Air Bubble RS TDI BMN - Not Localizable

Hello everyone,
I'm currently experiencing the following problem with my 2007 Octavia RS TDI, engine code: BMN.
"For a while now, he's been making a whistling sound somewhere whenever I demand power. It sounds like a turbocharger air leak. However, the pressure readings were within the normal range when checked with VCDS. Last weekend, I removed the pressure line from the turbocharger to the intercooler and tightened two hose clamps, one of which was slightly loose."

After dismantling and a test drive: everything was fine, no more issues. But 100 km later, the problem reappeared.

Today, I pressure-tested the intercooler piping leading to the turbo, according to the repair manual, using 0.5 bar, and I didn't hear anything. It seems everything is sealed properly.

Does anyone have a tip for me about what else I could test? I have absolutely no idea anymore .
Is it still possible to check the exhaust system of newer cars using the "rag-and-exhaust-pipe" method?

Thank you in advance.

Daniel.

Quote:

After dismantling and a test drive: everything was quiet, no more leaks.

100 kilometers later, it was back again.

Quote:

Apparently, you've been looking in the right place.

Today, I checked the intercooler piping from the turbo according to the repair manual, using 0.5 bar, and I didn't hear anything. It seems everything is tight.

Does anyone have a tip for me about what else I could test? }

Increase the pressure (to 1 bar) and, if possible, wiggle the hose connection.

Okay, I applied more pressure and fiddled with everything possible... Nothing. I also immediately removed the AGR valve and the shut-off valve and checked to see if anything was not sealing properly, but everything seems to be okay there as well.
The next candidate would be the DPF (Diesel Particulate Filter), or perhaps the gasket and clamp associated with it. This could also explain the abnormal turbo noise I'm hearing, even though the VTG (Variable Turbine Geometry) seems to be working smoothly.
Can you still block the exhaust path, for example at the DPF, to locate leaks, or will something immediately break?
I just want to know why he was quiet after the last action .


Best regards,
Daniel.

First, consider whether it's an air noise (hissing) or a turbine whine.

Does the BMN also have the GT1749VC?

My dog whimpers a little bit when it's cold (in the mornings during the winter, but not in the summer).
It's so quiet that I'm sure no one else can hear it.

In the summer, when you drive with the windows open, you can clearly hear the sound of the air flowing.
It doesn't sound like it's leaking.

It's only interesting because it seems to be related to the fact that it only happens when driving with the top down in the summer, and then this "turbo sound" suddenly appears – especially in town, when going uphill, where there's boost pressure and reflections off building facades.

m;

The whistling started much earlier, while the turbo whine came later. I was 100% sure it was a leak in the charge air system, but when I checked, everything was quiet except for a slight hissing sound coming from the engine head, which is normal. That's why a pressure test couldn't be performed.
The whistling sound only occurs when maximum power is demanded. In 5th gear at 60 km/h with full throttle, it starts.
I've gotten used to the howling noise; there are a few VAG cars around here that make the same sound.
According to the workshop, it's supposedly not dangerous, but in my opinion, that's clearly a mistake.

I was also thinking about kidney disease or something similar, but I don't know the symptoms. You can see, everything seems suspicious right now.
Best regards,
Daniel.

I recently replaced several hose clamps on the intercooler hoses and installed a new air filter. However, there has been no change in the noises; the whistling and howling sounds are still present.
Today, while on the train, a new symptom appeared. At least, I hadn't noticed it before.
Coming from 6th gear at full throttle, 220 km/h, I engaged the afterburner. In afterburner mode, there's a wave-like behavior. It's not severe, but noticeable. The tachometer confirms this.
So, every second, the speed decreases, it lingers there for a moment, and then decreases again in the next second.

In a "boost" mode, it's unlikely that such behavior could be caused by anything else, right?
Which other measured values would be interesting to check besides engine speed, boost pressure, and mass airflow?
The MFA (Multifunction Display) shows a fuel consumption of 0.0L when running, which is as expected...

Best regards and have a nice weekend.
Daniel.

It didn't start up properly again after work today; it had to crank for a while, and it was making a strange noise.
At the beginning of the log, the car is idling, then some city driving, and towards the end, a brief period of full throttle on the highway.
On Thursday, I'm having my buddy check the tandem pump.

@dieselmartin: The noise has been there for a while now, and it's definitely not normal. The windows are closed; when I open the window, it sounds even worse. It's like my wife is sitting next to me with a hairdryer.

Can someone take a look at this?

Best regards,
Daniel.

Quote:

Coming from 6th gear at full throttle with a speed of 220 km/h, I engaged the afterburner. In afterburner mode, there's a wave-like behavior. It's not strong, but noticeable. The tachometer confirms this. So, every second the speed decreases, it stays at that level for a short time, and then decreases again in the next second.

In "coasting" mode (foot completely off the accelerator), there is essentially no power being delivered. The vehicle must continuously decelerate.
If not, usable fuel must come from somewhere.
And if it's not coming from the nozzles, it could be engine oil leaking onto the timing chain.

Unfortunately, it is very difficult to correctly interpret a recorded or reproduced sound.
The noise may be normal, but it doesn't necessarily have to be.

Based on this and your description of the problem, I would advise you to have the vehicle inspected by a qualified workshop or to get a professional opinion before any further damage occurs.

Okay, thanks for the effort!
I'll talk to my boyfriend on Thursday about what we still want to do. He works at a company that's part of the VAG group.
It's very frustrating, but I would bet that if one of the experts here in the forum had the car for a day, the problem would be found.

Best regards,
Daniel.

The tandem pump has been checked and is working fine, as is the internal seal. Today, I used my endoscope to inspect the exhaust manifold and was a bit surprised. But take a look for yourselves. The quality isn't great, but it seems it's probably sufficient.

Hi stummel, yes, we all thought the same thing. Even when he was on stage, it looked like there was a tear in his head. Especially since everything around it seemed dry. However, after cleaning the area, nothing more appeared.
I have to say: Unfortunately. Because that would finally be an explanation for my problems with the BMN.
The turbo is driving me crazy with all the noise, and I'm also having starting problems and performance issues every 1000 km. But there are no error codes, and the values I see in VCDS (in my opinion) don't seem unusual.
The only thing we found while changing the valve cover gasket was a completely loose valve cover. After tightening it, the engine ran more smoothly, and the starting problems were also resolved. And so it has been to this day, even after 1400 km.
No matter what is done, it only lasts for a short time...
New catalytic converter, new diesel filter, turbo hoses and seals, valve cover gasket, new intake manifold, new intake hose, air filter.
The tandem pump has been pressure tested: Everything is sealed internally, and the delivery pressure is correct.

I'll probably get under there again sometime soon, but honestly, I'm almost indifferent to it now, which is a shame because I actually like the car.

The only consolation is that my friend is having even less luck with his new E-Class. He had an engine failure at 20,000 km. And now it's his second new Mercedes with an engine failure.


Best regards,
Daniel.

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In coasting mode (foot completely off the accelerator), there is essentially zero fuel injection. The vehicle must continuously decelerate. If not, then usable fuel must come from somewhere.

It depends on the definition of "continuous".

Yes, he has to postpone.
NO, even without fuel and WITH ERRORS, it can still be wave-like.
Specifically, that's exactly when someone is tampering with the VTG.
It's also used for braking. And if it's now drawn in a wavy pattern, the tractor will also brake in a wavy pattern.

I don't know how significant this is, whether it's noticeable, or how to see it in the Siemens MWB.

You can see it clearly at ASV.

m;

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It depends on the definition of "continuous". Yes, he has to postpone. NO, even without fuel and WITH ERRORS, it can still be wave-like. Specifically, that's exactly when someone is tampering with the VTG. It is also used for braking. And if it is now drawn in a wavy shape, the tractor also brakes in a wavy shape.

It might work at low speeds, but not at:

Quote:

I was traveling at 220 km/h in the 6th gear when I engaged the overdrive. In overdrive, there is a wave-like behavior. It's not strong, but noticeable. The tachometer confirms this. So, every second the speed decreases, it stays at that level for a short time, and then decreases again in the next second.

I can't imagine that.

Today, I tried installing a new N75 valve (or pressure sensor) as a test, but there was no change (of course).
I performed the swap because I experienced the infamous "foghorn" or "mooing" sound today after starting the engine. It was faint but audible.
Could you please tell me again exactly which machine parameters (MWB) I should log? And whether I need to log full load or partial load data in order to make progress with this. I really think that without the forum, it won't run 100% anymore.
I already have a knot in my stomach, and now I find myself thinking the worst about every new sound I hear.
If someone then looks at the logs and says, "Replace the turbocharger, and it will work again," then I will do that. But right now, it's really like searching for a needle in a haystack...


Best regards,
Daniel.

Okay, just before the night shift on the train, the MWB 3.8,11 was running at full load, once in fourth gear and once in fifth gear. It would be very helpful if someone with expertise could take a look and share their opinion.

Thank you in advance.
Daniel.