Mooo noise from steering

[Pantelis Giamarellos]

Fellow listers,

Today I have noticed that when switching the car on and turn the steering
wheel left or right a mooo-ing noise with some high resonance transmited to
the steering wheel.

When the engine is warmed up the noise and resonance disappear.

Pentosin level is OK.

There is some pentosin leaking (topping up a bit of pentosin about once
every two months) but no majot leaking problem.

Car is a 1995 model year RS2
Thanks for your suggestions.

Take care
Pantelis