88 Chevy3500 w/4 speed manual L,1,2,3,R clutch

[Scoutsout]

Has any one ever encountered a problem with the clutch not having any hydraulic pressure after having driven on the freeway?, I've changed the clutch master cylinder and bled it, but the problem still exists ??, I have to pump it a few times before it actually builds pressure and it's fine. Driving in the city it's ok because you're constantly shifting. I'ts only when you drive on the freeway and exit that it loses pressure. Thanks.

[JohnC]

Is the clutch line too close to the exhaust pipe? Too much heat can boil the fluid.

If you pump it up but don't drive it, and come back several hours later, is it good or bad? (If bad, it's leaking...)

Oh, one more possibility. I'm not familiar with the construction in there, but hydraulics pushes the TO bearing out and the flex plate pushes it back. There has to be enough "friction" to keep the TO bearing from drifting farther from the flex plate fingers or you'll get the behavior you descrtibe as you pump the TO bearing back up to the flex plate.