[DeTomaso] Clutch Help

John Buckman jb841 at cox.net
Wed Jun 23 12:15:41 EDT 2010


Tom,

Just to be clear, the only things that you changed were the clutch master cyl and the slave cyl.

The clutch was not removed or replaced.

The clutch arm on the ZF was not removed.

When you verified the length of the pushrods, did you change the length of either or both?
If so, longer or shorter and which pushrod(s)?

When you lengthened the slave pushrod, did you have to readjust the free play?

Do you know if there is a spring behind the slave piston?

When components are heated (such as driving 10 - 15 minutes), their dimensions change, 
and that can adversely affect a given situation.

Assuming that there is no air in the system, I suspect that the MC pushrod length is too short.

Another possibility is the bore of the MC that you installed.  When I was rebuilding my system,
I purchased a stock new replacement clutch MC.  It looked identical to my original.  I took it apart
and measured its bore and the bore of the original MC.  The new one's bore was .065" larger than
my old original's bore.  If I had used the new one (which I did not), it would have increased the pedal
effort slightly and also increased the throw on the slave cyl.

Not knowing which MC you started with and which you installed, the is a possibility that you went 
from larger bore to a smaller bore.  This would give you less throw on the slave cyl.

John




On Jun 22, 2010, at 8:24 PM, tmshinro at aol.com wrote:

> 
> 
> 
> I've exhausted my brain on this one so I'm sending out a call for help.
> 
> I replaced my clutch MC and slave.  I verified the pushrods were set per the book (MC pushrod at 2.95" and slave pushrod at 3.05").  I set the freeplay at 0.100".  I pushed almost 2 reservoirs of clutch fluid through the bleeder (no bubbles).  I ended up having to extend the slave pushrod about a turn and half so the gearbox wouldn't crunch while standstill shifting through the gears with the motor running.   See some space between the pressure plate and clutch disk (measured 0.018") and some smaller space between the clutch and flywheel (couldn't measure).  With the car in gear and the clutch depressed I can move the car by hand (no clutch drag).
> 
> Here's where it gets weird.   At the start of my test drive, everything is great.  All gears shift smoothly, clutch engages about half way up the pedal stroke. Drives like it is supposed to.   After I drive around for about 10 - 15 minutes, the clutch won't fully disengage at full stroke (gears won't engage without having to pump the pedal).  After limping back home and pulling into the garage in 2nd gear, I push the clutch in and it sounds like the clutch is dragging the engine down (again not fully disengaging).   
> 
> I've been struggling with this for over a week!    It is very frustrating because I haven't had any clutch problems for over 20 years.   All ideas and suggestions are welcome and desired.
> 
> Thanks,
> Tom 
> #5186
> 
> 
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