danclements

Hi all.

Just after some advice. Car runs beautifully for 99% of it's duties. No smoke at cold start or any regular driving. When I take it out on the back roads and really beat on it, it starts to smoke. Have been back and forth with a few attempts at fixing it. It appeared to be a trans leak last time as the smoke was from under the engine bay, not from the exhaust. Happened again today and this time we filmed it.

Once the oil temp is over 105c and the big fan kicks in at the engine bay, I get this. Appears to be one of the banks, maybe left side turbo seal. But, I'm no expert. Car still pulls like a beast and runs smooth, despite the smoke. Give it 20mins rest and the smoke is gone.

I've got the word out to my shop and tuner, but any 3rd party advice is appreciated.

https://1drv.ms/v/s!Anl3rKWJWx7Bj9ceVQgHtPacoTFj3A

Thanks.
Dan.

ItalianJoe1

Turbo seals wont leak externally, it will leak through the exhaust. You could have a leak at the feed line on top of the turbo. I've had to reseal a valve cover on an M157 for oil leaks, rare but it happens.

FastWgn

Smell the exhaust when it's smoking to make sure it smells oil and not coolant. Just to be safe. Saying that since you state it starts to smoke when "big fan kicks in" = coolant is getting warm.
You can rule out transmission leak - it would not have a way to enter the exhaust.

danclements

I hadn't even considered the coolant. Swapped out the thermostat just before winter as the fan was kicking in early under soft driving. You could be onto something. Thank you!

Vrodman

I would agree with this theory. While I have not had an issue like this on my 2015, my 2011 (with M156) did have random occasions of smoking. It turned out to be a valve cover gasket. If you see smoke from under the hood, and it smells like burned oil, it is likely a cover gasket leaking in a place that you just can't see.

Good luck.

ItalianJoe1

I have a CL63 in my bay now for an oil burning smell after driving, it has a small leak from the front cylinder head cover, it runs down to the turbo and burns off. Much more common on the 157 than a valve cover as the valve covers are sealant sealed, no gasket, and they rarely leak. The front covers are too, but they are magnesium and the sealant does not seem to stick to them from factory. Once we reseal them one time they don't leak again if it was done right, in my experience.

Osgee

Did you ever find the cause and solution?

danclements

Blown O2 sensor in the end. Running rich on one bank. Happened after a few hard pulls. CEL didn't come on until I got home.