Is this Power steering noise normal? Does yours make same noise?

[X5only]

Hi,

My X5 4.4 with 48.5K miles on it is making this power steering noise when steering is turned all the way to the left or right. It sounds like "nnng'eeeeeeee" and as soon as you start turning it the other way the noise goes away. Is this normal? I checked the powering steering fluid at the reservior and fluid level is upto top line on the little dip stick. I also see dusty traces of fluid on the sides of reservoir and on the shield at the bottom of the engine. I asked the technician at dealer and he says that's normal for noise and the dusty traces of fluid is residue from reservior and are not leaks. I was a bit sceptical although there're no drippings on the floor or the pipes underneath the reservoir. I checked it closely. Is that right? Does yours make same noise or has tell-tale traces of dusty fluid on shield guard at bottom of engine? I looked closely at service history of the vehicle and no indication there has been issues with power steering system. But I want re-assurance from other users that there's make the same noise.

Thanks!