Another place to find unwanted air that no one ever mentions is the top heater core pipe. Even with no issues, your bound to have air trapped in that pipe if you had the system opened up like I did as a replaced radiator. The fix is fit a funnel to a straw, pull the top hose 95 percent off the heater core but leave a slight opening at the top edge of the hose, put the straw in there and slowly fill it with coolant until it over flows and at that moment push the hose on and pull the straw out of the way. My temp gauge stays slightly below half no matter how the car is run.
