'05 with a 5.3. Symptoms Temp guage reads at the 3/4 mark within 5 minutes of startup. When left to sit at idle for 5 minutes, temp guage went down to normal. Start to drive and it goes back up. Heater blows out cool air. When running, squeezed the radiator hose, felt like nothing was passing through. While it was hot and running, I watched the OEM electric fans for about 5 minutes, and they did not come on. No visible leaks. Will check coolant level when truck cools down. I'm going insane trying to pinpoint exactly what part of the system is screwed. Any thoughts?