Whistling Noise in 2.0 TDI CR CBBB Engine

Hello everyone,

I've been driving a Passat for about 5,000 kilometers. It belongs to an older lady and is 13 years old, but it currently has around 85,000 kilometers on the odometer.
The engine is a CBBB 2.0 TDI CR with 170 horsepower.

I had the timing belt replaced and performed a major service, including using Liqui Moly engine flush, right from the beginning.
The oil used is Meguin 5w40 Low Emission and it is changed every 10,000 km.
Since the car was originally intended for use with a caravan (trailer), I chose 5W40 to have slightly better temperature stability.

Oil consumption cannot be measured.
Fuel consumption is between 4.8 and 6 liters, as measured in real-world conditions.
Mistakes are not failures.
According to VCDS, the oil consumption is 48 ml.
Differential pressure of the DPF is 18 mbar at idle.
Boost pressure is achieved at approximately 1.5 bar.
The air mass is at full load with an approximate pressure of 1000 millibars per hour.

Now, let's get to the actual problem:
The turbo is whistling, but the turbine spins freely, and there's almost no oil in the intake tract (just a very thin film of oil).
Performance is fully available.
"When I open the oil filler cap and leave it ajar, it wiggles around a bit, but doesn't fall off." --> "In my opinion, this is normal for the 2.0 TDI engine."
"It emits a little smoke, but only when it's hot. I found videos about this on other forums that were considered good."
When you remove the KGE ventilation system, some smoke also comes out from there. So, it's a common occurrence.

When you turn off the hot engine, you hear an air noise similar to that of a turbine running down, but it's relatively dull and voluminous.
I hope it's recognizable in the video.

My question is now:
Is this noise normal? Or what is causing it?
I was still suspecting the bypass valve. --> Is that a realistic possibility?

Or, what can I test to gain further insights?

Thank you in advance. There's quite a bit of text, but I hope to provide all the necessary information.

P.S. You can also faintly hear the noise when you're descending.

Hi,

That sounds pretty normal to me. Possibly the turbocharger isn't in perfect condition anymore, or the compressor wheel might be slightly damaged.

The engine type, like all the diesels I am familiar with, does not have a bypass valve for turbocharger boost pressure.

I would simply check if the compressor impeller and bearing clearance of the turbine shaft are okay, and ensure that no foreign objects can be drawn into the intake system.

If the system is operating at full capacity and there are no unusual power consumption or errors, then what exactly is the problem?

Best regards, Rainer.

Hi there.
"The very quiet noises you hear after turning off the device are normal; I'm familiar with them too. They're caused by air flaps being adjusted, drives being shut down, and the rail pressure regulation system making adjustments."
What's noticeable is the whistling sound when the engine speed changes. Is the timing belt too tight?
hg
Herbert.

Maybe I'm just hearing the fleas cough.
If it sounds normal to you, that's already a good sign.

"The other day, my wife came home and said that the engine stalled while she was driving at about 20 km/h; she must have accidentally put it in fourth gear."
Since then, she's been hearing something there...

What I've realized now is: maybe she interrupted a regeneration process with it. That could also explain why it sounds a bit strange...

In the past, turbochargers have always been a sign of impending oil leaks for me. Is that always the case? Because currently, the intercooler pipes seem to be relatively clean...

I'll check the timing belt again. However, it was perfectly adjusted (and readjusted several times after the engine over-revved).
The whistling sounds like a turbocharger. Unfortunately, with this one, the entire axle needs to be removed to get the turbocharger out.

Thank you very much in advance!

All of our turbos in the TDI engines are whistling, with the exception of the AMF engine, where you don't hear anything; instead, the three-cylinder engine seems to be noisier.

With the V6 TDI engine, in certain situations, you might even hear a rattling sound.

Rüdi wrote:

All of our turbos in the TDI models whistle, with the exception of the AMF, where you don't hear anything; instead, the 3-cylinder engine makes a louder ticking sound. In certain situations, the V6 TDI engine can even produce a rattling sound

.
The BRE would sometimes make a gobbling sound like a turkey under certain load conditions when the throttle was suddenly released.

The throttle valve closed too quickly, and the insufficient air mass flow caused a stall in the compressor.

Best regards, Rainer.

Thank you for the assessment and the helpful comments!

Then I feel a bit relieved at that point. But as often happens when you focus on something, you also start to hear all sorts of things...