As a diesel mechanic in Nebraska for a few years, I've found what and seems to be a well known problem in colder climates. That is as the cold weather sets in the connections around and normal worm clamps and rubber hose would start to leak as everything shrunk with the weather. Sounds a little odd but it does happen. I've seen it "pouring" out to a slight trickle. A tightening of the clamps fixes it for the whole cold season and longer. New truck and old, it happened. Glad to hear that you got it fixed and I agree w/ Klaus in that it was a microscopic leak too, but a bad smell is a bad smell.