My 2003 buick lesabre is overheating. I have a new radiator, new thermostat, 50/50 coolant. Its still running hot
Off the top of my head, you might have air trapped in the cooling system. Run it for a while with the heater on high and check the coolant level.
Check the color of the transmission fluid,
If it’s dark or black,
the transmission is running hot.
And if the transmission runs hot, it can cause the engine to overheat.
Tester
Are your radiator fans running when it is overheating, and is it overheating in heavy traffic, at idle,or over 50 mph?