installed new master and slave..still have air

I'm stumped! Last November, the wife's 2004 had developed a spongy clutch pedal. With a little diagnosis, I replaced both the clutch master cylinder and slave (air in the system with no external leaks). I bled the clutch as I normally would on any other car and all was good for a short while. Since then, I have warranty swapped the master cylinder and have the same issues as before but have to bleed the system every day and tons of air comes out. What an I doing wrong? All the line fittings are tight and I still don't have external leaks! Please help!

There is the case that one of the new parts is faulty. To me that sounds like the master.

I've replaced the master cylinder twice. It just doesn't seem to make sense to have the original and two aftermarket parts fail the same way.

it sounds like the seal on the shaft with release bearing might be letting air in?

does the 04 have the inspection plate for the clutch? pull it and look for signs of seepage.