Thanks for the link and your are the first one who is suggesting a 79C Thermostat.
Do you know where I can get this thermostat?


I was already suspecting the gauge having an issue. And I bought an infrared thermostat in order to check if the temperature shown in the dash can be verified with the measurement.

Pierre is stating that the temperature should not reach the 100C mark.
And I agree!
All my other Mercedes don't do this and stay around the thermostat temperature or slightly higher (probably up to 5 C higher). I'd very rarely see
90C.

He is also mentioning an air lock at the sensor meaning the sensor cannot sense the water temperature correctly because the probe is in air and not the water... However I don't know why the 'sensed' temperature then might be higher.... because the enclosed air cannot be hotter than the water unless there was a sudden water temperature drop while the air might be still hot...However a sudden temperature drop is probably not realistic.

As the radiator, water pump and visco fan clutch are all new ... the 79C thermostat might be a good option.

Martin