leaking clutch slave line/connection 2.7T 6spd

[vtraudt]

Replace the clutch slave (plugged, not bleeding) with a metal Wagner (SC141816) I was able to get quickly locally.
All fine, no leaks. But 200 miles or so later, lost clutch completely. Fluid leaking out big time from the hard line connection into the slave.
First thought the retaining clip had popped out, but line still in place.

Line had quite some play.

Pulled line, reconnected/reseated: leaking

Pulled line the 15mm socket hex shaped connector 'nut'.
http://www.rockauto.com/getimage/get...ac%2Fs1705.jpg

In the remaining screw-in nipple coming out of the slave body is an O ring. Looked 'frazzled'.
Tried to get matching O ring from local store. Leaking (tried two close sizes).

Finally decided to give it one last shot (car stranded at friends place 2 hours away) and silicone sealant on the hard line including the plastic 'cone' (behind which the clip goes to hold line in place). No leak.

Started bleeding the slave.
Started to build clutch pressure.

Then the hard line popped out (retainer did not hold).

a) Called the place I got the Wagner slave from: they can't get another one. Does anybody know what O ring I need to get?
b) The retaining clip looks very 'loose'. Since it was tight for 200 miles, can it be the looseness and resulting movement could have worn the O Ring (and potentially 'rounded' the plastic 'cone' on the hard line that provides the seat/hold for the retaining clip)?
c) Is it possible to replace the clutch slave hard line with the engine in place?
d) Are there differences between clutch slave lines and clutch slave between S4, A6, Allroad 6 spd transmissions?
e) is it possible to get rid of the 'cone and clip' connection by cutting the hard line, putting a brake line 'splice' and make an adapter on the slave?
http://image.gmhightechperformance.c...brake_line.jpg

[vtraudt]

This is the connection. Note how little of the retaining spring 'penetrates' behind the hard line plastic 'cone':

[khalimadeath]

I got the USP stainless steel line for mine it seems to fit quite well.

http://www.uspmotorsports.com/USPAud...lutchline.html

[MetalMan]

Bumping this up. My S4 came with a metal clutch slave cylinder, unknown brand, installed by a PO.
I had noticed what seemed to be brake or power steering fluid leaking but didn't think much of it, especially since the car often wasn't parked in my garage.
On the day I pulled the S4 into my garage, it didn't actually make it (lost clutch operation), and had to be pushed into the garage. BRAKE light was flashing and beeping, I learned because the fluid was low.

Found brake fluid leaking from the connection between line and slave, same as OP.
Took the slave off, removed the inlet connection fitting, and found out I could disassemble that fitting. Here's the seal in that fitting:

https://photos.app.goo.gl/SbiWnJ4MDvRyQkDe8
https://photos.app.goo.gl/1VFb3XBADxPkEwBu7
It appears to have "unrolled" or something; in any case that definitely caused my fluid leak.

https://photos.app.goo.gl/GDiz1URAAiKozPDr5

Took some measurements, and bought 2 sizes of O-rings to try as a replacement. This was the best fitting O-ring I found: size 009, material EPDM which is supposed to have excellent resistance to brake fluid.
https://photos.app.goo.gl/TGi6BwuhDY4114yz7

Plopped on a little thread sealant for good measure (not needed IMO based on the way the O-ring seals) and reassembled the fitting, then reinstalled back onto the slave cylinder:
https://photos.app.goo.gl/GDiz1URAAiKozPDr5

Early test fitting with this O-ring felt like it's a good size to suit the clutch line and fitting, with a bit of squeeze/friction.
For reference I found the fitting's bore is 8.8mm, and the clutch line shaft is 6.0mm. I used an imperial size O-ring, with "actual" dimensions of 0.208" (5.25mm) I.D. and 0.348" (8.84mm) O.D.

UPDATE: this didn't stop the leaking. I ended up replacing this garbage slave cylinder and the stock line to get rid of that stupid interface entirely:
https://www.audizine.com/forum/showt...9#post13127139