am a new owner of a 2011 Ram 3500 6.7 Cummings. I am having an overheating problem. I understand I bought a used truck, but here is some background on what I have already tried. New waterpump, thermostat, thermostat housing, headgasket, machined /rebuilt head o-ringed, head studs, new radiator , new radiator cap, confirmed clutch fan working. Heat goes away, tried to bleed air out of the system refill and the heat comes back. Then it will be good for a while, 1 hr or so on short trips. Then stop, cool down maybe overnight, then check the system add coolant , then I have to start the whole process over. I just finally the head work today, started, ran at high idle and started to get hot no heat, bleed the pressure off and topped off the coolant. Heat returns and stays, temp stays good. Shut it down, check the coolant level after bleeding pressure off, top off coolant to a tune of 1.5 goals. Start the truck back up and it starts all over again. No heat, after about 20 mins of running, runs hot again. The reservoir is full and doesn't appear to draw coolant back in when needed. Help, Ideas, I'm at my wits end!!!! It does have the egr deleted.