. But it does bother me )
The valve depends on a three-legged spacer to hold it off its seat when
you're not pressing on the brake. This spacer is the cheapest, cheeziest pot
metal casting you ever saw. It looks like something produced by a third world
country for a child's toy. And they gradually disintegrate, there in the
cylinder, until the legs are no longer than the thickness of the rubber seal
that they're supposed to be holding up. When that happens, the valve will no
longer open. Then no fluid can get into the cylinder, so naturally, there's
nothing to pump OUT of it. This condition goes away when you pressurize the
reservoir with an EZ-bleed, since there is 20PSI or so, pushing the fluid in
past the valve. To get it working, I did two things:
1) Put in another spacer, borrowed from Dick Nyquist ( thanks, Dick! ).
Not much better than mine, but good enough to work.
2) Cleaned up the valve seat. This is actually just the back end of the
cylinder that you see at the bottom when you look in the open bore. You can't
reach it with a finger, even. How to clean it? I took a long bolt and ground
the head down, making it nice and smooth and flat. I also ground off around
the hexagon, leaving a bolt with a nice flat "button" on the end. Then I glued
a piece of 600-grit wet-or-dry sandpaper to the flattened head of the bolt.
Dropped this "valve-lapping tool" into the cylinder, and started lapping away,
removing the tool frequently to check my work, and keeping everything lubed and
clean with lots of water. Got a nice clean seat.
Then I put the cylinder together, and tested the valve by blowing into the
pressure outlet. Breath went right thru. Then when I pushed on the piston a
bit, closing the valve, it sealed right up. Good enough. Put the cylinder
into the car, bled it... Still no pedal. Got my wife out to pump. That's when
I noticed the fluid dripping from that old brake line. Guess I'll have to wait
'til the new ones come in. That should be any day now.
Also, it may seem like an anti-climax after all this work, but I just
ordered a new master cylinder from TRF. Even though I think I got the old one
working OK, there is a problem with the pressure outlet threads. Somebody had
apparently cross-threaded them. They were almost all gone, just barely enough
left to hold the pipe in the cylinder. When I thought about what would happen
if that connector popped out at the wrong moment, my hands reached for the
phone....
- Jerry
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