Sounds like leaking rack seals. To confirm, go to where the inner tie rods attach to the rack. If you find fluid there most likely it is the seals leaking. Before rack replacement consider this alternative. Do you know what type of fluid is in the system now? If it isn’t synthetic, it is worth trying a flush of the PS system and replacing with a synthetic PS fluid compatible with your PS system. Synthetic fluid will clean and rejuvenate the seals and perhaps stop your leak.

Quick story - my 95 850 also developed a leaky rack. It was the rack seals leaking (common on older Volvo racks). So I flushed it out gradually using a turkey baster and replaced the old fluid with Mobil 1 synthetic ATF. After about a month or so the leak disappeared. I did have to repeat this process about once a year during the reminder of my ownership. Well worth it and worlds cheaper than a rack replacement! You might want to check if Mobil 1 ATF is okay for your PS system. My guess is yes as your car is only 8 years newer than my 850. If so, a cheap and easy fix!!
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Will I buy another Volvo??? We'll see....