CLutch Problems
 

I drive a 1996 Hyundai Elantra 1.6 GLs (J2). I replaced the clutch slave cylinder 2 days ago. Gears is changing fine, no problems. However, once the engin has run hot, and I slow down top stop, and I step on the clutch I have this huge knocking sound in the car, and the clutch pedal jumps up and down. This only happens in first or when slowing down and gearing from 3rd to 2nd. Further the gears is fine, no shuddering or struggling to get gear. I did blead the cylinder however I do not know whether there might still be air in this cylinder. Any ideas?