Black sludge and grey smoke

Last year I ran my 1997 300Tdi on new veg oil 50/50 with diesel for about 6 months. Since going back to pure diesel I have noticed quite a bit of greyish smoke from startup until the turbo kicks in and it seems down on power. I changed the engine oil and filters at the weekend and it was very black (25000km since last change) and quite thick. Looking inside the filler cap the rockers had a lot of black deposits and there was a layer of sticky black crap stuck to the inside of the filler cap.
It has never overheated as long as I have had it (2 years) and the only issue I have had that was oil related is as follows:

I took it in for a clutch change and, after I picked it up I was driving home and it seemed quite lumpy and lacking in power severely. I slowed down and pulled over just as the engine died. I restarted it and pulled away when the engine started over running, I had to stall it to stop it. I drove straight home (2 miles) and had a look at the dipstick, not a drop of oil. I dont know how that happened, whether it was the garage (would you lose engine oil doing a clutch?) or just bad luck but it has been smoking ever since that.

Any ideas whats up with it and how to fix it? I am minded to run some engine flush through it and change the oil again but apart form that I am stumped.

Have you look in the intercooler hose?

Has it had an EGR removal?

I removed the EGR and blanked it off some time ago, I will check the intercooler hoses in the morning as I need to do some work ATM but last time I had them off there was a light coating of black oil inside, nothing too much.

marcd said:

I changed the engine oil and filters at the weekend and it was very black (25000km since last change) and quite thick.

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25000 Km = 15625 miles Recommended oil change interval for 300tdi is 6000 miles (about 9600Km)

Good chance your turbo seals have gone and running on its own oil. Be very careful as engine could run away to self destruction if not sorted prompt!

When running veg you need to do extra oil changes, this is because in a cold engine veg can get past the piston rings and into the oil.
Once veg gets into the oil it causes polymerization and the oil turns to jelly if left too long.

It can also cause ring gumming (piston rings stuck to the piston causing low compression), this will speed up the polymerization and also give low engine compression, lack of power, high oil consumption and poor starting.

All this will ad up to what you are seeing.

If it's not to far gone you may be able to fix it with water injection (google it).

I doubt the turbo seals are gone, it had a recon unit about 35k miles ago, or could they fail that quickly?
I will have a look at water injection, thanks.

Also, the over run thing only happened twice and now she is behaving fine, apart from the smoke and black gunk.

Ok, here is this morning'g update.

I had a look in the inlet and outlet pipes at the turbo and found a little oil in each pipe, not loads but a dribble. I had a feel in the intake side of the turbo and there was about 1mm of play from side to side, none front to back. I decided to have a look under the injector pump cover and there was about 5 to 10ml of oil on top of the diaphragm.

To me this suggests that the turbo oil seal is on the way out, am I right?

I suffered a turbo failure about 2 years ago and had a recon unit fitted by a local garage, is it likely that the seal will have failed this quickly?

Finally, would refurbishing the turbo be sensible or is replacement a better option?

25,000KM TSK TSK you naughty boy! Am I the only one who changes his 300tdi's oil every 3k? (considering that our hot, dusty climate combined with short distances is considered to be "extreme use")

I know, it will be more frequent in future to be sure.

I am thinking outlet side oil seal failure, anybody have any other opinions?

Just thinking out loud, could the cyclone breather be to blame? I have never cleaned it out and I do not know how long ago it was done by the previous owner (MOD).

Cleaned the cyclone and its a bit better. I left it running for half an hour and when I came back to it I noticed a small pool of oil under the exhaust.
Does this support the turbo oil seal failure theory?

Turbo will have a little radial freeplay as the shaft normally floats in oil when engine is running but there should be no axial freeplay so you may be ok. Trouble is if the oil had thickened then it may not have been lubricating the turbo (amongst other things)properly. Plus with 'thinner' oil in it now there is a chance that oil can find its way out the engine easier!

Yes, it is smoking more since the oil change.

marcd said:

Cleaned the cyclone and its a bit better. I left it running for half an hour and when I came back to it I noticed a small pool of oil under the exhaust.

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If that is dripping out of the exhaust itself you could be in for a would of pain.

A world of pain as in what?
Head gasket?
Or worse?

Engine runaway and self destruction if it ends up burning its own oil. Youtube diesel runaway

marcd said:

A world of pain as in what?
Head gasket?
Or worse?

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It could be a cracked head leaking oil into the exhaust port,
excessively worn piston rings/bores, gummed rings,
or if your lucky just a head gasket.

To find out you can do a compression check, then pore a few ML of oil in each cylinder and repeat the check, if the compression is higher with the oil then the rings/bores are the problem.

What ever you do you'll need to remove the exhaust system and clean all the oil out before driving on the road, if you don't when it gets hot it'll smoke like hell until all the oil is burnt off.
Until then you'll never know if you've fixed the problem, and if you haven't your in danger of a runaway without any tell tail signs before hand.

Hmm..ok, I will try and get that done this weekend.
Yesterday I took the hose off from turbo to intercooler and ran the engine for a minute, quite a bit of oil was blowing out of the turbo. There was also some very thin smoke chuffing out of the oil filler cap while the engine was running, is this normal?

marcd said:

Hmm..ok, I will try and get that done this weekend.
Yesterday I took the hose off from turbo to intercooler and ran the engine for a minute, quite a bit of oil was blowing out of the turbo. There was also some very thin smoke chuffing out of the oil filler cap while the engine was running, is this normal?

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You will always get some gasses coming out the filler, but it should not "chuff" smoke.

If not burnt by combustion any oil going past the rings will come out through the turbo so this is not conclusive.
You could remove the exhaust manifold and see if it's oil going into the turbo or just coming out, this would at least give you more of an idea of what is going on.