OK- - - - -you've got a gravity flow leak somewhere, and the water jacket line is a definite possibility, but that should have shown up on a pressure test of the cooling system. Changing that line is pretty tricky. You need to cut the old line off at both ends and thread a piece of stiff wire through the remains of it to act as a guide for the replacement line, plus about half a dozen other tricks to assure a good replacement that doesn't leak when you're done. If you had antifreeze in the radiator, now the whole oil system is contaminated, and needs to be flushed thoroughly.
Jerry
