Hey guys, total audi noob here. I am a bmw guy (don't kill me!)
Just bought an a4, it is a 2000 Audi A4 1.8TQM

The clutch has ZERO resistance, I can sit with the car running and shift into gears but nothing happens. I get the impression that the clutch slave cylinder went bad.

He said he was driving and pressed the pedal in, and it stayed on the floor and did not return. From then on it was like the clutch was always pressed in, regardless of where the pedal was.

Based on my limited mechanical knowledge I've narrowed it down to either the slave cyl or the linkage for the pedal.... Am I wrong guys?

 

If the pedal has zero resistance when pushed down and does not return then the slave is most likely bad or the line has a leak. You should see fluid near the slave or maybe dripping out of the holes on the bottom of the bell housing.

Problem could also be a bad master cylinder. Usually when the pedal stays at the floor it is a bad master cylinder or the slave has popped.

If he starts the car with it in gear does the car move forward?