Originally Posted by kolnerspieler

I had the same problem on my w210. When you rev the motor the steering works, but not at idle when you really need it.

I ended up just replacing the PS pump with a used pump that I pulled from a yard. I was lucky because I think the diesel has a different pump than the gassers so they are hard to find used.

The w210 does have problems with the PS pump as far as I know.