The magical smoke machine

[Dan]

Hi guys,

Got a slight problem on my hands. I brought the S2 down to my dad's last year and it arrived pushing out smoke. Anyway, finally got around to doing something about it.

Intially thought oil, but it's not using any. Plugs are dry, no smoke out of the oil cap and compression tested fine.

Then thought head gasket / water, but it's not bubbling in the header tank nor any other evidence.

Then realised that the smoke seemed fuelish. Plus the plugs are sooty. Thinking overfuelling?

Can't seem to find the cause, though. It just started doing it one day last year.

Had VCDS on it and there are no engine fault codes. All operational tests performed succesfully.

VCDS reports lamda as around 1 and all other values, as far as I can see, are within usual ranges, as per: http://www.s2central.net/vagcom_4.ht...uring%20Blocks

N75, wastegate, turbo, all seem to be working -- can't find any boost leaks -- so it should be getting all the air that passes the MAF.

Running out of ideas here, so...

Cheers.

[AndyP]

What colour is the smoke? When is it smoking, under load, idle, over-run?

[stocious]

check fpr pipe maybe? wiggle maf plug. 45 deg hoses under isv ive seen spit on a few, hard to see until removed, good luck

[Dan]

What colour is the smoke? When is it smoking, under load, idle, over-run?

Smoke appears to be light grey.

Starts smoking about 20 seconds after striking up. Gets heavier when revving up and then remains fairly heavy on idle.

Ta.

[Dan]

check fpr pipe maybe? wiggle maf plug. 45 deg hoses under isv ive seen spit on a few, hard to see until removed, good luck

Checked MAF, seems fine, cleaned the connection there.

How can I test FPR pipe?

Ta.

[SteveH]

Valve stem oil seals would produce smoke on startup and idle. PCV hoses blocked, turbo seals?

[Dan]

Valve stem oil seals would produce smoke on startup and idle. PCV hoses blocked, turbo seals?

Checked PCV, that's fine. Turbo isn't perfect, but not leaking enough to cause that amount of smoke.

Considered valve stems -- just trying to rule everything else out first =/

Also, smoke doesn't seem oily, not blue and it's not really using any oil up.

Ta.

[stocious]

did you take plugs out ? not sure if you have ? also maybe a bad lamda, an analouge v/meter is good for testing these.

[caterpillar]

checked out the turbo; any play in the compressorhousing... the oilseal at the HOT side are jammed; the the oil are comming out ... then the smoke; and no prob with engine

[JP]

Grey smoke is 90% of the time turbo oil seals. Takes very little oil to create a lot of smoke. Just drop one small drop of oil on your exhaust manifold when hot and you'll see what I mean.

Blue smoke would be stemseals if on startup. On overun and idle it would indicate guides under load rings. The fact the smoke is grey means oil hasn't been burned in the combustion cycle and therefore can only be turbo. Backed up by the sudden onset of the problem and that it gets worse on revving/load.

[Dan]

did you take plugs out ? not sure if you have ? also maybe a bad lamda, an analouge v/meter is good for testing these.

Yeah, have taken plugs out -- they're sooty, but dry, not oily.

Lambda is an idea -- would that show up somehow with vagcom on as excessive lambda "correction"?

checked out the turbo; any play in the compressorhousing... the oilseal at the HOT side are jammed; the the oil are comming out ... then the smoke; and no prob with engine

That's a thought. There is a little play in the turbo. It was still smoking with the coldside disconnected, but obviously if the hotside was leaking oil, that would still happen... odd that it's not using more oil though.

Thanks for the suggestions guys. I'll look into all the above.

[Dan]

Grey smoke is 90% of the time turbo oil seals. Takes very little oil to create a lot of smoke. Just drop one small drop of oil on your exhaust manifold when hot and you'll see what I mean.

Blue smoke would be stemseals if on startup. On overun and idle it would indicate guides under load rings. The fact the smoke is grey means oil hasn't been burned in the combustion cycle and therefore can only be turbo. Backed up by the sudden onset of the problem and that it gets worse on revving/load.

Thanks JP. That makes sense. Sounding more like turbo seals then.

So, turbo off, I guess.

[simons2]

If plugs are sooty and smoke smells of fuel then it is a mixture problem , our turbos use oil pressure to create a oil bearing , some movement side to side is ok , front to back means thrust bearing

[Dan]

So, what's my cheapest option for replacing or rebuilding a turbo?

[djh]

Just get a second hand turbo off the usual people off here, you should be able to get a cheap one to replace yours that way you will know if its that or something else without spending a lot out.