Power steering pump or rack problem

[VIW28 29]

Been having issues with my power steering pump in that it's been making the "scringing" noise and also sending all the oil back up to the power steering bottle to the point where it all just overflows and spills out the top.

I replaced the pump with another second hand one and it's doing the same thing again.

I wondered one of two things;

1. Could I have been so unlucky as to have replaced the original with another dud pump?

2.Or, is this a characteristic of a power steering rack being shot?

Anyone with any simlar issues or experiences, your input would be appreciated.

[VIW28 29]

By the way, it is a 12v '96 VR