For the entirety of my ownership of my '91 240, there has been a fairly inconsistent issue, but weird happening where the car gets up to temperature, then the temp gauge skyrockets up past the red, lingers there for a bit, then falls to the "normal" marker. It may do it a few times while driving. Now, it has become an every day, every drive occurance.

I have recently bequeathed the car down to my little brother who has grown nervous as the car approaches 350k of being able to detect when the car actually has issues or may really be overheating.

We've replaced all of the usual suspects, including the thermostat multiple times. Clearly it (probably is) an electrical issue (which I know can be like trying to find a needle in a haystack) but figured i'd reach out and see if anyone else had experienced the issue and had any luck with a fix.

Thanks in advance