Have a 03 Kia Optima with a 2.4L engine with 120K. The car recently started overheating occasionally mainly while stopped in traffic. Both fans are running and as soon as I get rolling, the temp gage goes down. I’ve noticed that it only happens while the trans is in gear. if I put it in neutral, the temp will drop to normal.
I replaced the thermostat and radiator cap thinking these may have been contributors. I also replaced the temp sensor because it controls both the gage & the cooling fan. Both fans operate with the a/c on but the single fan will not come on with a/c off. I tried another pcm from the salvage yard but still get the same operation. My next thought is to install a separate trans cooler to the radiator which is only 2 to 3 years old.
What could be causing this overheating & how can I fix it? When it does over heat, I usually turn the heater on full blast to help bring the temp down. Car is in great shape and would like to get it back to normal