Few things. Neglected flame traps = blown rear main engine seal. It's hard to get to on the 850 so is often neglected. A/C evaporator failure is pretty common. $1000+ as dash and half the engine need to come out. No tranny filter and no recommended ATF change by volvo = a lot with the origional ATF still in. Not good. ABS module common problem although they can be rebuilt for about $100. or so by a guy in CA. His name escapes me at the moment. THey are overall great cars and fun to drive although somewhat maintance heavy. If you can handle a lot of the routine stuff, they aren't bad at aall.

bl