One problem related to steering rack has been reported for the 1999 Volvo S80. The most recently reported issues are listed below.
Dealer advised car had a defective steering rack, which was replaced along with associated "o" rings. Eleven days after warranty work was completed, owner was driving vehicle when the car caught on fire. Fire was attributed to a "crimped" o-ring. Dealer replaced the o-ring and has been test driving vehicle since then. The o-ring has crimped again recreating the same scenario. Owner is now in the middle between dealer and Volvo pointing fingers at each other.