Audi A4 B8 clutch question

[MI55INU]

Looking if anyone could advise what is going on with my car. It’s a 2008 Audi a4 b8 2.0tdi 6 speed manual. The clutch pedal went to the floor & wouldn’t return (no resistance). Suspected the issue to be the slave cylinder so this was replaced (Borg & Beck). System was bled & the resistance in the pedal returned however, the vehicle would no longer start as it wasn’t detecting that the clutch was de-pressed. By pushing the pedal down really hard, we managed to get the vehicle to start. The bite point on the clutch was very low but it did go into gear ok. Unfortunately, after 5 minutes of driving the same thing happened. The clutch went to the floor with no resistance. There’s no evidence of a fluid leak & with the cylinder being external I think a leak would be visible. I’m now back at square 1 & I’m not sure what is causing the issue…

Any advice / suggestions or similar stories would be appreciated
Thank you

[Wheatsheaf]

I'd suspect a failed master cylinder in that it's letting fluid past the piston seals. After bleeding etc it just about managed a few pumps and could disengage the clutch a couple of times (and allowed engine to start) but it's basically knackered and can no longer push fluid to the slave.

It's possible the slave was OK all along!

[MI55INU]

Cheers
Will give it a go!