I highly suspect a crack where the upper hose fitting is attached to the main radiator, on the bottom where you can't see it. Folks pull/pry/etc on that upper hose to get it off, and they crack and seep.

Were it at the filler neck, I'm sure you'd see evidence.

Weld, absolutely not.

Solder, yes. But one must be very, very careful not to melt other nearby solder at the vanes. You melt that, and you might as well get a new radiator. (we are talking propane torch and plumber type solder here, so not totally easy to localize the heat)

That said, I'm no expert, and I've successfully fixed many. I'm sure you're welder friends would know what to do.



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-Matt I ♥ my ♂