you are not alone, I have a 1994 Chevy Lumina euro with the 3.1 liter that does the same thing.......i have found after setting while car is running the temp will go up almost to the red and then will start dropping back down once it gets up there..... and i also was sitting at a drive thru window where it did this, my windows were open and i heard the cooling fans come on......they came on once i put the car in park, but that's all i know.
Have you checked the coolant levels or the cooling fan?
Your reservoir may be low. This will trigger the coolant light. It is often a malfunctioning sensor and nothing is actually wrong with the cooling system or coolant. It can be easily replaced. Alternatively you can leave it, but monitor your engine temperature and coolant level.
Have you checked for leaks? also the cooling fan may not be working.
I would have the cooling system flushed and coolant replaced. DEF is very caustic.
I own a 2000 with cooling fan probs check your coolant temp sensor,changed mine and cooling fans work perfect bhasche@yahoo.com
this is normal,because the coolant temp sensor is supposed to be in direct contact with the cooling fluid in order to read its temperature
Air can get into the cooling system when the coolant is replaced as either part of a maintenance schedule or when the system must be drained for a repair. When the coolant is replaced the coolant system must be "burped" to get any air out of the coolant lines. There are various ways to do this dependant upon the type of vehicle. A repair manual for your vehicle will describe the proper technique.
OK, you know the fans are good because the work when the A/C is on. So the problem is elsewhere. As you know, there is a temperature sensor that signals the fans to come on when the cooling system gets warm. You replace it, but is the wiring OK. Check all connections. The fan control module/relay may be faulty, have you checked it? THE PROBLEM WAS I NEEDED A DEALER COOLANT TEMP SENSORS
Where is the temperature cooling sensor located
Keep the engine coolant or antifreeze from rising above its operational temperature.
Higher pressure raises the boiling temperature of the coolant.
Sounds like your cooling fan relay is shot. Ron J.