Lurker and not a poster, but have gleaned a ton of great information here! Thanks. Now my problem, did a search of overheat issues and couldn't really find an answer to my problem. Truck sat for a week, and was not overheating when it was parked. Now it overheats within a few a few miles, cools back down at idle. The heat in the cab is great and doesn't fluctuate at all. If it was low coolant would I still have heat ? the weather hear has been in the single digits, don't know if that is a factor or not. Any help or thoughts ?