C180 1.6 M274 Coupe - Unstable Temperature

[FelipeGrandin]

Hello, how are you?
My name is Felipe, I'm Brazilian and I own a C180 1.6 2013/14 with the M274 engine.

My car has an unstable temperature.
In small circuits the temperature hangs in 90 degrees celsius
But if I'm walking on a road at 120km/h the temperature drops to 65-70 depending.


I saw that some users changed the thermostat and resulted in correcting the error.
Is it just the solution to this error?

Thank you

 

[grober]

The symptoms you describe might come from a faulty thermostat or they might just be the result of a faulty temperature readout. The cooling system on the M274 is complex--- see this link below. I suggest getting the car checked on a Mercedes STAR diagnostic system before replacing any item.
https://www.motor-talk.de/forum/aktion/Attachment.html?attachmentId=758372

 

[FelipeGrandin]

The symptoms you describe might come from a faulty thermostat or they might just be the result of a faulty temperature readout. The cooling system on the M274 is complex--- see this link below. I suggest getting the car checked on a Mercedes STAR diagnostic system before replacing any item.
https://www.motor-talk.de/forum/aktion/Attachment.html?attachmentId=758372

Grober, thanks for the reply

My car has already passed the Star Diagnostics, the engine module has been updated and everything is ok.

I see no other solution than to change the thermostat.
Is it also necessary to change the temperature sensor?

Thank you

 

[grober]

Your car also has variable radiator shutters to restrict airflow - perhaps these are broken/stuck open so that at higher speed your engine is overcooled? see page 18 of the link. I am not sure where your temperature readout on the dash is generated from? It may be from the same coolant temperature sensor the Engine ECU uses or a separate one-don't know-- however a tempertaure sensor is going to cost considerably less than a thermostat so I would be inclined to change that first.

 

[FelipeGrandin]

Good Morning
The problem was solved!
I changed the thermostat and the temperature is now stable.
I also felt that the car raises the temperature easier and there is no variation when it reaches around 90 degrees

thank you so much!!