New radiator probs

[74chev4x4]

Ordered a new aluminum rad from a rep seller on ebay with good feedback, radiator is great put it in today and hooked everything up and thats all fine.  Started the truck and my tranny lines at the radiator leak, it was just the one at first so I messed with it for a while and could not get it to stop so I figured I would bend up two new tranny lines.  I did this and to my suprise they came out well for my first time.  Hooked everything up and boom both lines leak like crazy.  Thought ok maybe I need to put some pipe thread tape on the threads, start it up leaks everywhere.  Is there something I am overlooking here guys?  I love working on my truck, but it seems that I just dump money into it and it sits in the driveway with the hood up 90% more then I get to drive the dumb thing.  75 chev 4x4 350ci turbo 400.  Thanks.

[Lt.Del]

sure it was the right thread size?

[74chev4x4]

yea 5/16" they threaded on with no problem.  I am always really careful with these types of lines not to cross thread them.  Seems like it is leaking from inside the nut where the line goes through not at the threads, but its both lines.  Never had a prob on the old radiator?

[Psycho71]

Just a thought here. The radiator I bought off of ebay had NPT threads into the radiator for the trans lines, and used a brass adapter fitting for the flare connection to the lines. Mine came with the adapters though, so it was no big deal. Is this the way yours is? Or is it possible you are missing the adapters?

Or....Did you cut and re-flare the end that connects to the radiator? These are double flared connections, and are hard to get a proper seal if a single flare is used.