Lost power steering at low revs

[wayno]

I have a manual 2001 mercedes c220 cdi recently when turning with the wheels full lock i lost all power steering no liquids leaked form the engine block or belts came off. when i rev the engine to 2.5 rpms the power steering works but makes a wineing noise why is this also when looking for the steering fluid i can`t find the power steering reservoir or see does it need toping up. Thanks to any one that can shed light on this subject.

 

[Ellsy Tanners]

Hello, its under the engine cover on the right of the engine as you look at it. A black resovoir.