Truck reading hot
 

I'm new to this forum and really looking for help on here. I have this 2000 3.0L 2wd montero ls truck that I'm working on and it's reading hot but not running hot. It started when they were out of town when their radiator busted. On the way back they had to stop every 10 mins to replace water in it but they eventually made it home. Well, I've since change the radiator and thermostat and it's still reading hot. I think it's the tempature sensor but then again I'm not sure. But sometimes it's hard to start which I also think they cracked the head but I want to be sure that's it or not. There's no water in the oil, which in some cases you can't even tell there, with the caramel looking oil. I would like to purge the system of air but don't know where the blled hole is. Is it that allen bolt on top connected to the top radiator hose? Another thing is when I tried topping it off and doing the procedure of turning the heater on to circulate the coolant, the heater doesn't even get hot either. It's like cool warm air. The top heater hose is very hot but the bottom is warm. Well anyway...I could really use some help. Thank you guys in advance.

So no thoughts on what it could probably be?