AVF Motor Noise: Flow Sounds Up to 2000 RPM

Hello everyone,

I've been a reader for quite some time, and today I also have something to say .
I've had a Passat 3BG, manufactured in 02/2004, with 80,000 km on the clock, equipped with a TDI PD AVF engine (transmission: AG5, Tiptronic), and I'm very happy with it.
The car is running well, but I've noticed that there are strong air flow noises (likely on the pressure side after the turbocharger) that occur at increasing load, roughly between 2000-2300 RPM. It's not excessively loud, but it's noticeable.
Today, I compared it to another AVF (Active Vibration Filter) in an A4, and there was nothing to hear.

It can be described as a 'puffing' or a very loud 'slurping' sound. It's not the normal whistling sound you hear at partial load, it's different. It also has a kind of grinding noise.

Could this be related to leaks in the charge air system that the turbocharger is still able to compensate for?
VAG Com shows good pressure readings, up to almost 2500 mBar of absolute pressure .


And another question:
Is there anywhere a sensor or module for measuring oil temperature or oil pressure?

Thank you in advance.

corryfan wrote:

that up to approximately 2000-2300 RPM, strong air flow noises (likely on the pressure side, near the turbocharger) occur with increasing load. One could describe it as "blowing" or vigorous "slurping." Could this be related to leaks in the charge air system that the turbocharger can still compensate for?

Yes, that is quite possible.

I would like to investigate the issue (look for oil leaks, check the pipes, etc.) before the loader potentially fails due to constant overload.

What should one pay particular attention to when dealing with arteriovenous fistulas (AVFs), and are there any specific considerations?
I will write again as soon as there is any news.

Okay, I've been looking into the engine issue a bit (I've only driven carbureted engines before). There was some oil in the intercooler hose, but it was just a thin film. That should be normal. All the hoses that are accessible from the top seem to be okay.
Everything else is up to VW to check; let's see what they find.

Could it be that the AVF (presumably a piece of software or hardware) is no longer processing engine oil temperature data? There is also no value for it in the label file.
Same question about:

- LLK temperatures before/after LLK.
- Exhaust temperature sensor (turbo)


I can't find any values there. Is it really not available?

corryfan wrote:

There was oil in the charge air duct, but it was only a thin film.

This should be normal.
Yes, that's normal. What's concerning is the oil leak on the outside of the pipes/coolant lines -> see articles about common mistakes.

Quote:

Could it be that the AVF is no longer processing the engine oil temperature data? There is also no value for it in the label file. Same question about: - LLK temperatures before/after LLK. - Exhaust temperature turbo

I'm not familiar with oil temperature processing in the MSG. The AI system analyzes this data in conjunction with the calculation of the water-in-oil (WIV) content.

For the Low-Temperature Liquid Cooling (LLT) system after the Low-Level Cooling (LLK) phase, there is a readable diagnostic value in the Main Water Box (MWB) 7. This value approaches the outside temperature during extended operating phases and is highest in the maximum power (Pmax) range.
There are no temperature sensors (in standard production cars) before the LLK (radiator) and before the turbine.

Okay, so, today I went to the and drove around the area with the master.

Result:
The noise from the airflow (which can be heard from LL up to approximately 2500 RPM) is 'normal' and tends to get louder with increasing mileage. What do you think about this? Is that even possible? Has anyone had experience with this on an AVF engine?
My comparison vehicle had 50,000 kilometers less (30,000 km instead of 80,000 km), perhaps that's also related.

In addition, the hose under the coolant reservoir is leaking (by the way, it's normal for all of them to leak, and there's nothing you can do about it. I'm almost speechless).
Please provide the image so I can translate the text.

'Is there a way to determine if the charger has been damaged by the leak over the past few kilometers, or if there's something wrong with the charger itself? The car is running 'normally' well, so from a driving perspective, I would say everything seems to be okay.'

I still have 3 months of warranty on this new product, after which it will expire.
Sure, no problem!

http://www.car-revolution.de/passat/IMG_0334_2.JPG

'The 'good' guy is right! I don't know of any automatic transmission fluid (ATF) cooler that doesn't leak at this point! It's not really a big deal. However, I didn't want to accept it because it was contaminating my foam blocks that protect the underside of the vehicle. The friendly mechanic couldn't fix it with new seals, which happens frequently. So, I sealed it myself. I obtained new seals and installed them using a special sealant. The sealant is resistant to oil, temperature (up to 300°C), and pressure, and it doesn't stick. This is important for disassembly. I've been driving with it for about half a year now, and the connections of the ATF cooler are completely dry!'
However, despite that: this seepage seems to be quite normal. It's happening precisely in that area where the hot oil vapor condenses back into liquid as it cools, and then collects at the lowest point. Those areas probably aren't as airtight as they should be, but they should be.

Greetings.

Hi,

"Try to figure out if it's just a slight oil leak at that spot, or if there's a significant air leak. The former is not critical, the latter is. At the very beginning, I had a hole in almost the exact same spot... that was noticeable because of the noises it made. But in that case, it was leaking so much air that you could feel it even when the engine was idling."

Okay... remove the disguise, put your hand in front, and have someone give it some gas while it's idling. Even if it's claimed that you won't notice anything... in my case, a very noticeable blast of air came out.

Have it sealed and you're done (or do it yourself).

Due to my lack of knowledge at the time, excessive reliance on the dealership's advice, and despite having a forum for support, I drove the brand new car for almost 5,000 km like that (well, back in early 2002). It didn't cause any damage, and now, with 65,000 km on the odometer, the engine and turbo are still running perfectly.

Best regards,

Jan.

Sure, here's the translation:

'Quick question:'

However, does the LLK accumulate oil sludge over time, or does it not?

Hi Mady, it's me .

Bzgl. LLK:
'No, I don't believe that, because the system only contains pure engine oil, and only in minimal amounts. At least, that was the case for me when I sealed it. There was absolutely no 'dirt' or sludge present.'

Regards,
Mike.

Jan6K wrote:

So... remove the disguise, put your hand in front, and let someone give it gas while it's idling. Even if it's claimed that you won't notice anything... in my case, a clearly noticeable jet of air came out.

Hi Jan,

"Non-elastic" holes can be reliably identified in this way.

You can, without any assistance, use VAGCOM to access the basic settings of control module 11 and hope that the idle speed (at approximately 1400 rpm) is increased. If the boost pressure reaches 100 mbar or more, and this happens repeatedly within a 10-second interval, it will whistle quite loudly from all the openings.
Does the idle speed remain at 900 rpm? If so, you're just as smart as you are in normal operation.

Cracks, etc., that only open at a higher pressure cannot be detected in this way, but only by analyzing the oil or by pressing the lower liner (LL) section.

Quote:

However, LLK does not accumulate sludge over time, or does it perhaps do so

?
The sludge isn't just made of oil, but also contains a high proportion of debris and particles. Where would these particles come from if not from behind the air filter?

Without an assistant, you can use VAGCOM to access the basic settings of control module 11 and hope that the idle speed (which should be around 1400 rpm) is increased.




Hi,

I've already done quite a bit with VAGCOM, but somehow I'm stuck right now. Measurement block and basic setting?? Can you please explain it to me ?
On Friday, I will be at the , replacing the O-ring. I will test beforehand to see if it was 'leaky'.

corryfan wrote:

I've already done quite a bit with VAGCOM, but somehow I'm stuck right now. Measurement blocks and basic settings??

If you don't know what a measurement data block is, what have you been doing with VAGCOM?
-> Dial 011 and select "Basic Settings".

See also https://community.dieselschrauber.org/en/viewtopic.php?t=10810.

Regarding VAGCOM: It seems it's not available in the shareware version, which is why I'm not familiar with it. I'll take a look at the full version.

Regarding the hose:
I received 2 new seals today (by the way, there are 2 part numbers, one of which has been replaced. Probably an optimized part?).
Unfortunately, we didn't check the air tightness because we were under time pressure and the mechanic assisting us wasn't very cooperative (they tend to be dismissive, saying things like 'they're all leaky anyway').

My engine noise is still present, and it's clearly coming from the area around the turbocharger, which is located in the front on the right side.
It seems like the engine is running better now; I'll test it thoroughly tomorrow (with two trips of 450 km each).

Hello!

Bis gestern habe ich auch noch gedacht das das Rausch normal währe. I have that too.
I slid it onto the hose connector, which is arranged slightly differently on my A6 but looks the same.

When I bought my car (A6 1.9 AVF), I immediately replaced the leaky connections with new ones.
now fitted with new green seals (the old ones were black and crushed due to incorrect installation).

Yesterday, while working on my car for a different reason, I noticed that the hose connections at the bottom were smeared with oil again.

I think I've found the cause. My connection is now down for a distance of 200 km.
The clamp that secures the pipe engages behind two protrusions on the connecting pipe.

My suspicion is that the nozzles are wearing away due to abrasion caused by vibrations.
So that the hose can be pushed slightly out of the coupling using the boost pressure.
(unless it was designed that way from the beginning / I have no idea, I bought the car like this).
Upon closer inspection, the insertion tube is centered within the socket of the mating part by small protrusions located at the end of the cylindrical section of the insertion tube. When pushed out, these protrusions rest on the edge of the socket and gradually work their way in. Eventually, the socket slips off the protrusions, or the protrusions become so embedded that the insertion tube is no longer centered.
Bending moments (from the rest of the pipe) and gravitational forces are now acting on the seal. Due to these stresses, the seal flattens at one point, creating a free cross-section on the opposite side of the pipe.

leaky connection.

I used TIG welding to add some material behind the locating pins and then used a file to create a new contour.

My connection is now sealed, but that wasn't the cause of the problem.
The noise was coming from my engine. In my case, the pressure hose between the turbocharger and the intercooler, on the side, had cracked. The oil was spraying into the wheel well in such an unfortunate way that you couldn't see it from above, and only with a flashlight from below.

best regards

wvg

hi
Thank you for the great contribution. I'll double-check everything and let you know.
By the way, I also had the black seals installed (my car was manufactured in February 2004), and now there are two green seals installed.

The vehicle is running just as well as before, there seems to be no difference.

@ulf: Is it possible to increase the RPM setting in the 'default' configuration? What exactly happens when that's done?

'It doesn't quite fit the topic, but does anyone know what 'status 2 or 4 or 6' means for the PD (piezo injector) elements? I logged about 300kB of data on Saturday (two 450km highway trips), and this issue occurred occasionally.'

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

'Hello'
Sebastian.