Hi guys. I posted few times about my truck, seems I got oil cooler going bad. The temps about 20 degrees off. I plan to get fix in next month. Anyways my heat started acting crazy While back and I really just hadn't worried much cuz it is summer. Anyway like you get in in morn no heat, drive for while it starts working, then seems like it stops working again then starts back. Usually after that it works fine but again it's summer and only reason I use is for dew in mornings. So this morn I pay little more attention and it seems soon as coolant and oil temps hit around 190 the heat starts working, then if you stop let idle it quits again until you take off. I'm starting to wonder if it could be thermostat problem? I mean could it be stuck open or not opening ( closing ) soon enough? Thks for any help guys, I don't know alot about the thermostat on these diesels..