what would cause me to be losing coolant over time? I don't visually see any leaks, and my heater doesnt blow hot air. Besides that, I would have to fill up a small amount of coolant after a drive, or if I boost, then I can see my oil pressure start to drop a little more (due to coolant lost), my temperature would start to move up, and my overflow would be filled up completely. Once again, visually I don't see any leaks, not from the waterneck area, lower radiator hose, nor around the back by the firewall. Help?