So when it is overheating in traffic, the radiator fan is coming on full force? And even with the fan on, it still overheats then?
I guess if I had this problem, I’d suspect an air leak somewhere, the radiator or resevoir cap, hose, gasket, etc. It’s possible for a mechanic to pressure test the cooling system to see if it is holding pressure correctly, that might be a good idea. It could be the water pump is just not pumping enough water, or the radiator is clogged up. A radiator shop could probably test the radiator for you, and declog it if necessary. And there’s a chance the head gasket is starting to fail. A mechanic can do a chemical test for exhaust gas in the coolant to rule this out or in. If everything turns out negative, then replacing the water pump might be the next thing to try. Make sure the water pump belt is in good shape and tensioned properly of course first. A slipping belt could cause this symptom.