On the 850s and S70s, the front struts tend to make noise due to cracked or torn spring retainer cups located at the top of the strut (you can see them when you open the hood). It may not be easy to spot, it all depends on how badly damaged they are. I just made the discovery on my own car last week--on one side, it was as small as a hairline. Another common suspension problem on this model, are the sway-bar endlinks. They too fail and cause a clunking noise--had the passenger side endlink replaced on my own car about a month ago. Take a good look at the spring retainer cups first and go from there. Good luck with it.