I have a friend with a 2000 Alero 3.4. She said that it makes a groaning sound when turning. I went out to the car and duplicated the sound when turning the wheel. I checked the reservoir with the engine running and there was little fluid and what fluid was there was frothy. I put the cap on the reservoir and turned off the engine. This is were it gets weird. I opened the reservoir cap and I heard a rush of air and the fluid was almost to its normal level (still bubbly however). Does this sound like a blockage issue or is the pump cavitating and compressing the air? I also noticed a leak under the car and it seems to be power steering fluid. What type of fluid do these cars use for PS? Thanks for any help.

 

I would say cavitation. For fluid, any fluid that says it meets GM specs is okay. You can find the GM part number for the fluid in the back of the owners manual if you want the factory fluid, but they are all about the same.
My Alero did the same thing, and by sucking the reservior dry and refilling with new fluid, driving a few days, then sucking it dry again, refilling about 5 times, the sound went away. I figure I got about 80% of the old fluid out by doing that. There is no change schedule for fluid, but it does need it after 5 years or so I think. Before you do all that, you need to clean the area where you suspect a leak, and monitor it.