I have a 2003 Lancer es, about 6 months ago the slave cylinder pretty much fell apart. I did a complete clutch and slave cylinder replacement, all had been well until a few weeks ago when the pedal became a lil soft and was not disengaging the clutch fully, I thought maybe the flex line or something was leaking. I inspected everything from the reservoir to the master cylinder to the slave cylinder, all is good and dry, I bled the system for the hell of it and it worked great, for a few days then same problem. Bled it again, worked great for a few days, now it is to the point that is gets soft within a few minutes of bleeding.

There is no fluid leak anywhere, reservoir level never drops unless I bleed it and then I fill it back up.

Anyone know what may be going on here, I am thinking air is getting in somewhere, but how does it and not leak fluid?

Bad part is trans needs to come out again to change the slave cylinder

Any ideas are greatly appreciated!!