Ok, I have a 1998 Chevy Lumina.
It was overheating, so my dad replaced the thermostat.
I took it on the interstate and it did great!
Then I got home & was letting it idle…
That’s when It overheated, again.
Anybody have any ideas on what this could be?
I google’d and seen a lot about radiator fans…
It sounds like your radiator cooling fan is not running when the engine is idling hot. Try turning on the AC when the engine is warmed up and see if the fan comes on. If it does it probably your radiator cooling fan relay. If the fan does not come on with the AC then it may be a wiring issue or the fan may be defective. The Lumina does not need a cooling fan on the interstate since there is a lot of air going through the radiator. At idle, it’s another story.