I would also check your heater when the engine begins to overheat. With the heater temp set as high as it goes, and the heater fan on high, do you get a lot of heat out of the heater, or none at all?No, I haven't! I can't believe I didn't think of this. I will check that. and if that isn't the issue, is there anything else I could check?
No heat at all means either no coolant circulation or a blocked heater core.
Plenty of heat means good coolant circulation (at least through the engine) and the heater core is not plugged (meaning a stuck closed thermostat or the radiator cooling fans are not operating).
If the heater works well, but the coolant temp starts to elevate above normal on the radiator, I would check (by hand or infrared thermometer) the temp. of both the upper & lower radiator hoses. Are both hot? If so, good coolant flow. If not, for some reason, restricted coolant flow through the radiator.
If both hoses are hot and the temperature gauge is going up above the normal operating temperature, the radiator fans should be on. Are they? If not, your radiator coolant temperature switch may be inoperative. I believe if you disconnect the wiring harness at the switch, the fans should run. Do they? If so, the radiator temperature switch is bad. If the fans do not operate, you should check your fuses. You may have a bad fan or both fans may be bad, which may or may not blow your fuses.