what is going on with my clutch?

Master cylinder or slave cylinder might be going bad. Try bleeding it in case there is air in the line

 

Could also be vapor-locking, if the lines run near the exhaust manifold.

 

The Clutch Master or Slave Cylinder is on its last legs, replace before it leaves you stranded.

 

could be the throw out bearing went south or the adjustment was left loose and overlooked by all.i had mine adjusted once and they left it loose and it acted as you described.

 

First off, before we go with the master/slave cylinder notion, does your truck have a hydraulic clutch? I know the Volvos use them, I know the Kenworth T680 uses them, but this is the first I've heard of International using them.

 

Rub a little Viagra paste on the shaft and it will stiffen.

Seriously though, a clutch either works or it don't. I am curious what the mechanic said when it got to the shop on the hook and now it works.

 

"It felt like there was an air in the hydralic system or something"

I would bet the farm that it's a hydraulic clutch.

 

some systems have an air line running to the clutch hydralic unit to help with clutch return I would check that as a possibility. dont know what your driving style is but all you really need a clutch for is to reverse and get the thing in to your first gear.

 

Hi A Bug, I couldn't find any hydraulic parts listed for the Prostar, but I'm sure it's hydraulic. The truck seems pretty new to have a issue with the hydraulic system, like Slant6 says, either it works or it doesn't. I'd suspect it's either a pilot bearing, or more likely, a spring on the disc broke and hung the pressure plate up, and then let go. I went through a couple of clutches with my trucks, until I went with a disc with no springs(severe duty), problem solved. If your bell housing has an inspection plate, (old trucks did) remove and check for spring pieces. Either way, it's a pain. Good luck