Oil Mist in Intake: Causes & Solutions

Hello!

I recently bought a Lancia Delta 1.9 TD (9 years old, 165,000 km).
While replacing the air filter (which was quite dirty), I noticed a slight oil mist inside the filter housing and in the intake pipe (the engine had been running shortly before). The old filter was coated with a thick layer of soot and oil on the turbocharger side, but I have no idea how long that buildup had been accumulating.
I read here that it's normal to have oil vapor in the intake system, and I'm going to wait and see about the filter for now.

My problem is that I hear a quiet to moderate bubbling sound when accelerating, especially in low RPM ranges (like the sound of sucking through a straw from a nearly empty glass).
Could it be that oil mist has condensed in the automatic transmission fluid (ATF) over many years, accumulated there, and is then drawn in during acceleration due to the turbocharger's boost pressure, creating a gurgling sound?
Is it possible to open or empty the LLK (likely referring to a liquid-filled container)? Can this be done easily by oneself, or does it require a professional?

Thank you in advance for your answers!

Regards,

Olli.

lanciabesitzer wrote:

My problem is that I hear a quiet to moderate bubbling sound when accelerating, especially in lower RPM ranges (like the sound of sucking through a straw from a nearly empty glass). Could it be that oil mist has condensed in the automatic transmission fluid (ATF) over many years, accumulated there, and is then drawn in during acceleration due to the turbocharger pressure, creating a gurgling sound?

IMO, it shouldn't make a difference how high the boost pressure is.

Because an engine essentially always draws in the same volume of air (only the density changes with boost pressure) -> the airflow required to produce the "burble" sound is therefore only dependent on the engine speed.

If the bubbling sound only occurs under load (i.e., with boost pressure), I would suspect a leak in the "suction" pipe area.

Hmm... so, between the turbo and the air filter?

The area is actually quite straightforward; it's only designed for the blow-by gases to enter. I can't imagine how such large amounts of oil could get in there.
Or where exactly do you mean when you say 'intake manifold area'?
Where else could that noise be coming from?
It's not actually losing oil, and it's not consuming excessive amounts either (as far as I can tell after about 1,500 km).

'There's also quite a bit of oil leakage near the hose connecting the turbo to the intercooler, right at the connection point to the turbo. Since I tightened the clamp, it's been contained, but it's still leaking a bit. I might take a picture sometime; maybe that will help.'

Regards,

Olli.

lanciabesitzer wrote:

Hmm... so, between the turbo and the air filter?

No, between the charger and the motor.
It's also referred to as an intake manifold at VAG, although, in my opinion, it should more accurately be called a pressure manifold.

Okay, I need to check that out sometime.
Where exactly could this leak be?
Could this be a bigger problem?
I got the idea about the intercooler because the pipe between the turbo and the intercooler is made of plastic, and the bubbling sound doesn't sound like a metallic bubbling sound (which you'd expect from a turbo motor with a metal pipe).
Could it be that something is getting thrown into the pipe when the turbocharger is spooling up?

Regards,

Olli.

I read somewhere online about someone else who was experiencing the same noise (also in a Delta system), and they were told that it might be air trapped in the heat exchanger.
Upon closer inspection, the bubbling sound seems to be coming more from the heating system, meaning it's heard more clearly inside the car than directly next to the engine.
Can the heat exchanger be bled to remove any trapped air, or is that not a significant issue?
Actually, it doesn't bother me, I just don't want anything to break.

Sure, here is the translation of the text from German to English:

'Hello'

Olli.