Location: Far western Kentucky (transplanted from central PA)
What kind of noise? Most power steering units will make noise when turning the steering wheel at a standstill which, by the way, is a BAD practice. It's best to avoid turning the wheels at a standstill and , if possible, wait until you have some forward or backward motion (sideways doesn't help...).
So how do you know if your powering steering is going out?
I too am interested in this question. I've had to add about 4oz of fluid twice over the past year. Yesterday when I was leaving work there was a zinging noise as I was turning left. Although, it decreased when I slowed down? After that, I could not get it to happen again but there was a little vibration in the steering wheel. When I got home the power steering fluid was low. I topped it off but haven't heard the noise since. I'll have to wait and see what happens after it sits all day and I leave from work again.
The pumps I've had go bad always make a groaning type noise similar to a low fluid sound. This noise is amplified in a turn. One went bad due to bearings in it going out. This again seemed to make a roaring/groaning noise. I've never had one make the steering system wobbly. Always just harder to steer due to lack of or reduced hydraulic assistance of the pump.
Of the two Toyota pumps that died on me, both were due to the front seal (where the shaft of the pump comes out and attaches to the drive pully) failing. Couldn't keep fluid in them. Don't make the mistake I did and buy the toyota pump seal kit thinking you'll just put a new seal in. The kit was expensive and once apart I found the shaft of the pump rusted. I couldn't get it smooth enough to seal again.... so I had to buy a new pump anyway!
Whining noise when turning and even when straight forward at RPM's 1000 to 1200 RPM. I don't know what it is. It's most likely the pump but I'm also thinking that it could be the rack and pinion. it seems like there is constant hydraulic flow noise happening and the rotary valve that opens up the flow is in the rack and pinion.