hydraulic clutch problems

I have a 2000 Hyundai Elantra, and I don't like double posting, but the Hyundai forum is dead slow, so I've turned to this forum in the hope someone recognizes this as a similar they might have had. What started off like a simple clutch is slipping - change the clutch, TOB and PP, - is no longer simple, as I have the same problem of a slipping clutch, only the parts are brand new now. Right after the new assembly was installed, it worked fine, but the clutch pedal seemed to grab awfully high up. Later in the day though it statred slipping again. To make a long story short, If I bleed the system, the next trip I make with the car, the clutch doesnt slip. Once you finish the trip the next time you use the car, the clutch starts slipping, and the next time you use it, it won't start again until you bleed the system( I think there is some type of corralation between the lock out switch on the clutch pedal doesn't get engaged for some reason unless the system is bled. I kind of think either the master cylinder or the slave cylinder (Hyundai calls that part something different) is shot, but if you think about it, if either of those parts were shot, you would be able to engage the clutch. The problem I have is it almost seems like I'm riding the clutch. Each time I bleed the system, I not replacing any fluid lost other than what was bled off. I don't seem to get any air out of it either. This is a puzzler. Any clues out there. Hyundai's service site does say check the pedal free play and I did make an adjustment but it didn't help.

if your pedal engagement is way high up then the clutch is barely grabbing. and when it heats up, will slip even more. if you cant adjust the pedal down any, i would check master cylinder operation.

sounds like a bad master cylinder