There is a bleeder valve on top of the thermostat housing. Start engine and get it to operating temperature. Crack the valve open and you will here and see air come out. Keep doing this until you get just coolant coming out. You may have to do that several times until you get the air out. Make sure you keep topping it off during this process. I did the same thing, replaced water pump thermostat hoses, cool can and cap. Everything you could replace. And it turned out to be air lock in the system. It's a lengthy process so don't give up early or it will run hot. ( Note) do it at operation temperature. If you do it hot, you will get steam and it will not work. The more you do it the better off you will be. It took me about 3 hours, between letting it cool off and waiting. It's. Easy but a pain and well worth it. The air will stop the coolant from circulation like it should. Hopefully that is your problem. It happens more than you think. My 3800 has been running the perfect temperature ever since. Good luck and stay with it till completely done.