On my way to work this morning i did not have heat in my vehicle. Truck ran fine. On my way home I still do not have heat and I noticed a wooshing noise coming from the engine bay. The engine temperature was running slightly above 200 would creep up to about I would say 230 then back down to just above 200. Still no heat. This was all on the highway. 70 plus mile an hour speeds. Once I hit the surface streets the thermostat quickly rose the point where I felt the need to shut the engine off and let it cool. What's going on with my truck? 2004 Ram 2500 diesel automatic transmission.