[Alvos]

Typically, the power steering pump makes a whining noise (either because it's under heavy load/friction or because the fluid is simply too low). Squealing/whistling is a belt, but it never hurts to replace them anyways. Still, if there's water or condensation in your power steering system, it's been known to cause some odd noises in the past. My Ford Aerostar (don't ask...) had water mixed into the power steering fluid (murky, opaque color is typically a good indicator of this for most brands) and it sounded like a boiling tea kettle. Once I bled and refilled the system, it stopped.