Description
Volvo uses a small in-line filter to manage positive crankcase ventilation on their 4 cylinder engines.
The ventilation system incorporates a small flame trap filter (PCV) to protect against possible crankcase explosions due to a backfire. This filter is overlooked in most workshop manuals and without periodic maintenance it will plug up with oil deposits and cause excessive crankcase pressure, which in turn cause significant oil leaks all over the engine. An additional contributor to this problem is the fact that on these models, the filter and filter holder are buried below the intake manifold and pretty tough to access.
We recommend checking the flame trap condition at every oil change.