Volvo engines from 99 on use a redesigned oil pan and oil cooler. There is a steel tube inside the pan that carries oil between the pump and the cooler on the back side of the pan. There are o-rings that seal each end of this tube. The o-rings have a tendency to blow out of the cavity, allowing air into the system. The early symptoms are bubbles on the dip stick, followed by noisy valves then flickering oil pressure lamp. The repair involves dropping the pan and replacing the o rings with upgraded parts. There is a T.S.B. regarding this problem, which affects a wide range of turbo and non turbo 5 and 6 cyl engines, however, no recalls.