Sounds like the master cylinder is going. My 01. 5 went through 3 setups. The first was a line that popped out at the slave cyl. (a rolled pin backed out).
The second sounded just like yours - was intermittent for a couple of days - sometimes it would work and others not - then just went out completely. You could hear the fluid recirculating through the master cyl.
The last one started to feel 'funny', like the pedal had to go all the way to the floor before it would disengage, although it still worked fine. Since number 2 was under 12 months old, I took it back to Dodgeland in the NW and got a new setup under the parts warranty.
Good luck with yours.