Sinking Clutch Pedal

I've had this myself, though not on a Pantera.
The cause of the trouble was the spring inside the master cylinder that is meant to return the piston to the start position. The spring had broken, so sometimes the piston returned and the clutch would work. Sometimes it stuck 'down' so that when I pushed the pedal it wasn't doing anything.
Dirt inside the master cylinder could also cause this, either by making the piston stick or by getting under the edge of the piston seal and letting the fluid pass it by.
Hope this helps.

Michael,

Sounds like your master has a bad piston cup and is internally bypassing. I had this happen to me when I rebuilt the internal hydraulic throwout (Quella's) to fix it's bad, leaking quad seal ring. With that fixed, I still had no clutch movement!!?? Pulled and rebuilt the CNC master --- didn't LOOK bad --- and all has been fine since. You can rebuild MC and slave --- some say not worth the effort and of questionable results --- or buy aftermarket. Do NOT go with the internal hydraulic throw out, as it is a bear to adjust and requires full ZF removal to do so. Stainless long throw slave --- think Pantera East is cheapest on this --- would be best at the back end. Stock style and aftermarket --- CNC has a nice aluminum unit, call Quella --- masters are available from the vendors.
Good luck, Larry

Thanks Rapier and Larry,

It makes sense what you both say.

One more observation was that when the pedal was 'floppy' when depressed, the slave did not move. As the pedal was pumped, the slave would move little by little and when full pressure would return, the slave had it's full travel. Is this indicative of the MC being bad, as both of you suspect?

Larry,

Thanks for the benefit of your experience regarding the hydraulic throw out bearing. I wanted to find out more about it for possible future installation. I didn't think it would be that much trouble!

Michael

Yup. I had the same problem with my BRAKES (much scarier!). After rebuilding calipers, installing SS lines, I finally determined that the master was bypassing. Replaced it with Pantera East "later model" Ford unit with adapter. Now I have REAL (as good as you can get with stock calipers) brakes. Don't bother rebuilding the clutch master. Do it one shot, save yourself the aggravation. Maybe Marino can give you a break if you buy the master AND slave from him. While you're at it, if you still have that cheesy plastic line going to your slave, replace that with SS. It's $79 well spent. Me? Mine blew unexpectedly spewing brake fluid all over my FINISHED engine compartment!

Be sure you have a GOOD ground on your engine/trans. I went with the stainless hose to the slave and it tried to use it for the ground which blew a hole in the clutch line and left me without a clutch. I have added a ground from the engine to the bolt where the crossmember bolts up.

Hi Michael, this happened to me last fall and what we did was change the seals in the slave make sure the cylinder is smooth inside and the rubbers are ok works fine now. During the winter we rebuilt the master cylinder just to be safe.

I doubt that this is your problem, but I had a crazy clutch years back. Sitting in traffic on warm days my clutch would fall to the floor. After going through everything else, I finally discovered that it was caused by excessive engine heat evaporating the hydraulic fluid and creating air poeckets!

That makes since Deeb. I recently went through the problem of my intake manifold gasket going south and leaking oil into the intake ports. This casued my oil to run hot, which casue my motor to run hot. I recently checked my clutch fluid and it showed discoloration with what appears to be from getting hot. Fixed the instake problem. Flushed the clutch fluid and it's now back to normal fluid wise.

A "floppy" pedal fits with a sticky master cylinder. The exact thing happened on my Sunbeam Rapier (called "Alpine GT" in the USA). For most of the stroke of the clutch pedal all you are doing is pushing against a spring, only the last quarter inch of movement does anything. If you keep pumping, the master cylinder piston will sometimes gradually move back and the clutch will work, but not for long.
I say take the master apart to find out what's wrong, if it looks at all damaged or worn buy a new one. A new one is a better bet than a repair (I've been there a few times!).

Thanks Swen, Gary, Rob, David, Coz, and Rapier.

I'm going to address the master cylinder first, then the slave if need be. With all of the responses pointing in the same direction, I'm confident I'll knock this problem out quickly.

David, how did you ultimately resolve your fluid evaporation problem?

Michael

Guys,

I changed my clutch master cylinder and that did it. It was a bad MC. I've yet to take apart the old one, but I'll report my findings when I do.

You were ALL very helpful and pointed me right exactly where I should've been looking. This is what this BB is all about!

Michael