clutch disfunction -- sticking MC piston?

[AlfaNeely@xxxxxxx]

      You guys have hit on exactly why I always bleed the clutch from 
underneath, especially brand new / dry systems.  When you push the clutch pedal down, 
the dry piston in the master cylinder often sticks down and returns only over 
time.  Bench bleeding the master before putting it on is OK, but then you 
drip fluid during the installation process.
       With the system installed and everything tightened, fill the brake 
fluid resevour.  Open the bleed on the slave and allow some fluid to run down to 
lubricate things.  Then push the clutch activation rod into the slave cylinder 
- push on the clutch fork.  Then close the bleeder and allow the spring in 
the slave to push the piston and the fork back to rest.  This draws fluid from 
the resevour into the system.  Repeat as necessary.  Follow up by pumping the 
clutch several times.  On the 105 / 115 Alfas, the system will self bleed a bit 
because the hydraulic lines all run up hill.  But you may have to work the 
pedal to move the fluid around and coax the bubbles to move uphill.
       This method has the added advantage of not requiring an assistant.  My 
wife's standard comment is that all I think she is good for is bleeding 
brakes / clutches.

Ciao,
Russ Neely
Oklahoma City



In a message dated 7/23/2003 12:13:01 PM Central Daylight Time, 
owner-alfa-digest@domain.elided writes:

> Date: Wed, 23 Jul 2003 09:54:16 -0500
> From: "Dan Hagrman" <dan@domain.elided>
> Subject: re: clutch disfunction -- sticking MC piston?
> 
> Modelle,
> I had (what I think is) the same thing happen when I put my engine in--the 
> master clutch spring was not pushing the master piston all the way back out; 
> it was sticking in the cylinder.  The clutch pedal returned to its normal 
> position because it's sprung too, but as you pushed the pedal very slowly (by 
> hand) you would feel it "engage" the piston partially down the stroke, at which 
> point fluid resistance would occur.  The piston and pedal are not 
> "attached"--if they were this would be much easier cause you could just pull up on the 
> pedal.  I found if you felt for engagement with the piston,  "punched" the 
> pedal down a half inch by flicking the pedal with your fingers and quickly 
> letting go, you could "work" the piston all the way back. Bleeding is a very long 
> process this way, since if the piston doesn't come back, it doesn't suck in 
> new fluid.  
> 
> Don't bottom out the pedal while bleeding since if the pedal is against the 
> firewall you can't "bump" out the piston again--when this happened I lightly 
> banged on the clutch master cylinder with a hammer a few dozen times so the 
> piston would come partially out again, allowing the "bump".  After several 
> dozen times of me "bumping" the piston out and pressing back in I finally got it 
> more or less kinda bled.  I'm driving it around in hopes use will loosen up 
> the piston, allowing better bleeding.  Note the piston comes back fine when 
> hydraulics are hooked up and the clutch pressure plate pushes fluid back into 
> the master cylinder, but the master piston would stick when the slave 
> cylinder bleeder screw was open (aka when bleeding).  My master clutch was pretty 
> new when I started the rebuild 3 years ago, but was left open (no fluid) during 
> the rebuild--bad idea in retrospect.
> Hope this helps and good luck,
> dan in kc, home of the former perpetual 2 liter rebuild 
> http://kcaroc.pcbs.net/techses/89rebuild0/thumbs.asp
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided