I had my clutch replaced early last month and everything seemed to be working great until a few days ago. My clutch pedal is now intermittently sinking, seemingly only slightly around town and occasionally nearly to the floor on the highway, but even these identifiers are subject to it's caprice, as it will often work just fine for short periods. The pedal does not return by pumping however it does return fully when I pull the pedal back up.
I have not been losing brake fluid and no external leaks are apparent. The hoses appear to be in working condition and are not bulging. I took the car to the shop to have my mechanic verify this and to get another opinion. He said that this was unusual and after quite a bit of driving, he equivocally suggested that it was the clutch master cylinder, as, if it were the slave cylinder leaking internally, the clutch would be nonoperational.
So before I part with yet another 500 dollars or so on a potential fix I was hoping someone would share their wisdom and/or experiences with a problem like this so that I might be a bit less wavering in my decision. Thanks.

Cody