odd hiss, clutch master issues

[ben swann]

Huw,

Sean Shoemaker and I went through this ordeal a few months back.  If I
recall correctly, we finally were able to reverse bleed by forcing
fluid into the bleed port on the slave cylinder and back into the
reservior.  The method of conecting a hose to the brake and using the
brake to force fluid into the slave cyl bleed port did not work, mostly
because it kept blowing off the hose and messing things up.

I think somewhere in the successful part of the process, we needed to
depress the pedal, and let up very slowly as the pressure bleeder
forced fluid in.  Kept doing this pedal up, pedal down until no more
air could be seen.  I think several times, when the pedal was
depressed, we could see the air bubble rise slowly up the clear bleeder
tube ( no air pressure applied, and would wait 'til it got back in the
cup.  Finally got a nice hard cluth pedal and no more sucking to the
floor.

We used an el'cheapo bleeder consisting of a plastic cup with cap and a
line from bottom of the cup to take the fluid and used air pressure(15
PSI) for short bursts to force the fluid down so not to drain the fluid
and get air into the hose.  Had to keep refilling the cup.  Kinda
cludgy but worked - got the bleeder from Pep Boys I think.   Could have
taken the cap part off the nice pressure bleeder I started with and
just the hose, but it wasn't mine, so I didn't.

We had started doing the job with that nice pressure bleeder, but for
some reason it did not work this time like it did with no problem on
another 5kq.  The whole thing was a PITA and this simple bleed the
slave process that should have been 15 min. turned into a full day or
two.

Ben

[From: Huw Powell <audi at humanspeakers.com>
Reply-To: audi at humanspeakers.com
To: audifans <quattro at audifans.com>
Subject: odd hiss, clutch master issues

The story so far... patient is an 87.5 "special ed" coupe.  Needed
tranny replacement due to PO's error in clutch slave removal.

Did that the other night with Nate, installing a new release bearing and
clutch slave at the same time.  Didn't really bleed it right away, so of
course the clutch did not work yet.

A few days later, bled it fairly well with my horrible homemade pressure
bleeder, and got "some" pedal - if jabbed fast and released, the
pressure would overcome the over-center spring and return the pedal.  If
held down for any length of time or pressed slowly, it would stay down.
  SO I figured it couldn't hurt much to throw in a spare old master
cylinder from parts car I have.

After installing that one and bleeding it the same way, the pedal would
consistently return, so I took a short test drive.  The clutch would
only disengage at the very bottom of pedal travel, but worked for a bit.
  managed to upshift a few times, turn into a driveway and stop, back
up, back into 1st and 200 yards back home - but at the end of the test,
the pedal no longer released the clutch.

Now when I press the pedal, once I get past the over center half way
point, the pedal drops almost on its own, and I hear an odd "hiss" from
the general area of the master.  Anyone btheardt?  I don't mind throwing
in a new master if this just means I trashed an almost dead master.  I
promise I will even reinforce the firewall a bit!

Just curious if anyone has more than a theory, has actually heard this
before.  It's too messy under the hood to see any leaks of any kind,
though I will do some more observing with another set of feet on the
pedal, soon.

Thanks!
--
Huw Powell
http://www.humanspeakers.com/audi
http://www.humanthoughts.org/]