Need help diagnosing power steering problem

I have a 2000 Buick Park Avenue Ultra in which the power steering works perfectly fine in the first 10 to 15 minutes of driving but on dry days, after
which time, it gets harder to turn the wheel at very slow speeds, especially when parking. It also gets a little whinier sounding when turning. Also, when it starts getting like this, I can sometimes get a sound like the wheel is scraping something when I make a right hand turn.
I took it to a place that specializes in power steering and the mechanic, who drove the car and heard this noise, thinks the power steering and the rack-and-pinion is ok. He took a little of the power steering fluid out and put in an additive. The power steering seemed to be working great and the wheel noise was gone but the weather has gotten mild and dry lately and now it's back again, after driving awhile, of course.
I've been doing some reading on google and I'm wondering if it could be the power steering speed control valve getting stuck. But if it is that, why would I get the noise from turning right, unless that is unrelated.
This time I'm going to take it to a GM dealer but it would be nice if I could find any info here, so they don't try and rip me off and say it needs new power steering...Assuming they would be the type to do this.
Thanks,
Jeff
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wear the belt pulley, esp. the idler pulley, in a one-sided pattern. I.e., they wear the outer side of the pulley surface much faster than the inner & produce a tapered outer belt circumference. The belt would have a tendence to ride toward this outer, lower side & perpetuate itself. If your car has lots of miles you may want to replace these worn pulleys AND the tensioner; if not, just the pulleys--that is assuming you do find this wear. Of course, a new QUALITY belt would be in order. Belt slippage can occur so subtly that one may not hear it. HTH, s
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Thanks for the info. The GM mechanic didn't think there was anything wrong with the belt and the steering would not act up for him when he drove it...Gotta love intermittent problems!
It's not a huge problem at the moment so I'm just going to get the PS fluid flushed and replaced and if that doesn't help, I'll keep driving it until it gets more annoying or frequent. I mentioned that the last mechanic took some of the fluid out and put in an additive. This actually has helped more than I previously thought. Before this, the PS could get really hard to turn when parking and since then it hasn't been nearly that bad, so maybe there is something with the fluid, who knows. It would be nice if it's something that simple but I have a feeling it still won't be 100% after getting it replaced.
Jeff
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sounds like your fluid has lost it's viscosity & is now just spurting past the gear in the pump not developing much pressure, & making that noise. i'm going out on a limb with that because you said after the additive, it seemed much better. i'm guessing now that the additive has also been shot now. i would definitely try the flush & refill (make sure after you drain/fill it, you only run it for a short time after the initial fill, then shut off right away, as the fluid will foam & can damage the pump if you run it while it keeps foaming like that). remember, if you want to get the majority of the fluid out, you'll need to drain, fill, run, drain, fill, run, fill, run, check level.
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flush the system
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Sorry I should have followed up. I had it flushed and all is good now. I took it to a GM dealer and they checked out the PS and rack and said it was fine and the PS change has fixed it.
The seldom heard noise I get in dry weather, with the extreme right turn is another "problem". There is actually a service bulletin entitled "steering vibration/shudder/moan during parking maneuvers" for the 1997 to 2001 Park Avenue's. Installing a new power steering preasure (inlet) hose assembly will fix the problem. I'm not going to bother at this point since it's not that big of a deal. I'm not sure why I only hear it with right hand turns (going very slow or parking; on dry pavement) and not left. I suspect not all 97 to 2001 PA's are experiencing this problem or the owners aren't noticing it.
The actual link is below but I can't access it. My GM dealer did and gave me the print out. It also affects other Buicks as well.
http://service.gm.com/servlets/BlobShtml?ShtmlFilew7322&psdid 6&evc=sm
Jeff
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