Steering Noise: Causes and Solutions

Hello fellow DIY enthusiasts,

My Audi A4 2.0 TDI quattro, manufactured in 2007 (see Autoscan), is making strange noises when I steer.
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 at approximately 1000-1500 RPM; after that, it disappears. There's no noise to be heard while driving."
The oil level is okay, and there is no sign of oil consumption. When I bought the car with 5000 km on the odometer, the oil level was at the minimum, and there has been no change in the oil level since then.
I can't determine whether the problem originates from the power steering pump, the steering gear itself, or the belt.

The error memory was, as expected, empty.

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

Certainly. Here's the translation:

"Thank you very much."

SG.

Quote:

These squealing noises only occur when starting and turning simultaneously, and only at approximately 1000-1500 RPM, after which they disappear. There is nothing to hear while driving.

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, or a faulty generator clutch (resulting in an unstable belt drive).

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. If that's the case, fill it up to approximately the maximum level with the appropriate hydraulic oil.

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 humming sound when I need to exert myself.
The fluid level is currently at the maximum mark; it was once at the minimum mark, but since then, it has been checked every time it's refilled.
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?

SG.

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 level. Also, did you use the correct type of fluid? When bleeding the brakes, there should be bubbles coming from the reservoir.

You have to try to 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.
I'll try to pinpoint the source of the noise when I'm with someone else.

SG.

Hello everyone,

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

Does anyone have any other ideas or comments?

SG.

Quote:

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

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

Hello,

The belt drive is disassembled, and everything is tight and without any issues on the tensioner pulley and the idler pulley.
The power steering pump has some slight radial play.
The free-running clutch of the Lima makes slight noises.

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

SG.

I would be careful with the free-running feature.

Look at this: 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, because I don't have the right tool for 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?

SG.

If the clutch disc is already on the table and you already have a new clutch disc, 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 I will post an update here if that changes.

Thank you for your help.

SG.

Hello everyone,

Unfortunately, the noise is still present. The noise is similar to the sound you hear when the steering wheel reaches its maximum angle.
Therefore, I suspect the steering system (steering gear) because the noise occurs even while driving. My guess is that it might be a pressure relief valve in the 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 "normal" or "state of the art"?

SG.

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, and 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.

SG.

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.