Abstract: A closed crankcase ventilation system which relies on a vacuum assist from the turbocharger inlet to suction blow-by gases from the crankcase. The system includes a coalescer/filter which is operative to filter any oil particles which may be entrained in the blow-by gases before they are released into the turbocharger inlet. A pop off valve is also included in order to prevent the engine crankcase from becoming over pressurized as a result of back pressure caused by either a plugged coalescer/filter or some catastrophic engine malfunction. Further included is a vacuum limiting valve which prohibits the vacuum assist produced by the air inlet to the turbocharger from producing too low of an absolute pressure, thereby preventing an imbalance in pressure across the seals of the turbocharger. The system further includes a bypass valve which also prevents the crankcase from becoming over pressurized by routing the flow of blow-by gases around the coalescer/filter if the pressure in the crankcase becomes too great.