Hi, since replacing the power steering pump (cdti 1.9 150) when cold the pump is very noisy, it sounds.like it is sucking on.air almost, until you turn the wheel when the noise stops. When the wheel returns to straight ahead the noise returns. Once you have driven the car a little the noise goes altogether. I have bled it many times and the pump supplier suggests there is air entering the system, I can not see any external leaks. Any help greatly appreciated, Gaz.