Ic3Cub3

Hello Guys,

I need some guidance as i`m stuck.
I own a e300 petrol 2017 - Temperature gauge started fluctuating while driving - temperature was going down.
Change thermostat as it was stuck open - it improved but not by a lot.
Changed Coolant sensor - nothing changed.

Temperatures go down to 75*C while at a red light and while driving goes up to 83*C-85*C but drops when slowing down or stopping to 77*C-78*C.

It reaches 90*C but not easily.

Don't know what else to check...

1guitar

It sounds like the sensor might be shorting out due to some other malfunction. I know you have the same engine as I do and while the E300 is a pretty reliable car it does have its quirks. In any case I think the only way you’ll find the problem is to bring it to the dealer and let them hook it up to their computer that can test for such faults. While I’m sure it’s annoying I doubt the engine is in any immediate danger of having a “meltdown”. Good luck.

Ic3Cub3

I think the Instrument Cluster needs a rewrite - yesterday i powered up the car while it was still hot - around 50*c - I rewed the engine and immediately temps dropped on the dash and on the diag even if i was standing still..

I went to the dealer as they changed on warranty the thermostat - will come back with updates/fix

Ic3Cub3

Update*
Instrument cluster updated - no change.

Ic3Cub3

So issue has been solved.
Except the mechanical issue of the thermostat - issue was only solved after rewriting/updating car`s computers, they reported that all of them were updated.
ECM,ECU,Instrument cluster etc - that sorted the bug/issue/error.

Diesel Benz

Do you know if the engine temperature was really fluctuating as you described before the fix or if the cluster (and OBD port) just reported funny figures?

Ic3Cub3

Issue should have been fixed after the thermostat has been replaced.
The rest were just bad reading from ecu or other computer.

rJzzz

I have the same issue with you, I bought my own thermostat and installed but not really worked. I wonder how much the dealer charge you for the software upgrade?
best

Ic3Cub3

Hello rJzzz

The dealership did not charge me anything for the software update as the car was still in warranty.
Unfortunately they were too stupid to know which is the faulty unit that needed software update so they updated the entire car to fix it.

I would recommend to ask first.
Tell them about the issue and that someone had a software issue after faulty thermostat and that it was solved only with software update.

Ask them for a quote first ,I am sorry i cannot help your further.

Best of luck !

rJzzz

Well, I’m appreciate your help. I called today and they said they need check the vehicle first and it will take $340 plus tax. I only have limited warranty on this car and I’ll update it here later.