Ok, I think I have a faulty radiator. I've narrowed it down to the radiator cap. When I got home from work today, I took a look while it was running. No bubbles...so I tapped the radiator cap, heard a "gurgle" then started to see little bubbles start to come up in the overflow tank about 1-2 bubbles every second. Only thing I can think of is that the radiator fill cap area isn't "flat" or flush...