a friend owns a duratec 1.8 diesal estate thing, i checked it oover for him the other day and it does a really weird thing, when you turn either way it makes a loud whining noise however it does not do it when the wheel is turned in idle when standing in neutral, when idling the pump is quiet and when full locked doesnt make anyomre noise than it normally should under ful load its only whilst driving when taking a heavy turn ie a roundabout or turning in or out of a road, i was thinking the pumps fked or a spool valve somehere not opeining all the way so possibly the rack but they are expensive bits so need to try and nail it first time around

 

what car is it?the mondeos s max etc suffered with breaking up racks which would block the filter in the reservoir.try cleaning that out first and checking for swarf in it