Martin,
I feel the same as you...heat or not, it would leak under pressure. Looking through the forum at other threads on this same subject you see numerous references to the fact that it only leaked when hot, or it only leaked when the supply tubes were tweaked, or it only leaked in the winter etc. If the shop tanked the core, put pressure to it and got no bubbles, then, assuming the radiator guy wasn't blind, it wasn't leaking
This means that the heat affects it more than we think, or that the drip is coming from a faulty valve or a leaking hose...I would guess that the valve isn't hooked up and it's a hose. I bet a root beer on this same subject several weeks ago, and guess what...I'm down one can of soda! I hope we hear the outcome of this saga.
Stuart.
