Mine does the same but only when I turn on my ac ( extra load on the belt) I figure its an idlers puppy gone bad or something.. mine was just like yours and I replaced my belt and tightend it up a bit so now it only happens with Extra load while its cool.. that or it could be your power steering pump. Low fluid / leak will make them sqeal like a pig from help. Check ur level and if there is an fluid on/ around the pump and hoses