Engine overheating?

If its overly retarded-are the cooling fans coming On? Feel across the radiator should be evenly warm no cold spot if so its clogged up.

Try bleeding the air out by doing below

Always bleed air from cooling system after replacing coolant. Set heater for maximum heat. Remove radiator cap. Loosen drain plug and remove drain bolt (if equipped) from engine block. Drain coolant reservoir. Fill coolant reservoir to MAX mark with 50/50 water-coolant mixture. Loosen bleed bolt and fill radiator up to base of filler neck. Close bleed bolt when coolant flows out without bubbles. Tighten bleed bolt. With radiator cap removed, start and operate engine to normal operating temperature. Add coolant if necessary and check for leaks.

Don't work we'll work on a possible leakage thru H/Gasket/Head/Block.

If you're not losing coolant thru leakage then its being burn internally-any white smoke after engine is warmed-up or water dripping from tail pipe.

If you have a 3.8 engine, this could be a sign of a blown head gasket. If you have the 3.0 engine, it may be a plugged radiator or an inoperative cooling fan.

If it is a 3.0, is is not likely a head gasket. Start out by verifying that the cooling fan is operating. Once you have checked that, you can check the radiator by feeling it while the engine is running (keep hands and fingers away from the fan - it BITES!). Feel the tubes near the edge of the radiator while the engine is warm and idling. The tubes should feel consistently warm all the way from the top to the bottom. If you have cool spots, then the radiator is restricted. I would suggest that you just replace it if this is the case. A brand new one only costs about $150 from radiator shops, and can save you a lot of aggravation.

How hot does it get in degrees F? Your thermostat opening says, 197 degrees F. A fully warmed engine is over 200 degrees F. Is the overflow bottle filling up in a hurry or boiling? Any trouble codes relating to coolant temp sensor? Sometimes for testing, I leave the thermostat out, hook everything up, then check coolant flow into radiator, cold engine. The flow in instant, you do not have to wait for anything to warm up. Depending on the radiator, you can see or feel the flow.
Some makes and models, if you unplug the coolant temp sensor, the fan will run all the time.

Suspect and check for head gasket failure