CLS 350 CDI -Puff of Blue Smoke on Startup After Standing

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E55BOF

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I took the 2013 CLS 350 CDI in to Terry Gates for a health check yesterday. All fine, no codes, no sign of oil leaks (so the oil cooler seals aren't leaking yet, but they almost certainly will sooner or later...), replaced the duff thermostat and it now holds 90 degrees as it should. The MoT test emissions show that the garage needed four tries to get it through, and it only just passed even then, but I suspect that was because of the low coolant temperature - it was 60 degrees, no higher, on test.

The only slightly worrying thing is that there's a puff of blue smoke on startup after it's been standing overnight. My first thought was valve stem oil seals, but when I mentioned this to Terry, he told me he's never had to replace them on an OM642 which has been properly serviced, and this one has. It's definitely not drinking oil, and there's no smoke at any other time.

Is it possible it had to have the nuts revved off it to get it through the test, and an oil seal has been slightly damaged? I've also seen mention that the top-end engine breather can play up; could that possibly be the cause of the problem?

I don't know much about diesels. Should I be concerned?
 
Now that the thermostat has been replaced and the engine is running at the correct coolant temperature, the little puff of blue smoke seems almost to have stopped. The car needs to stand for four or five days to be sure, but at worst it can't be more than slight seepage through the valve stem seals, so I'm not much worried.
 
We need an 'embarrassed' smilie... There never was a puff of blue smoke; it's just unburnt atomised diesel, and it's quite common with the OM642 on a cold start. The previous owner but one of the car had the same thing.

So why did I think it was blue? Simple; I've just had one of my pairs of glasses relensed, and the new lenses came (to my surprise) with a rather more pronounced blue tint than the old. Guess which I was wearing when I noticed the 'problem'? :doh:

As I said, we need an 'embarrassed' smilie...
 
We need an 'embarrassed' smilie... There never was a puff of blue smoke; it's just unburnt atomised diesel, and it's quite common with the OM642 on a cold start. The previous owner but one of the car had the same thing.

So why did I think it was blue? Simple; I've just had one of my pairs of glasses relensed, and the new lenses came (to my surprise) with a rather more pronounced blue tint than the old. Guess which I was wearing when I noticed the 'problem'? :doh:

As I said, we need an 'embarrassed' smilie...
As far as updates go.......priceless! ;) :thumb:
 
Hope you haven't told the wife/partner she is looking a bit 'blue'
 
Morning all,

Just registered myself on here as I have got definitely blue smoke coming out on a cold start first thing in the morning…

The car is under warranty with Mercedes and to date I have had replaced the DPF as it was smoking black on the hard acceleration and separately a new ECU as it kept going into limp mode.

It’s a 2013 350 CD I CLS with only 34,000 miles on the clock. When I bought it in June 2020 it had only covered 17 K in seven years!
 
Morning all,

Just registered myself on here as I have got definitely blue smoke coming out on a cold start first thing in the morning…

The car is under warranty with Mercedes and to date I have had replaced the DPF as it was smoking black on the hard acceleration and separately a new ECU as it kept going into limp mode.

It’s a 2013 350 CD I CLS with only 34,000 miles on the clock. When I bought it in June 2020 it had only covered 17 K in seven years!
No smoke gets through a regenerative dpf , what you will have are cat type diesel particle catchers . If your tail pipes are sooty = no dpf .
 
No smoke gets through a regenerative dpf , what you will have are cat type diesel particle catchers . If your tail pipes are sooty = no dpf .
Yes tail pipes get a little sooty..... I’m sure the dealer said they replaced the dpf?? It’s a 2013 350 CDI CLS mk2. I’m not mechanical at all! Maybe I misheard!? But it did cure the smoking on acceleration and only recently am I getting this puff of blue black smoke on start up first thing in the morning when the engine is stone cold
 
Yes tail pipes get a little sooty..... I’m sure the dealer said they replaced the dpf?? It’s a 2013 350 CDI CLS mk2. I’m not mechanical at all! Maybe I misheard!? But it did cure the smoking on acceleration and only recently am I getting this puff of blue black smoke on start up first thing in the morning when the engine is stone cold
The inside of the exhaust pipes on a dpf equipped car like yours should be clean metal
 
The inside of the exhaust pipes on a dpf equipped car like yours should be clean metal
There are a bit dirty anyway due to car needing a wash but you can see black inside...😳
 

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There are a bit dirty anyway due to car needing a wash but you can see black inside...😳
They look like my non dpf E320cdi :( . Maybe give them a good clean first , if they soot up you have a problem . When is your mot ?
 
They look like my non dpf E320cdi :( . Maybe give them a good clean first , if they soot up you have a problem . When is your mot ?
Last time I cleaned them they came up as new on the outside but still sutted up on the inside... mot was done last month and no advisories, straight pass
 
Last time I cleaned them they came up as new on the outside but still sutted up on the inside... mot was done last month and no advisories, straight pass
my understanding is that 0% of black soot goes through a dpf ? Hopefully someone who knows what they are talking about will add something useful .
 
my understanding is that 0% of black soot goes through a dpf ? Hopefully someone who knows what they are talking about will add something useful .
Need to find out then if I have a dpf or not then!?
 
I've had 3 cars with DPF. All 3 have had minor sooting on the exhaust pipe. The only other one I looked at closely was a mates 2014 Scirocco diesel (don't ask), and we had to get the Autosol on the exhaust tips to give them a good clean as they had never been cleaned.

So I would say some minor sooting on DPF exhausts is normal in my experience. But nothing like the sooting that my dad's 2004 Volvo D5 gets.
 

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