My Jeep just started overheating tonight. The odd thing (to me at least) is that if I keep the RPMs high the engine stays cool. So if I'm going down hill at 70MPH in neutral (idling) I can watch the temp gauge go up. As soon as I put it in gear and give it gas it cools back down. When traveling at slower speeds I have to keep it a gear or two lower to keep the RPMs up and it will also stay cool.