> have a 77 Spitfire. I was bleeding the brakes the other day after
> replacing a rear wheel cylinder, and when I was finished there was quite
> a puddle of brake fluid under/around the Pressure differential valve.
> I've had the car 1.5 years and have noticed some wetness there before,
> but after bleeding it was quite a lot. I've only occasionally had to
> add brake fluid and the brakes are fine with a good firm peddle. I
> checked the unions into and out of the valve and they seem ok. However,
> the connection for the brake warning light was practically dripping
> wet. Is this common? Is there a fix without replacing the entire
> valve? I've considered just bypassing the valve. It is my
> understanding it doesn't do anything but tell you that you have a brake
> pressure problem, which you have probably already figured out anyway.
I took mine all apart to admire it. There is a center rod which is
turned down in the center. An o ring seals it on each side, with the
center area being open to the atmosphere.
I haven't installed it yet, but I did observe several things, neither of
which I particularly liked. One is the o-ring. That's the only thing
sealing the brake line there. Get any damage to it (like dry rot) and
you've got a leak that will bleed through the center and out the
switch. The other thing I didn't like was that when you pushed the rod
all the way to an extreme position the turned down center section seemed
to go under the o-ring on the oposite side. Which seemes like a heck of
a way to ensure leakage and air entrainment upon attempting to bleed the
brakes with any force on the pedal.
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