Strange noise from clutch slave cylinder 3.8

I just rebuilt the clutch master cyl and it seems fine…however.when I push down on the clutch pedal i hear a noise like a swooshing noise .from the slave cly.and not much movement of the TOB rod…i took it apart and cannot see anything wrong…its pretty simple…seal is good…piston seems to fit fine…any ideas?

Could it be that you have air in the lines that is bubbling through the fluid?

It sounds to me that you’re hearing the air pushing through the bleed hole in the filler cap.