Steering squeal or hum

Hello fellow DIY enthusiasts,

My Audi A4 2.0 TDI quattro, manufactured in 2007 (see Autoscan), makes strange noises when steering.
It's like a humming or squeaking sound; I don't know how else to describe it.
"This squealing noise only occurs when starting the car and turning the steering wheel at the same time, and it only happens around 1000-1500 RPM; after that, it disappears. There's no noise to be heard while driving normally."
The oil level is okay, and there's no sign of oil consumption. When I bought the car with 5000 km on it, the oil level was at the minimum, and since then, there has been no change in the oil level.
I can't pinpoint the source of the problem; it could be coming from the power steering pump, the steering rack itself, or the belt.

The error memory was empty, as expected.

Has anyone else experienced sounds like that?
What can I check before replacing parts based solely on suspicion?

You're welcome.

Sure, here's the translation:

"SG" can have different meanings depending on the context. It could stand for "Spielgemeinschaft," which is a German term for a sports club or association that combines players from multiple teams or organizations. Alternatively, it could refer to "Säkularkantor," a type of church musician who does not hold religious beliefs. Finally, "SG" might be an abbreviation for "Sonstige," meaning "other" or "miscellaneous."

Quote:

These squealing noises only occur when starting and steering simultaneously, and this only happens at approximately 1000-1500 RPM; then it's quiet again. There are no noises to be heard while driving either.

Buzzing or squealing – unfortunately, there's a big difference. A more detailed description would be helpful.

Cause of squealing: Insufficient or worn serpentine belt tension, defective generator clutch (resulting in an unstable drive system).

Cause of humming noise: Power steering pump is drawing air, fluid level is too low.

If I understand correctly, the fluid level is still at the minimum mark. If that's the case, fill it up to approximately the maximum mark using the appropriate hydraulic oil for the central hydraulics.

I have rarely encountered a squeaking ball joint (tie rod end). However, this issue should be reproducible even without the engine running.

Hello,

Thank you for your reply; it's more of a buzzing sound when I need to concentrate.
The fluid level is currently at the maximum mark; it was once at the minimum mark, but since then, it has been checked with each refueling.
I checked all the lines that obviously belong to the steering system and found no leaks.
Does the pump draw air directly from the container?

Sure, here's the translation:

"SG" can have different meanings depending on the context. It could stand for "Spielgemeinschaft," which is a German term for a sports club or association that combines players from multiple teams or organizations. Alternatively, it could refer to "Säkularkantor," a type of church musician who does not hold religious beliefs. Finally, "SG" might be an abbreviation for "Sonstige," meaning "other" or "miscellaneous."

Quote:

Do you mean the pump is drawing air directly from the container?

First, you would need to determine whether the noise is actually coming from the power steering pump.

I wasn't sure if you had adjusted the fluid level, or if you just found it to be acceptable at the minimum mark. Also, did you use the correct type of fluid? When bleeding the system, there should be bubbles coming from the reservoir.

You need to try and narrow down the source of the noise as much as possible.

Hello,

Thank you for your reply. There is no foam visible.
The original oil has been filled in.
I'll try to pinpoint the source of the noise when I have someone else with me.

Sure, here's the translation:

"SG" can have different meanings depending on the context. It could stand for "Spielgemeinschaft," which is a German term for a sports club or association that combines players from multiple teams or organizations. Alternatively, it could refer to "Säkularkantor," a type of church musician who does not hold religious beliefs. Finally, "SG" might be an abbreviation for "Sonstige," meaning "other" or "miscellaneous."

Hello everyone,

The sound is more noticeable inside the vehicle than outside (in the engine compartment).
I suspect the PK6 belt is the problem because it looks worn out.
Ich werde diesen bei nächster Gelegenheit abnehmen und erneuern (incl. Tension spring (or tensioner).
Then I'll also try turning the pump manually to see if anything seems unusual.

Does anyone have any other ideas or comments?

Sure, here's the translation:

"SG" can have different meanings depending on the context. It could stand for "Spielgemeinschaft," which is a German term for a sports club or association that combines players from multiple teams or organizations. Alternatively, it could refer to "Säkularkantor," a type of church musician who does not hold religious beliefs. Finally, "SG" might be an abbreviation for "Sonstige," meaning "other" or "miscellaneous."

Quote:

Then, if I have the opportunity, I will also try turning the pump manually, perhaps something noticeable will happen.

Don't forget to check out the Lima free run while you're there.

Hello,

The belt drive is disassembled, and everything on the tensioner pulley and idler pulley is tight and shows no signs of wear or issues.
The power steering pump has some slight radial play.
The free-running clutch of the transmission is making some noises.

I will either buy a new outdoor enclosure tomorrow or compare it to the old one.
Would you also replace the tensioner pulley/guide pulley at the same time?
What would your diagnosis be?

Sure, here's the translation:

"SG" can have different meanings depending on the context. It could stand for "Spielgemeinschaft," which is a German term for a sports club or association that combines players from multiple teams or organizations. Alternatively, it could refer to "Säkularkantor," a type of church musician who does not hold religious beliefs. Finally, "SG" might be an abbreviation for "Sonstige," meaning "other" or "miscellaneous."

[Translating...]

Mit dem Freilauf wäre ich vorsichtig.

Guck mal hier: https://community.dieselschrauber.org/en/viewtopic.php?t=26419&highlight=freilauf

Hello,

Thank you for the link.
"So, I removed the generator, including the freewheel mechanism, because I don't have the right tool for removing the freewheel."
What I forgot to mention is that I heard the noise most clearly when I experienced "engine speed fluctuations" in the range of 1000 to 1200 RPM.
Therefore, I opted for the "free run" option.
The free-running clutch looks okay externally in terms of rust or similar issues.
Under the cover, the freewheel is oily, which leads me to believe that the freewheel is the source of the noise.

@Autoservice
What would be your choice?

Sure, here's the translation:

"SG" can have different meanings depending on the context. It could stand for "Spielgemeinschaft," which is a German term for a sports club or association that combines players from multiple teams or organizations. Alternatively, it could refer to "Säkularkantor," a type of church musician who does not hold religious beliefs. Finally, "SG" might be an abbreviation for "Sonstige," meaning "other" or "miscellaneous."

If the clutch disc is already on the table and you have a new clutch ready, I would replace it even if the old one still seems intact.

Hello,

I've now replaced the tensioner and the freewheel.
So far, I haven't heard anything more, but if that changes, I will post it here.

Thank you for your help.

Sure, here's the translation:

"SG" can have different meanings depending on the context. It could stand for "Spielgemeinschaft," which is a German term for a sports club or association that combines players from multiple teams or organizations. Alternatively, it could refer to "Säkularkantor," a type of church musician who does not hold religious beliefs. Finally, "SG" might be an abbreviation for "Sonstige," meaning "other" or "miscellaneous."

Hello everyone,

Unfortunately, the noise is still present. The noise is similar to the sound you hear when reaching the maximum steering angle.
Therefore, I suspect the problem is with the steering system (power steering unit) because the noise occurs even while driving. My guess is that it might be a pressure relief valve in the power steering system.
The oil level in the power steering system is unchanged, and there are no visible air bubbles (no foaming).
The sound gets louder as it gets warmer.
Does anyone here know of this problem/solution, or is it simply considered "normal" or "state-of-the-art"?

Sure, here's the translation:

"SG" can have different meanings depending on the context. It could stand for "Spielgemeinschaft," which is a German term for a sports club or association that combines players from multiple teams or organizations. Alternatively, it could refer to "Säkularkantor," a type of church musician who does not hold religious beliefs. Finally, "SG" might be an abbreviation for "Sonstige," meaning "other" or "miscellaneous."

The buzzing sound, as "Autoservice" already mentioned, is likely caused by air entering somewhere between the power steering fluid reservoir and the pump.
The hose doesn't need to be oil-tight because oil is thicker than air!
"I had a similar issue with a Passat 35i; in that case, the problem was a hose."

Hello,

If there's air in the system, shouldn't you see foam in the expansion tank? Or am I wrong?
I'm going to take a closer look at the hoses; maybe I'll see something.

Sure, here's the translation:

"SG" can have different meanings depending on the context. It could stand for "Spielgemeinschaft," which is a German term for a sports club or association that combines players from multiple teams or organizations. Alternatively, it could refer to "Säkularkantor," a type of church musician who does not hold religious beliefs. Finally, "SG" might be an abbreviation for "Sonstige," meaning "other" or "miscellaneous."

You can also upload WAV or MP3 files here in the posts.

From my own experience, I can say that a worn serpentine belt can also produce interesting noises, even if it looks okay at first glance.

I haven't found anything in the previous posts that indicates the belt has been replaced.

Best regards, Rainer.