W213 E200 facelift - Low coolant temp, does tha show error ?

[Dewi 2]

After a cold start the heater very soon produces warm air, so I presume that heat must come from hot coolant.
There are no error messages on the dashboard.

However after driving a couple of miles, the centre screen graphic on MBUX (Info / Vehicle / Engine) shows the oil temperature heading up close to normal, but the white line for coolant temperature has even not begun to move.
Strange because coolant usually heats more quickly than oil.
If the sender unit was faulty, would an error message be displayed?
Need to drive more than ten miles for the white line to even be approaching minimum.
My guess is that the actual coolant temperature is normal, but that the display is wrong.

Any comments please?

[trevalvole]

Replies to posts mentioning coolant temperature usually say that the value displayed to the driver in modern cars cannot be relied upon and is some kind of ECU calculated value, rather than raw data from a sensor.

[Dewi 2]

Thank you trevalvole.

As mentioned, I did suspect the graphic display of the water temperature was wildly inaccurate.

Do you know whether a warning message would be displayed, if coolant temperature is too low?
If it is, I do not need to be concerned.

If they can state various other information accurately, you would think correct coolant temperature should not be beyond their capabilities. As you have commented, an ECU seems to be no match for the old days of sensor, wire and gauge.

It is a pity that we cannot send an email to someone directly involved. Dealers are too far removed with this kind of question.

[trevalvole]

Dewi 2 said:

Do you know whether a warning message would be displayed, if coolant temperature is too low?

Sorry, I don't know whether that model has a warning message for low coolant temperature. I have had cars that didn't have a coolant temperature gauge that used to display a blue water temperature symbol until it was up to temperature.

[gregpot2000]

I don't think your car is malfunctioning, my W213 is exactly the same. Mine is an E220 diesel though and these have an additional electric heater to help out before the coolant reaches temperature. It wouldn't surprise me though if the same is now fitted to petrols.

I get hot air exactly 2mins from setting off, and that is with the start of my drive being all down a steep hill so it's definitely not from warmed coolant. Coolant temp can take around 20mins to reach full in winter