Diesel smoke cloud - normal?

[Marque]

I can cruise around in my E220 CDI all day without any noticeable exhaust smoke. I don't even see any when the engine is cold-started.

Very occasionally, I will put my foot down and then I can see a diesel smoke cloud in my rear view mirror. However, if I repeat the manoeuvre then there is no visible smoke. It's like there is some build-up which is cleared when I accelerate hard. The engine's done almost 70K miles.

Is this normal or does it sound like a problem? The car's going in next week for a couple of warranty issues, so should I mention it?

 

[BlackC55]

Perfectly normal.

 

[st13phil]

This could be complete BS, but I was told a few years ago that soot particles build up in the exhaust system while you're pootling around gently and on the first flooring of the throttle the additional gas velocity blows the soot out - hence the one-off cloud.

I used to take advantage of this if I was tailgated when I had my any of VW 1.9 TDI-powered cars. Casually dropping it into second and flooring the throttle would leave the tailgater in a cloud of thick smoke. It seemed to discourage them

 

[Kompressor_Dude]

My old pug diesel did this too, usually most noticeable at night... when the cars behind you disappear

 

[skemball]

My old barge can lay a good vapour trail for about a mile when i 'clear its lungs' after a hundred or so miles of light cruising.

I get into the habit of giving it a clear-out most times i drive it as it spends its life on cc on the motorway at 2500RPM for mile after mile. I'm sure if i didn't do this it would eventually soot up the cats and silencers and restrict air flow to some degree.

 

[johnsco]

Both our E300TDs do just the same.
It's perfectly-normal.
I agree that a good clear-out every-so-often is a good idea.
It's very easy for cats to get contaminated due to build-up of gunge and soot from a diesel engine.
So - A good clean-out will help to prolong the cat's active life and defer the horrendous costs of renewal.

For the same reason, it's not good to leave your diesel idling with a cold engine.
Better to warm it up quickly and reduce the possibility of cat contamination.

 

[ukcodger]

Yep, CLK 270 CDI does this. Very noticeable if the sun is behind you and you accelerate to pass something after cruising along. it's a real smoke cloud and then...back to no exhaust smoke again.

 

[johnsco]

It's interesting to see from the above comments that the much-more-efficient common-raid diesels are not much better in this respect than my old E300TD with the traditional injector pump

 

[Gareth]

I've not noticed ANY smoke come from my E280 CDI.

 

[rf065]

I've not noticed ANY smoke come from my E280 CDI.

It's the ones behind you that notice it.

Russ

 

[Dieselman]

It's interesting to see from the above comments that the much-more-efficient common-raid diesels are not much better in this respect than my old E300TD with the traditional injector pump

That's because a direct injection engine mixes the air and fuel LESS well than an indirect.
The Mercedes engines with pre-chamber and hot spot vaporise the fuel much better than other engines, hence create less noise and smoke.

Unless your engine is over-fuelling severely it won't clog the Cat, which will never need replacing other than the casing or pipe corroding through.

 

[Uberwagon]

It is also God punishing you for buying a diesel car.

Dave!

 

[davidjpowell]

I never noticed any smoke from my c320. The W210 320 was different though. Only noticed it when Cruise was on at 60 on the A38, going up the steep hill just beyond Exeter and end of M5. I was towing quite a large caravan at the time though!

 

[johnsco]

That's because a direct injection engine mixes the air and fuel LESS well than an indirect.
The Mercedes engines with pre-chamber and hot spot vaporise the fuel much better than other engines, hence create less noise and smoke.

Unless your engine is over-fuelling severely it won't clog the Cat, which will never need replacing other than the casing or pipe corroding through.

Thanks Dieselman.
That's comforting to know.
I've tended to run pretty-old vehicles most of my days - Petrol and diesel - All except one of them have been pre-cat.

One of the things that has worried me about these two E300TDs, is the cost of a cat-replacement, should it ever arise.
You've put my mind at rest.
Thanks
Johnsco

 

[ROBB]

Both our E300TDs do just the same.
It's perfectly-normal.
I agree that a good clear-out every-so-often is a good idea.

especially when en route to an MOT

 

[johnsco]

especially when en route to an MOT

You've read my mind !!