[DeTomaso] final diagnosis of clutch problem (I think)

[Pantdino]

Well, I called CNC and they sent me a rebuild kit for the slave. Unfortunately, they now use O-rings and a different piston, so I called them and they sent me a new style piston (at no charge--kudos to them.)   So I reassembled everything and I still didn't really have convincing freeplay.  by looking at the clutch lever end of the rod and the internals of the slave, I suspected that the piston was too far into the bore and the spring was coil bound.  My guess was that as the clutch wore the lever moved forward until the piston was coil bound.
 
So I unbolted the lever on the clutch shaft and rotated it one spline counterclockwise, then reinstalled the slave and adjusted the rod for proper length, so I could feel the piston pushing against the return spring when I pushed the clutch lever forward and play between there and the point where it would be touching the t/o bearing.  

I see numbers between 1/32 and 1/10 inch in my notes and the workshop manual updates for the freeplay at the bolt and I'm still fiddling with the final adjustment, but I think the problem is solved. 

Thanks for your help. 

Jim. 


-----Original Message-----
From: Pantdino <pantdino at aol.com>
To: pantdino <pantdino at aol.com>; jb841 <jb841 at cox.net>; detomaso <detomaso at realbig.com>
Sent: Sun, May 13, 2012 6:02 pm
Subject: fourth and probably final update on clutch slave not compressing fully


I removed the slave and the clutch arm moves freely. Some black semisolid stuff and moisture was seen in the bore outside the piston, indicating the seals are going. I took the piston out of the bore using compressed air and the bore is perfect-- no corrosion. Same with metal portions of the piston. But there is some roughness of the edges of the seals.
Spring is intact and strong
 
I left the spring out and put the piston back in the bore by pressing it against a flat surface, but I can't get the piston to advance in the bore using a large Phillips screwdriver and pushing reasonably firmly.  With compressed air it shot out like from a cannon, so it was definitely in there pretty firmly.
 
So my perception is that the seals have swollen and were causing the piston to be stiff enough that the return spring could not move it.  I typically alternate Valvoline synthetic brake fluid with a fifty-fifty mix of that and ATE Ultra Blue, so I can see when the old fluid has gone thru.
 
The slave is a CNC aluminum one, anodized black. 
 
I'll have to check my old receipts for where I got it, but I'm thinking that when I got it I was told there were rebuild kits for it. 
 
Jim


-----Original Message-----
From: Pantdino <pantdino at aol.com>
To: pantdino <pantdino at aol.com>; jb841 <jb841 at cox.net>; detomaso <detomaso at realbig.com>
Sent: Sat, May 12, 2012 6:39 pm
Subject: third update on clutch slave not compressing fully


Well, cracking the bleed nipple open did not cause anything to move.  A little fluid came out, but I still couldn't push the slave piston up. Tapping w mallet was successful. Attaching the rather strong spring did not move the arm with the nipple open either.  Tiny pulses of fluid exiting the nipple were seen w each tap of the mallet.
 
So it's not an hydraulic problem with the master cylinder, it's a local binding issue. My current theory is that the slave piston is binding in the bore. Large hydraulic pressure from the clutch pedal depression is able to move the piston but the little return spring or my girly arm is not.
 
Any other theories?
 
 
 



 
-----Original Message-----
From: Pantdino <pantdino at aol.com>
To: jb841 <jb841 at cox.net>; detomaso <detomaso at realbig.com>
Sent: Sat, May 12, 2012 6:05 pm
Subject: Re: [DeTomaso] second update on clutch slave not compressing fully



hat occurred to me too. But since the system is under pressure I won't even 
eed the spring on.  I suspect that when I crack the bleed nipple loose the arm 
ill move and I'll have play again. With the spring on you can't evaluate for 
lay without taking it off again
Jim

-----Original Message-----
rom: John Buckman <jb841 at cox.net>
o: detomaso <detomaso at realbig.com>
ent: Sat, May 12, 2012 5:54 pm
ubject: [DeTomaso] second update on clutch slave not compressing fully

im,
ith the spring installed, try opening the slave's bleeder screw slightly to see 
f the slave retracts further
.e.  the stop bolt comes to rest at its stop).  Also check for free play at 
e master cylinder's pushrod.  The
shrod needs to be touching the retaining washer in the master cylinder.  You 
n't see the forward end 
 the pushrod, as it's inside the master cylinder.  You may have to pull the 
n from the pushrod's yoke to
eck.  
ohn
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