Milor

Hi,

My 2010 W212 E250 CGI likes to smoke. Every few weeks, while sitting at the traffic lights, engine at operating temperature,
I can see some smoke coming out through the front grille. Lasts for about 5 to 10 seconds and then stops. I pull over to
inspect, but cannot see ANY sign of leakage of coolant, oil or petrol.
I think that the smoke looks more like water vapor rather than oil or petrol smoke.

I have taken all plastic panels from underneath the car, inspected very closely every possible place in the engine bay, but
everything is dry. No oil leaks or anything. The car has done 78000km.

Any ideas, please?

Thanks

Milo

homeofstone

check valve cover closely to see if a small amount of oil is leaking then is burned off on the exhaust manifold.

GuestFromTampa

+1 on valve cover gasket

KEY08

Where do you live? Are you experiencing very high temps and your A/C is running overtime? May just be vapor coming off your evap coil that may be freezing up.

Milor

Thanks for your response.
I'm in Australia (Sydney) and A/C is usually not on when the smoking occurs.

Milor

Hmmm.... that was my # 1 suspect, but can't see anything. There IS one little suspicious dry spot on top of the exhaust manifold cover which I've cleaned up not to see whether it gets dirty again.

Thanks.

tresean1

I, too, noticed that on some of my older cars; it would happen when it rained or at night time. When you experience it, what's the weather like? Maybe just some engine parts cooling down quickly?

thefisch

Do you notice any smell associated with the smoke? Water vapor won't have an odor compared to oil. Refrigerant leak from compressor up front would have a loud sound as pressure is released so that's not it.

Given what you found it may just be a small oil leak which can be a nightmare to pin point. Could be the drip is running further back on the engine while driving due to air flow which means the smoke may only be visible from behind. Then when you stop any residual drips onto the exhaust near the front without air flow pushing it back. Obviously need to monitor the oil level and the spot you found. Might help to clean the engine off and see if any new spots appear near any gaskets.

Milor

The steam issue. I have noticed that it always appears in the morning. Sometimes even before the car
reaches working temperature. It can occur 5, 10, 15 minutes into the trip, but never over 20 mins. I
could be wrong, but it seems to be happening on same mornings when there is a lot of evaporation from
the exhaust. Mercedes has pressure tested the cooling system, no probs found. I even wrapped a white
cloth around the coolant expansion tank cap to see whether it's coming from there. Nope. No oil dripping
or burning anywhere. Mercedes is checking the issue for the third time in the past year at the moment.

Have a look at the YouTube video, please.

https://www.youtube.com/watch?v=SGSm...ature=youtu.be

Thanks

Milo

Sunnyslope48

Is there dew or moisture on the car's exterior when this happens? Is car garaged or kept outside? More prevalent when it has been raining?

Milor

Yes, mostly in winter it seems when there is dew on the car's exterior. Mostly when the car is not garaged overnight, but it can happen even if garaged. Usually at
the same time when there is evaporation from the exhaust, but sometimes even once the exhaust evaporation has stopped.

Sunnyslope48

Might try wiping the moisture off the car hood in the morning and see if that stops it. I THINK it's just the engine warming up, raising the temp of the dew on the hood in the cold air, and you see some 'smoke' or water vapor.

Milor

Hmmmm... thanks for that..... just got me thinking. Maybe there is some dew on the UNDER SIDE of the hood which eventually gets burned off. I might have to check that out. I'm losing
my mind over this. Even Mercedes can't solve it (maybe because it's still under warranty ... haha).

ItalianJoe1

Very possible there is moisture sitting in the radiator fins and when it finally opens the thermostat and warms up it boils it off?

Milor

Very possible that water is pooling somewhere..... Good idea!

NachoLibre

This could also be caused by the radiator fan not starting at correct temperature. If the radiator is getting overheat the steam vapors will come out from front grill.
this happen to me twice on 2 different cars.

KEY08

Milor

If the radiator is getting overheated...... what is the liquid that is evaporating? Where does it come from?
Thanks

rohanpatel14

ItalianJoe1

Fix your oil leak. That will drip on the exhaust and smoke.

thefisch

I agree on fixing the leak, but if it was oil burning you'd notice the smell too. Hopefully you can park and get out the car safely to inspect this further when it is happening.