2006 Grand Caravan. Power steering pump whines at air temperatures below 85 degrees. Dealer has relaced pump and belt twice in the last two years but whine recurs as weather cools. Is there something we have missed?
I had same issue a week ago I replaced my pump multiple times as well.
Depending on miles / age of car you may want to try this:
You should have a remote PS resevoir on top center of engine. In this resevoir is a filter that is most likely clogged and the noise you here is the pump cavitating from not getting enough fluid flow. A simple fix is to drain fluid, I removed lower hose from resevoir and put end in bottle. (make sure to put a rag under this area as some fluid drips during this process) You must plug nipple on resevoir with finger quickly after detaching. I had a helper start engine for a few seconds, this flushed my fluid quickly into plastic bottle, or just let nipple drain into a little pan.
Look down thru the fill cap hole and you will see filter. I could not figure a way to get filter out so I popped a couple holes in filter using a screwdriver. This solved the flow issue. I replaced fluid w/ new ATF+4 transmission fluid per mfg. recommendations. If you are concerned about lack of filter you could order a new resevoir from dealer and install. It seemed quite teadious to get this resevoir off the engine and considering the miles on my vehicle I decided not to replace and let it go and run it with a hole in filter. It is a sealed system w/ no real entry point for dirt anyways.
Actually there is no reason to drain fluid to test this you could just poke screwdriver in cap hole, but I wanted to see what I was doing.
Or better yet, tell dealer of this theory and have them replace resevoir for you under warranty !! 
To skraw910, you stated “I replaced fluid w/new ATF+4 transmission fluid per mfg recommendaions.” Did you really put transmission fluid into your power steering pump? Was this why the filter was clogged and you changed the pump multiple times?
MANY PS systems use ATF…For many years, that was the standard PS fluid…I suspect most “special” power steering fluid is just re-packaged ATF…
Most packaged PS fluid is ATF minus the dye and essential additives …aka hydraulic fluid.
You can put a Magnefine on the return line. It’s available from any NAPA. It will assure that any debris is caught. It has an internal bypass and should last for years.
Wix will have the ATP version of this, but you can use the part #
http://www.wixconnect.com/images/filters/4787_1.gif
I would suggest using Auto-Rx for this unit. You will already know how to exchange the fluid after a few hundred miles. www.auto-rx.com