When going 25 mph + and I turn the steering wheel there is a whispering noise coming from the engine compartment. This noise is not there when I turn the wheel when the car is stationary or moving fairly slowly. I particularly notice it on windy roads going 50 to 60 mph The power steering fluid level has not fallen and is correct. I have owned the vehicle for 3 years and had no steering issue before and not even topped up the steering fluid. The noise comes when the steering is turned just a little bit. There is no play in the steering and the car handles wonderfully. Any ideas what it is? What steps can I take to diagnose it?

Car: 1993 300D

try changing the power steering filter

http://catalog.peachparts.com/item.wws?sku=W0133-1640460&itempk=76438&mfr=Hengst&weight=0.20

normally there are noises when there isn't enough fluid. sounds like you have enough fluid, but you need more RPM to push it through your filter.

get a turkey baster and suck the reservoir on the pump dry and the filter is at the bottom.

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