My 2004 kia is running hot

I have a 2004 kia Optima just put new radiator in about 6 months ago yesterday car start running hot check the thermostat it is good and also coolant bubble up and back up what's wrong

I had a 2005 Sonata which is the same car as yours and was doing the same thing. It turned out that one of the ground connections was weak and the cooling fan was not getting enough power to run at full speed to cool down the engine. It took a while to narrow it down. I would check the ground connections for corrosion especially the one from engine block to frame. Also check out this article, https://www.youcanic.com/article/common- causes-car-overheating it lists a number of possible issues.