Bubbles Emerge in Clutch line Regardless

[vmartin350]

My son stated that he was driving and suddenly the clutch felt spongy and didn't pop pass the spring assist as fast as normal. I read the forum stuff and got and used a power bleeder. Got all the bubbles out and but no difference. I've gone through about 20 16 ounce cups of DOT4. No sign of fluid leakage (plus output=input exactly every time), but even after all that air somehow is being introduced into the system over and over again because bubbles will come out. No idea but now I figure it's time to replace the Master or Slave Cylinder, but which one is most likely the culprit? What can introduce air when I have it totally closed (full reservoir and submerged bleed output hose). Tried bleed w/ clutch up. Tried w/clutch to the ground, Tried with power bleed + pumping in coordination with opening and closing bleeder valve. All with same results (except clutch up - that results in no clutch pressure). Any ideas/experience would be much appreciated.

[vmartin350]

Any ideas? (just hoping to get some help before I turn it into the Porsche mechanic).

[Mark_T]

Clutch depressed is the correct bleeding position. Also, the output for the clutch line is the one that comes off the side of the reservoir, whereas the brakes are fed from the bottom output. You do have the side output below the fluid level at all times while bleeding? I know it took me a couple of bleeds before I got all the air out of the clutch line, but not as much as you describe.

How about giving the brakes a quick bleed and then trying the clutch again? Failing that, my guess would be a bad slave if the brakes are working properly. (And it really is just a guess!)