Truck runs fine and warms up normally, then once it's warm it gets really hot fast. Blew the upper radiator hose off on the highway. Tested Oil - no coolant. Tested coolant, no gasses. So maybe the head gaskets are fine. Replaced the water pump and the thermostat. No change in behavior. Pulled the radiator to have it flushed and the nipple for the coolant tank hose fell off! Replaced radiator. Replaced both radiator hoses and when replacing the one connected to the cabin heater, it's nipple just disintegrated! So, trying to figure out how to force flush the system BACKWARDS before I connect the new radiator in case it's got bits of crap in it from disintegrating plastic parts. So, I was looking at the thermostat housing (replaced 5 years ago because it cracked) and trying to figure out how it actually works. Anyone have a diagram? I've searched and have not found what I'm looking for - specially the housing and how it works. Any suggestions on flushing the system? Any suggestions on what the problem might be? Thank you!