I have the infamous whining as a result from what seems to be air in the power steering system. I see no obvious leak, although a few months back I noticed low fluid so I topped it off and the cavitation stopped. It is back now, and when I check the reservoir it looks awfully frothy. As I said, I see no obvious leak. I tried bleeding the system as described in this post:
https://www.audiforums.com/forum/sho...ing+cavitation

No luck. Is there any way to %100 diagnose the pump versus air leak in a hose? Obviously replacing the pump is not ideal due to the cost and the pain in the rear it will pose.

If I have to replace the pump, is there anything tricky about this, i.e. any good advice from the experts out there?

 

OK, I have a hose question. I was looking over the parts website for power steering and it shows 3 hoses: a high pressure hose, a return hose, and a suction hose... What is up with that? My ignorant thinking is that the "suction hose" would be a likely culprit for bringing air into the system?

Can someone give me an anatomy lesson on the A6 power steering system? PLEASE?

 

I have the same problem with my 2002 3.0 A6. About a year ago they replaced some hose in the system and it fixed the problem. Now any time the temp drops below 20 degrees the noise is ridiculous. It's really embarrassing how loud the noise is. Am I doing any damage to the car while driving like this? My P/S fluid level is fine. I just get a layer of froth in the reservoir. Any suggestions?

 

The weird thing is, now the cavitation has subsided. According to the repair manual turning the vehicle wheels from end to end, pausing for a second at each stop point will build the maximum pressure in the system. Doing this several time with the cap off the reservoir may work out the air in the system. Once the weather warms up I plan on doing a complete system flush and fill, along with many other fluids (its just about time for my 80K service). I have no idea where the air is getting in from, but according to the repair manual diagram there seems to be numerous places where air could sneak in. There are a tremendous amount of connections along the way to/from the reservoir...

 

I've had this noise the past two weeks and was going to bring it up when I bring it in for the 45k service. I'll check the fluids to see if it will correct the noise which makes my A6 sound very ill. I also hope the weather warms up but thats not in the forecast.