'01 clutch problem

[wanger]

I was driving on the interstate in my 2001 F-250 4x4 with 139k miles on it. I took an exit ramp and at the stop sign, I pushed the clutch in and pedal went all the way to floor with no resistance. The clutch remained engaged and I had to pull it out of gear while rolling to avoid an accident.

I reached down and lifted the clutch pedal back up and it popped right back to normal position. I was able to push the pedal back in, shift into gear and drive off. From that point on, the pedal/clutch has worked and no repeats of above experience however about half the time, the clutch pedal only returns about half way out to normal position. When this happens, with the slightest lifting effort, the pedal returns out.

In general, the return stroke of the pedal feels "wierd", not broken and not resistive, just "not right".

I parked the truck in the shop and haven't had a chance to look into anything other than to make sure that it had a full hydralic resivor.

Any ideas?

Mike