Heavy Smoking

[Phil]

I queried this before but didn't get to the bottom of it, so apologies if anyone has a moment of deja vu! I was doing radio on the McRae Stages on Saturday and spent about 4 hours parked up with the engine running. When I drove off a huge cloud of dense white smoke came out of the exhaust and the car kept smoking for about half a mile. This seems to happen whenever the car sits idling for more than about an hour in cold, damp weather. The vehicle's an '02 110 Td5 and otherwise runs faultlessly.

Does anyone know why it smokes? I don't know another that does!

Thanks,

Phil.

[FridgeFreezer]

A lot of diesels will do this if left idling for hours, our work transits do it when the guys are working by the roadside all night, sounds like a piston is about to fly out a quick blat up the motorway and they're back to normal.

[Phil]

Interesting, thanks, similar although mine only smokes; the engine sounds perfectly normal.

Do you know what causes it? It does tend to alarm anyone in the vicinity

[hoarebag]

Condensation in the turbo/exhaust as it's not hot enough when it's idling which is then vaporised when you give it some stick? Or some incomplete combustion of fuel in the bores which the burns off when you set off again. You'd expect white smoke if there is insufficient fuel for the air provided so i don't think that works either.

A mystery to be sure.

[JimAttrill]

It doesn't do to leave a diesel idling for a long time. It glazes the bores, so I am told. OTOH I have no personal experience of this so it could be bullSh1t. Just something I was told. ....

[110_USA]

It doesn't do to leave a diesel idling for a long time. It glazes the bores, so I am told.

I don't know about the differences between big semi-trailer engines and smaller diesels but I've got a few friends who drive them for a living and will let them idle while they're sleeping, 8 hours or so, to run the A/C etc. Seems to be a common practice, sometimes the trucks go days without being shut off. I'll ask if there is suppose to be a negative effect but I would doubt it as they do a million miles or more.

[Phil]

When I wore a green suit to work it was common for radio vehicles to sit for hours with the engine idling, they were 2.5NAs. I don't remember them smoking in the same way nor any suggestion it was bad for the engine (although that wouldn't have been a concern to anyone anyway!).

I can't find anything which would account for this and there's nothing to suggest it indicates a fault, but it's disconcerting to say the least!!

A mystery indeed.....any other suggestions?

[Mo Murphy]

I'd be inclined to say water vapour from the exhaust.

Mo

[Phil]

Mo, I understand your thinking, however, the volume and density of the smoke seems greater than likely from vapourising condensation in the exhaust.

I was looking for a picture to illustrate and thought to find one of a Challenger popping an L8. The magic of the Internet reveals that "the Challenger 2 can also create smoke by injecting diesel fuel into the exhaust manifolds".

Is my Td5 doing something similar?

[Mo Murphy]

Hmm, what does the smoke smell of ?

I'd still be inclined to go for condensation. Water volume expands by 1600 times to create steam, so a relatively small amount of water can go a long way.

Good luck with tracking it down, it may be an idea next time to go a 100 yards down the road to get it billowing and then stop and get a friend to rev it whilst you examine the smoke at the tailpipe.

Mo

[ThreeSheds]

My vote goes with Mo on condensation theory. Although mine's a V8, both types of engine produce a fair amount of water in combustion products and my RRC often sits idling for a while (I just can't resist running it while I clear my tools up) and after a few such sessions, it can be heard bubbling in the exhaust.

On mine there is a low point in the exhaust just behind the rear axle which obviously fills with water. This probably wouldn't be so noticeable apart from the fact that I have removed the last silencer which normally sits just behind this point - with this silencer removed (and a side-exit exhaust) a blip of the throttle will easily spit out a litre or so of water over 5 metres (!!) across the garden . The first time I noticed this was when I drenched the welder, but now I clear the tools and make sure the dog is safe before running it.

Anyway - I am thinking that I can never quite clear the water by blipping, and that if I went for a proper drive and got the exhaust HOT as opposed to warm (or if the water-trap was closer to the engine and so more quickly affected by it's heat), then this standing water would generate quite a lot of steam... I am prepared for this when it get's it's first drive (to the MoT station) in a couple of months time so I won't panic - but the same thing might apply here???

Rog

[Phil]

Mo and Rog, many thanks to both of you; I hadn't realised the amount of expansion involved nor the possible quantity of water The condensation theory now seems much more likely to explain what's going on. I am puzzled as to where the water might gather and why my vehicle seems to do this when others don't..........

Phil