Brian,
I would guess one of the obvious, I know, duh! Either you do still have air
in the system or you are the unluckiest person alive with master cylinders.
I am leaning towards a lot of air in the system.
I have heard of replacing the rear transaxle calipers with spider calipers,
I've just not seen it. When the spider calipers are installed is the bleed
screw in a position to allow all the air out of the calipers? The transaxle
calipers go pretty much straight across the top don't they? And the spider
rears are pretty much at 3 and 9 o'clock aren't they? I'm 2100 miles from
my Alfetta and Spider so I can't go look.
I would remove the rear calipers and hang or hold them in a bleeder-up
position approximate to their normal position on a spider with a block of
wood or something to fill the space where the rotor goes and try to bleed
them that way and see if you get a pedal. With a block of wood or something
solid in the caliper you shouldn't have to remount them to get pedal feel.
From my limited experience every time I have had air in the system the pedal
would pump up and hold. If a quick stab gave a firm pedal and then holding
the pedal down with gentle steady pressure resulted in a change in the pedal
position then the master was no good.
Engine off, pump the pedal, does it pump up to a hard pedal and then while
holding it start the car. Does the pedal go to normal? booster is working.
For your vacuum drop check, there should be a check valve in line, is that
good? I don't know if or how that might affect the test.
If one of your previous master cylinders was bad did it leak into the
booster? If the booster is full of fluid I believe I remember that creating
a hard pedal with little braking, but could be wrong on that.
Good Luck,
Let us know what solves it.
Wayne
Date: Wed, 2 Jun 2010 08:21:15 -0700 (PDT)
From: Brian Shorey <[email protected]>
Subject: [alfa] Strange braking problem
Hey All,
We're having a strange braking problem with our LeMons car that has me
scratching my head. Here's the history and symptoms:
The car is a Verde, however we've removed the ABS and replaced it with a
stock non-ABS Milano system. Ran the car for three races, the brakes have
always worked fine, but felt a little mushy. Noticed that the fluid in
the reservoir had drained out over the winter, put 2 and 2 together and
made the blind (and apparently wrong) assumption that the MC was bad, so
replaced it with a new one, but didn't test.
Later, observed a leaking rear caliper, so did away with the rear calipers
and replace them with Spider rear calipers.
Bled the system a zillion times, including at every possible junction
coming out of the MC and bias block, we're confident that there is no air
in it, anywhere.
Now, we have decent brakes if we pump the pedal, however if we let it sit,
then press the pedal, it goes to the floor with some, but very little,
resistance.
With the car running and vacuum to the booster, everything is the same
except the pedal feels mushy..
Replaced the MC with a used one I had lying around (we'd already tossed
the original), and the symptoms are the exact same.
There are no hydraulic leaks in the system anywhere, we're quite confident
of that, and we're also confident we've got all the air out of the system.
Tried vacuum testing the booster, vacuum goes to 0 as soon as we press the
brake pedal (MityVac manual says it should drop about 6"). However, we
tried another booster I've got lying around and it did the same thing.
My question is this - is there anything internal to the booster that could
cause the problems we're observing? Every bit of experience I've got
tells me that if there is no air in the system, and no leaks, then a
sinking pedal is the MC. But we're on MC #3 now, and one of them was new.
Changing the booster is not fun in these cars, especially with a cage and
seat in there, so we'd rather not go that route unless we're sure.
Any input or advice will be greatly appreciated.
Thanks,
bs
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