brake lines

[SouthwestSpider]

I just installed a new master cylinder from Auto Ricambi. My critter is an FI 1980 Spider. The old brake lines sealed well at the master cylinder, but I have the rear line giving me a leak at the center of the nut when I tighten it down to the output of the master cylinder.
My question is how can I establish a seal with all my lines at the master cylinder. Does teflon tape work? Pipe dope? or ??? I really, really need to get this line sealed and tight. I'm surprised it didn't snug down like it did on the old master cylinder.
All suggestions welcome.

[vandor]

Teflon tape or similar won't work, as these fittings do not seal at the threads. They seal by pushing the bubble end of the line against the machined surface of the MC. I'd check the pipe for cracks at the end, or foreign object, dirt, etc in the hole. Sounds like it is just not seating all the way for some reason. The only time I had this happen was when I cross-threaded the fitting into the MC...

[4uall]

here is a good video on how a taper makes its seal

http://www.youtube.com/watch?v=pALz0z8bpfY

[SouthwestSpider]

thanks - I'll see what can be done today.