MartinBDK

Hi

I have recently been blessed with a new sound in my 08 S8. It usually starts when I drive the car a little bit harder that normal, and it seems to be coming from somewhere behind the steering wheel (or perhaps just from "the engine area").

Normally it is a whining, or a high pitch humming of some sort, and et even vibrates in the steering wheel. It feels like a super fast vibration, and it is primarily noticable when the engine is idling. When i rev up, it changes pitch.

At one point it was like I could provoke it by turning the wheel, so that when the wheel reached certain degrees, the humming was much more pronounced.

I have tried to record it, but it is hard to capture on film. I will try again when it is at its worst.. Any ideas?

MP4.2+6.0

The obvious would be the power steering pump. Not fun on an S8 IIRC--the Rube Goldberg gear drive found on FSI motors in general. As you listen for it, think about whether it is temperature related. When my A6 4.2 pump got tired over the years, I noticed in very cold weather (snow on ground stuff) that pump noise was a lot more noticeable, especially around start up like when warming car to thaw glass and such off. You correlated it to engine speed, so logically it will be something like PS pump--or A/C, water pump or alternator as other scenarios. Save for that correlation to engine speed, I might actually have guessed the suspension compressor. I had noticed some noise like part of what you describe when the suspension compressor cycled more when a front strut leaked on way to replacing it. See if you notice any connection with when raise lower lights are on to check that one off. You can also switch AC to the Econ mode to see if that has any effect.

Separately you might also look at your engine mounts. Especially look at the torque mount as one a variety of us w/ various motors have had to deal with. If those have issues, you may well feel more vibrations that can seem like they come though steering wheel and such.

MartinBDK

Im not entirely sure if it is directly related to engine speed, it could just be the engine drowning out the "funny" sound.. I will start with the easy test: turn of A/C via eco mode, and try to put the suspension in high mode and back into comfort to see if that changes the sound.

In regards to the engine mounts, wouldn't the vibrations be "slow"? Like when you drive on cobble stones or a particular bumpy road? This feels more like holding an electric toothbrush

MP4.2+6.0

On the mounts, while what you are thinking is reasonable, if a mount fails then it loses the hydraulic oil buffering that is built into all Audi mounts these days. The torque mount can also just split in two. If either the oil is gone or it is split but the two sides touch, lots of vibrations you might not notice come right through. No different than many a motor or other things mounted on rubber components where if one of those fails, lots of vibration, noise etc. get transmitted through. Theory aside, i had failed torque mounts in both my 2000 A6 4.2 and my 2006 A8 W12. In both cases, you could perceive more vibration at times. Sometimes clunks in the drivetrain too, especially full throttle shifts. A failed torque mount not attended to can lead to accelerated wear on main mounts as well, which all add up. Plus, the mains are pricier.

MartinBDK

Thanks for scaring me

I have a strong feeling that it might be something with the steering, because of the time where it only presented itself when the steering wheel was in a few precise positions (if that makes sense).. I will try the A/C / suspension thing next time i go for a drive though..

nicky_1

Hi there,
I've had the similar funny high pitch wining sound since I bought my A8 aswell. Mine is related with ambient lighting - when you go into your MMI menu and decrease the ambient lighting not only the lights go dimm but also the sound gets quieter aswell. It's like the led strips in doors have little fans cooling them or something. Might not be the case but that's what I found in mine.

MartinBDK

So I had the car brought to my local car wizard, and after diggin' his way down to the servo-motor, he found that there was only 75% of the intended servo-oil in the system. At the same time he couldn't find any leaks, so he just topped it up, and crossed his fingers. Now the strange sound has completely disappeared.. So thats good news. Now im just exited to see how long it lasts..

Sci-fi_Wasabi

Martin, So just to clarify, exactly what servo-motor are you talking about? Do you mean the power-steering pump oil? If it is anything unusual, can you take a pic of it and where to fill the oil on this?

MartinBDK

Sorry, yes the power steering pump-oil

The car is all back together, so I cant take a picture. It is a bit of a hassle to get to the fill-up-place i think?

Shark_V8

Actually I was going to say check level, because it sounded like you had cavitation - this occurs when air bubbles get in the system and through the pump

Not sure if Lucas additives are compatible, but Lucas is a quality product and smoothed out steering in some other cars I had (Audi V8 and Porsche 928)