I've had my truck over a year now . The heat has been sub par at best. Mostly only being hot on first two settings. If I turn on high it was cool air pretty much. So after some research on here I read about flushing the heater core. I did it today. A lot of brown dirty water ame out. I also reversed it until water was clear. For good measure I put a new heater valve on too since it was cheap. Now the heat is so hot it's almost unbearable, on all settings too. Even when sitting in park it's hotter than ever. Something it never was able to do. What a good simple trick. Now I have to overhaul then whole cooling system since my rad spring a leak.