engine won't get to normal temp
 

1990 560sel changed the thermostat but the car won't get to 80c it is running at 60c. does anybody know why?

Maybe it is getting to 80, but the indicator is bad? Is there a way to check the temperature with a thermometer of infra-red device?

I have no idea how to diagnose / repair such a problem, but I would start at the temperature sensor. I am guessing it has a certain resistance at a certain temperature. Or could be a corroded wire connector at the sensor?

temp
 

i concur ,the sending unit for the gauge which should be on the thermo housing must be bad.you can find it by warming up car and pull the conn and gauge should drop to zero.

I'd suspect a faulty sender...they do fail with age.

Do as mentioned above w/ the non-contact thermometer.

The temp sender isn't very expensive, you might just reaplce it as a matter of course.

Jonathan