Thin white vapour like smoke on cold days

clk320-

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Oct 26, 2016
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41
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CLK320 2003
On cold days like today there's a thin misty like white smoke coming out of the exhaust on my clk when idling
Nothing while driving and nothing on warm days
Only happens when cold

Is this normal? The outside temperature is 11C as shown on the dash.

Worried it's head gasket but check under oil cap clean as a whistle. Coolant level is perfect, and oil is clean.

I find this way to talk to other owners brilliant! All as interested in Mercedes Benz as me!!
Thanks so much
 
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clk320-

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Oct 26, 2016
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Car
CLK320 2003
Update just saw a 2011 plate CLS and at the traffic lights it releasing the same kind of smoke. Surely this mean it's normal and a relatively new car like that's won't have any major engine damage?
Cheers
 

MancMike

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It's steam. Just water vapour you're seeing. Just like your breath, it's visible on cold days.
 
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clk320-

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Oct 26, 2016
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Car
CLK320 2003
Do you think it may be something wrong with exhaust?
Just parked up car and there's a ticking noise from the exhaust... could this be a catalytic converter on way out? I have a feeling it's because previous owner for 3 year ran 95RON petrol in it when it's recommended to run premium?
Thanks
 

The Dude

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1995 R129 320 SL, Volvo C30, Porsche 996, Honda Jazz Sport
...probably just the exhaust cooling down, this makes a ticking sound...cats rattle when revved not when car is turned off...nothing to worry about...
 

PobodY

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CLK350 Sport, Nissan GTiR
As above; nothing to worry about.

When it's cold outside you'll get condensation from the exhaust; that might be more noticeable with a larger bore tail pipe (as it "puffs" out gently rather than "shooting" out of a smaller pipe).
If the pipe was starting to warm up (and expand) then it will make noises as it cools again (and contracts). - It may well be that this is more noticeable from the catalytic converter as the monolith inside it will have a different thermal expansion coefficient to the metal around it.
 

renault12ts

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Mar 5, 2009
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16,175
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2005 W215 CL500.
Do you think it may be something wrong with exhaust?
Just parked up car and there's a ticking noise from the exhaust... could this be a catalytic converter on way out? I have a feeling it's because previous owner for 3 year ran 95RON petrol in it when it's recommended to run premium?
Thanks
Did you actually read post#3...you thanked him in post#4?
 

MancMike

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Jul 29, 2014
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There's nothing wrong with your exhaust.

Water (H2O) is actually produced by your cat, and so the steam coming out proves it's working perfectly. The cat runs at several hundred degrees (850C-ish) and so the steam will condense in a cold pipe and drip out, until the entire cat-back is up to temperature, then it'll just poof out like you're seeing.

See diagram of the magic your cat is performing;
 

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