Hello anyone. new guy here. Parents 1998 v70 base loses coolant and over heats. replaced ECT, thermostat, and coolant level sensor and the car still runs hot. The temp gauge goes to the middle, but my OBD shows a rise in temp. If I unplug my ECT the gauge stays in the middle. the only time my temp gauge spiked, was when the OBD showed 120 degrees C. Where is the temp gauge getting its info?

 

I think from the ECT.

 

In some cars, and maybe V70, the gauge is not real, but more of a faux gauge that is really an idiot light. If so, it would sit in the middle of the display while you are in the acceptable range. This would explain why you saw it spike once, when you were outside its range of OK temp. Your OBD will be giving you the actual temp.