have you bled the pump, to do it just leave the PAS tank cap off, engine running, and turn the steering lock to lock a few times, and make sure there is enough fluid in.

have a look at the PAS cooler rad (in front of the rad, behind the bumper) to see if it is leaking.

if you need a new rack, i had a recon rack which failed after a few months (and i know of someone else who had it happen on two racks).

i now have another recon rack on which cost £120 but i cant remember the brand name, the garage who fitted it said they fit them regularly and have no probs with them.

the other option is get a 2nd hand rack from a low miler which is breaking, i got one off an st200 for £25 posted from a mondeo forum to keep for a spare!