Hi,

i have eclass 220 2011. Its been very good with him until recently. The issue is that when i am driving in motorway going after 40 min drive in uphill drive temperature goes to 100 and twice reached nearly 120. No temperature red light. But as soon car decelerate and going downhill temperature goes back to 90. In domestic drive for 30-40miles no issue. I have checked with dealer he said bo issue and cleaned the thermostat. But now he is saying since no error the only thing he can do is change the thermostat housing. Collant level is fine. Can anybody advise?

 

We don’t see too many diesel equipped cars here, so there may be heat related issues with this motor that I am not aware of. In any event, neither my W211 or W212 cars have ever had a gauge reading above 95c no matter what the driving conditions. I have had failed thermostats before, though and you will generally get a CEL when it fails. Mercedes thermostats fail in the open position to prevent engine damage and you will see the gauge post lower coolant temps not higher. You read the code, see the lower temps and change out the thermostat. I’m not sure what you may have going on, but doubt it is the thermostat. Perhaps your coolant is not up to task any longer.

 

thanks. I have appointment with dealer this week for thermostat change. For coolant I had 6 month before my water pump changed it was leaking and dealer put new coolant so I dont think so its coolant related issue unless they put cheap coolant

 

Interesting that you have also had to replace the water pump. What was your indicator that you had a defective water pump? Was it leaking?

 

yes it was leaking. My car have done 110k

 

Ok, please come back and let us know how you get along after some time with the new thermostat. It will help others to diagnose similar situations.

 

will do. Thanks

 

I had a thermostat fail and it failed not to open enough. When I changed it, it was completely closed.

For me it sounds like the OP has an issue with the thermostat not opening enough so it does not allow enough coolant flow for cooling under heavy engine load.

My bet it the thermostat has gone bad.

 

thanks for comment. I have appointment with my dealer tomorrow to change thermostat housing. He already bought it. I hope that is all it need. Will update you guys here.

 

Hi. Just to give you update that I had thermostat housing changed couple of weeks befor but didnt go for a long drive until this weekend. I have driven nearly 200m miles and temp kept steady between 80-90 C. In some instances I can see that it came down to 80 but then went up between 80-90. i am happy now as its been troubling me for a long time. Thanks.

 

Improper concentration of the coolant-water ratio and poor mixing water quality, can damage your water pump.
In my case , a local assembled car, MB Indonesia assembled that is, I got at least the poor water quality issue as I can't verify 50/50 coolant concentration part, but is is a highly suspect too.
The probem is , the damage need years to show itself and in my case 4 years and at 17,000KM . For my case it is the duration not the mileage.
Do pay attention on the water quality workshop uses to mix the 50/50 with coolant concentrate.
https://mbworld.org/forums/e-class-w...i-am-sure.html

Glad to hear you solved the temperature issue and getting back to the forum to close the case.
Did you get to see if your thermostat issue is due to mechanical wear and tear or some sort of mineral deposit ?
Your post kinda triggered me to wonder about potential mineral deposit inside my "sealed" thermostat housing, which I can't inspect internally on this 3 liter, it is kinda unique fat shaped plastic version unlike 3.5L version which you can see the actual thermostat.
I don't have temperature issue or any codes, but my car is very low mileage per year, so it will be slow to show..... if indeed my thermostat is not currently mineral free and is not opening a 100% when and if it should. Hmm.

 

Good to hear it is ok now. Happy miles!