Temperature fluctuation

Hi,

It is unlikely that this is the thermostat because usually these get stuck open or closed. They don't normally cause drastic fluctuations like this.

https://www.2carpros.com/articles/symptoms-of-an-overheating-engine

First thing to check is the coolant level. If the level is low, then this would explain the swing.

If it is not low then it could be the sensor. The easiest way to test this is when you see the gauge high, to use an infrared temperature gauge and see what the temperature is around the engine. If your temperature gauge is showing high or around 250-280 degrees but the engine is only low 200's or below, then you know the temperature sensor is not accurate. It may not be easy just because it is hard to catch it while it is acting up. However, I would hate for you to just replace the sensor as a guess.

Next thing, is to check if there are any codes. If you don't have a code reader then any parts store can pull them for you.

It could be thermostat if the swing has a pattern to it. Meaning it is basically doing the same thing each time. When they stick, they either stick open or closed completely, or they hang up until the coolant reaches about the same temperature and then it opens. This creates the predictability.

I attached the location of the temperature sensor if you find it needs to be replaced.

Please let me know what you find and we can go from there. Thanks