Blue Smoke: A Cold Tartar Recipe

Hi,
I have the following problems with my TDI AFN 110 hp engine, which has 118,000 km (approximately 73,000 miles) on it:

Approximately 3,000 kilometers ago, I experienced a timing belt failure, which resulted in damage to all the exhaust valves. I also replaced the valve stem seals at the same time.
The vent valve was also damaged during the disassembly, and I had to replace it.
'Since then, I've noticed that I need a lot more oil (before, I didn't use any oil every 15,000 km, but now I'm already using 1 liter after only 2,000 km!). During cold starts, I've noticed that the engine is producing unusually blue smoke. I'm using 5W30 Castrol oil provided by my employer, BMW, but that's what I was using before as well. However, it still doesn't seem to be enough. When driving normally in the city, there are no visible signs of smoke, but when I drive on the highway and accelerate hard, the engine smokes. It's difficult to say for sure whether the smoke is blue or black. The smoking doesn't really go away even after 20 km of full throttle, and now I'm starting to get seriously worried!!!'

'As usual, there are no error codes stored, and I can also rule out a problem with the fuel injection start. It's probably normal for a diesel engine to produce a small amount of smoke. What other potential issues could be causing this?'

Thank you in advance for your answer.

Is your car running poorly somehow?
Does the engine have less power?


Perhaps the turbocharger is faulty and needs oil?


Best regards,
Ralf

Hi,
I'm risking causing harm to you or the person carrying out the work, but did you protect the valve stem seals with a plastic sleeve before assembling them, to shield them from the sharp edges of the valves?

Hi.

'I'm sure I didn't do anything wrong during the assembly; at least, nothing is left over *g*. I've certainly done this before.'
I can rule that out. Just like the loader.
Okay, it whistles a bit, but that's not a big deal. Unfortunately, I can't detect any loss of power or anything like that (thankfully), except for a slight 'power dip' as I've described before.
This was also the case before I had the meniscus injury.

'Also, none of the errors listed in the database seem relevant, except for the nozzles, which I will personally check this week.'

oh... I accidentally logged into a friend's account... but it's okay .

Best regards, Daniel (g1om)

Well... I would have also immediately suspected the shaft seals, since it seems to be smoking, especially when starting the engine. Otherwise, I'm not sure what else it could be.

Okay, now I can describe it in more detail. It's definitely black smoke, and this is happening in the city, at around 3,000 RPM.

Could it maybe be related to the nozzles? What do you think???

Thank you for your reply.

g1om wrote:

Could it perhaps be related to the nozzles? What do you think???

Hi,

We have discussed this topic several times in the forum. I think with this specific LL (likely referring to a specific engine model), the nozzles are probably not the problem. Let the engine run in neutral for about half an hour. If, after revving it up (under load) for a minute, thick blue smoke comes out the back, you know that oil is entering the combustion chambers -> so maybe it's the valve stem seals after all. Smoke at 3000 rpm also suggests problems in the area of the EGR (Exhaust Gas Recirculation) system, etc.

Well, that's the case, but it's not blue smoke; it's black smoke. I experience the same thing when I drive in the city for a long time; then it just shoots out a cloud of smoke, and it's really intense.

'A minute might be a bit of an exaggeration, but yes, it could be. I'll test it again. Thanks for the tip.'

'The AGR (Abgasrückführung) has been dead for a long time; it's completely closed, and I have a plate installed to prevent anything from entering it. I took it out today to test how the engine behaves with a functioning AGR, but there's been no improvement in the smoke emissions.'

However, what was unusual was that the plate was so full of oil and soot that I almost thought the turbo was leaking. Well, I'll definitely keep an eye on that.

Hi,

That sounds like a classic case of piston ring seizure followed by valve sticking. Your exhaust valves have been permanently deformed , and the force required to overcome this had to be applied by the pistons. They are made of lightweight metal and have certainly suffered, meaning they have been compressed. If the collision was strong enough, this compression extended into the ring area, where the piston rings sit in their grooves with a very small axial clearance (a few hundredths of a millimeter). If this clearance is reduced, the rings become stuck, and they can no longer seal properly. You might not notice this in the performance, but oil will seep in between. This means either adding oil or an engine rebuild (ATM ).

Best regards, Uli.

You're right, a friend of mine, who is a mechanic, said the same thing today.
It's been for 30 years. He said to remove the pistons and install a new set of rings. If it stays like that, it will be expensive! I couldn't see anything on the pistons at all when I had the head off. Well. Also, the assumption about letting it run for 30 minutes while stationary turned out to be true. If I give it full throttle after that, it smokes blue very intensely!
I also took another look at the turbo, and there's some oil stuck in the pipes. Maybe it's all related?

'It seems that this only happens when the engine is stationary. At high RPMs, the combustion pressure is also very high, so theoretically, I should have the lowest oil consumption.'


Hmm... I'm already really annoyed by this. I'm seriously considering selling the car as it is. It's not ideal, but...

Thank you very much for the great tips you were able to give me.

Okay, I've decided to fix the machine again today, even though it's going to cost a lot of money.

I did the 30-minute test again. Let the engine idle for half an hour. If, after that, when you rev it up (under load) for a minute, thick blue smoke comes out the back, you know that oil is leaking into the combustion chambers. So, maybe the valve stem seals are the problem – you might be right.
I have this case!

Which components can I rule out?

The thing about the turbo is a bit complicated. Okay, fine, I'll just rule it out for now.

Is there a way to determine whether the oil is coming from the cylinder head or the piston?

'My mechanic said it wasn't that the piston wasn't compressing, but rather that the oil scraper ring broke through the oil film during the combustion stroke, and that the ring is now stuck in the cylinder. He said that if it were a stuck piston, I would have immediately experienced a seizure because the piston would have been forced outwards, which I've never heard of before, but okay.'

Do you think I should take the head to an expert to have them examine it carefully after I take it apart?
Before that, however, I want to be absolutely certain that the problem is coming from the pistons.

Hi,

As I see it, the turbo loses a little oil as it gets older, which then accumulates in the intake pipes and appears to be a lot.

Since Turbo didn't make contact with your valves, and everything was fine before, I would investigate the piston theory. It fits the picture and sounds logical.

If you have a lot of time to tinker, you could try to loosen the groove, as it's likely only stuck in one place. Probably just the top ring.

We've already done all of this with gasoline engines, but diesel engines are different - just give it a try.

What I don't understand is this: if the valves are hitting the pistons to the point where the valves are damaged, then you should also see some damage on the pistons themselves.

And while you're at it, check the valves for any signs of oil coke buildup, and see if any of them look particularly bad.

(Is it mean of me to wish you a nice weekend, knowing that you'll be working in the workshop from Saturday morning until Sunday evening?)

Okay, that's fine. The car doesn't bother me as much anymore, considering how much trouble it's already caused *g*.

'That's exactly my problem. I didn't see anything on the piston back then, no marks or anything like that, otherwise I would have removed it immediately. Since all the valve seals are new, I don't think they have any deposits. If the piston were compressed in the upper ring area, I would have definitely heard a loud knocking sound because the combustion chamber would have been pushed outwards. My friend thinks it's just the oil scraper ring!'
'The other rings wouldn't have anything at all. To be honest, I've never heard of anything like that before.'