Finbin

Hi looking for help.
Car is UK Impreza Turbo 1999 (V reg), standard car.
Power Steering pump was making a noise, as I had a spare one from a previous Impreza, I swapped pumps. But after a couple minutes test drive the power steering stopped working. I swapped back to the original pump but the same thing happened after a slightly longer test drive.
I then removed the original pump again, whilst doing this I noticed the oil had very fine metal particles in it!!!
I drained all the original fluid, removed the rear of the pump, cleaned inside, and couldn’t see any major faults inside. Refitted, filled with fluid, bleed system and tried again, but still no power steering.
I think it is very strange that two pumps should be faulty and are they that precision engineered??
Am I now looking for a new pump? or is there a repair kit for them?
Any help would be good