Oil burning smoke on cold start up

[Toady1]

I've just been to view a crazy quick stg2 C6 RS6, it's done 104k miles. On start up it smoked a fair bit for say 5-10 seconds (almost like valve stem seals), I didn't see which side pipe it exited from, could have been both. But once warmed up it was fine, and I didn't notice any oil whilst driving. Is this likely to be the turbo's? Its only recently been MRC'd and apparently they told him its fine. It sure went like a missile and no signs of any problems on the test drive, it was just on initial start up.

I've searched and came accros some posts, but it doesn't seem to be that common. It is definately oil burning, not moisture as it was blue. It hadn't been started for 2 weeks according to the owner.

[Toady1]

No one else come accross this? I was thinking it was seals in the turbos passing oil when stationary into the inlet tract.

[Jim Haseltine]

Mine does that occasionally. Last night I started it for the first time in 5 weeks or so and had a bit of smoke for 10 seconds or so. It would also cough a cloud out if I booted it which I hope was down to the prodigious amount of oil in the intercooler pipes - I'd estimate that there was best part of half a litre in them, can't be certain because most of it missed my catch tray.

[Toady1]

I've since been told that it didn't smoke on start up this morning, but I wasn't there! I've also managed to contact a previous owner who said it had had the valve stem seals replaced under Audi warranty as it smoked on him on iniotial start up, this was over 4 years ago. He also said they have a dry sump which keep some oil in the top of the engine which over time can let it seep into the combustion chambers hence the puff of smoke. It was literally for 5 seconds or so, and not a considerable amount of oil.

[rs6danbar]

Mine smoked some mornings ago for few seconds. Not too concerned about it.
Tho I've experienced both turbo failures, never seen so much smoke poruing out and exhaust before, literally filled 3 lanes on the highway when it happend.
I reccon all turbo cars at somepoint ends up having oil in the intercooler so you're probably fine.

[Jim Haseltine]

He also said they have a dry sump which keep some oil in the top of the engine which over time can let it seep into the combustion chambers hence the puff of smoke.

I'd take 'dry sump' being the reason with a pinch of salt, some oil sits at the top of every engine and over time finds it's way to all sorts of places if the engine isn't used. If the smoke was only for a few seconds after it had been parked up for a while I wouldn't be concerned about it.

I reccon all turbo cars at somepoint ends up having oil in the intercooler so you're probably fine.

Non-ballbearing turbos have bush bearings which use a film of pressurised oil to separate the bearing from the turbo shaft. The oil gets into the charge by misting past the turbo seals (which aren't a seal as we'd understand them, they're like a sort of piston ring), the intercooler then does it's work dropping the charge temperature so the oil condenses out on the 'cold' side of the cooler.
At least that's how I understand it.

[Toady1]

He also said they have a dry sump which keep some oil in the top of the engine which over time can let it seep into the combustion chambers hence the puff of smoke.

I'd take 'dry sump' being the reason with a pinch of salt, some oil sits at the top of every engine and over time finds it's way to all sorts of places if the engine isn't used. If the smoke was only for a few seconds after it had been parked up for a while I wouldn't be concerned about it.

Well I went to view the car again today tested that the engine was stone cold, I got the guy to start it whilst I watched the exhausts and both were perfectly fine, well black soot came out but that was just unburnt fuel, and as it's a stg2 car it had no cats to prevent this too. I also gave Grizz from Unit20 a call and he said if they've not been started for a while like this one had been then it's quite normal for them to smoke a bit, even though I said it was blue burning oil smoke. He even said his one did when it was tuned and relatively new!

[ATinOf]

Mine used to chuck out a load of smoke but only when I was pushing it down the motorway, I mean really pushing it. Since I did the work on my gearbox and engine its as clear as a bell now.

I did a few things to it while the engine and box was out so I couldn't categorically say which was the root cause but if I was to put my finger in the air to guess at most likely I would say either the oil sitting in the offside intercooler hose being drawn into the engine, or the vacuum pump oil seal to the chain casing chucking it onto the exhaust

If youve got half a litre or so of oil in that intercooler pipe and its not seen the light of day for 40K miles or more I wouldnt worry about it (but obviously clean it!!); its likely from the PCV vent system over time. If youve got oil in the nearside lower intercooler hose, Id be looking for where its coming from

[ATinOf]

Personally I've added that intercooler hose clean out as an activity on my 10K service interval check list; so I can keep an eye on it

[Jim Haseltine]

Started mine again on thursday evening - no smoke. You can't tell if there's oil in the cooler pipes by squeezing them - I though my right pipe would be pretty empty because i couldn't feel anything but when I pulled it off the inter cooler the stuff went all over the place, the oil that missed my catch tray formed a pool about 18" in diameter. There was a good 250-300mL in the left pipe.

[Toady1]

Where does the oil come from though? I don't own mine yet but i'm always tinkering so I'll investigate at some point.

[Jim Haseltine]

As above. Some mists past the turbo shaft seals, the rest is from the crankcase beather. Logically, you'd expect the cooler inlet pipes to be a little greasy inside and the outlets to contain liquid oil but the coolers on our cars flow from the bottom upwards so oil that condenses at the top of the coolers drains down to the inlet pipes.
Oil in the coolers isn't unique to the V10, all turbo engines do have it - for instance, unless it's force cleaned with solvents an intercooler from an Ur quattro (which has an engine half the size of the V10) can take months to drain.

[Stiggles]

As above. Some mists past the turbo shaft seals, the rest is from the crankcase beather. Logically, you'd expect the cooler inlet pipes to be a little greasy inside and the outlets to contain liquid oil but the coolers on our cars flow from the bottom upwards so oil that condenses at the top of the coolers drains down to the inlet pipes.
Oil in the coolers isn't unique to the V10, all turbo engines do have it - for instance, unless it's force cleaned with solvents an intercooler from an Ur quattro (which has an engine half the size of the V10) can take months to drain.

I knew I recognised your user name!!!

Fellow quattroforum member here

I get a large quantity of white smoke regularly on cold starts, I'm pretty sure it's just condensation though! It disipates once the revs settle down to normal idle.

[Jim Haseltine]

White smoke on a cold day - I get loads until the idle drops, on a cold winter evening my car can hide a couple of our HGVs behind a pretty good smoke screen. And yes, having stood in the cloud a couple of times, it's condensation - no smell of oil or antifreeze.

[pete2144]

He also said they have a dry sump which keep some oil in the top of the engine which over time can let it seep into the combustion chambers hence the puff of smoke.

I'd take 'dry sump' being the reason with a pinch of salt, some oil sits at the top of every engine and over time finds it's way to all sorts of places if the engine isn't used. If the smoke was only for a few seconds after it had been parked up for a while I wouldn't be concerned about it.

Well I went to view the car again today tested that the engine was stone cold, I got the guy to start it whilst I watched the exhausts and both were perfectly fine, well black soot came out but that was just unburnt fuel, and as it's a stg2 car it had no cats to prevent this too. I also gave Grizz from Unit20 a call and he said if they've not been started for a while like this one had been then it's quite normal for them to smoke a bit, even though I said it was blue burning oil smoke. He even said his one did when it was tuned and relatively new!

Yeah I have Martins old car and yes it smokes on start up a bit, but clears after a few seconds, I don’t worry to much about it...


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