Description & Operation: 318i
A sealed system is used which does not allow entry of fresh air into crankcase. Crankcase vapors and blow-by gases are drawn from the crankcase up to the valve cover and into a hose which runs to the intake manifold side of the air cleaner. Gases then travel through the intake manifold to combustion chambers for burning. Running engine creates crankcase vacuum; being a sealed system, no gases or vapors escape into atmosphere.