Do you hear it while driving or when idling or both? JUST when pressing the clutch? How about just reeving the engine? Engaging/Disengaging the clutch would put stress on the engine thus creating exhaust, that would just be my assumption.. If the clutch disengages and engages and shifts fine, i don't see why it would be the fluid or tranny fluid...

Try a two man operation with one fiddling around inside the car and one pinpointing the noise, if not just try to get under the car and finding out what the noise is...

One way or another, it just sounds like something is loose..