Do the connectors have flare fittings, or "O" ring seals? Normally, there's a pipe thread in the radiator tank, with an adapter fitting going from female pipe threads to inverted flare fittings. If you're trying to screw the flare fitting into the pipe threads, you've messed up big time!

Some of the newer teans cooler lines use a special fitting with an O ring seal, and those fittings will allow some movement without leaking. Ford is the only manufacturer I'm aware of that's using that kind of cooler line fitting, however.
Jerry

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