Tiny, I made a rope of twisted teflon tape and wrapped it around the tube, then put some teflon tape on the threads and tightened it down. That helped, but didn't stop the leak entirely. The leak DID stop overnight, but it's still damp there, and once the engine is started and/or I hit a bump (assuming I ever get the truck on the road), I think it would leak again.
No, I didn't coat either the male or the female nipple with anything. The leak appears to be at the threads between the two, and some kind of locktite solution might be what I need to do. I would have thought, though, that the end of the male fitting would seat against the inside of the female fitting to provide the seal, thus thread dope wasn't important.
If it can be sealed that way, good. I thought soldering the joint at the end of the threads might do it better, and more permanently, but I don't have experience with soldering brass, and it's not in an easy spot to get to. I have no intention of taking the tube out again, and if I did, the engine would be out of the truck, and I could back out the female fitting until it snaps off, so soldering wouldn't hamper anything in the way of engine repairs.
Atomarc, I've been thinking like you - something is probably wrong with the fitting. I got the assembly from NAPA, and who knows where they get their stuff. I'm also dealing with NAPA to solve my other big leak, the water pump. I hope I have better luck with that.
