autto.net

It's running hot or you put too much coolant in the car.

more than likely the car is overheating. make sure that the radiator fans are coming on even and specially with the AC on.

? year and model, how did it started doing that. was it after a radiator flush? did the car overheated and the idiots light came on? btw that light is called idiots light no punn intended.
even if the car has a water leak and you filled the overflow with other than DEX COOL if the car calls for that coolant the car will overheat regardless if the overflow reservoir is full or full of other than DEX COOL anty freeze.

also if you have a newer model you need to look under the hood or around the engine bay, or even written on top of the radiator overflow cap, there should be a sticker that says DEX COOL. if you used an ORANGE anty freeze / coolant and its not DEX COOL IT WILL overheat. trust me it will.

if you dont know how it started then its time to bring the car to a trust worthy mechanic.

gl

"Details" Bad Radiator Cap

change the radiator cap.