A crankcase ventilation breach detection system of an internal combustion engine comprising: an internal combustion engine having a crankcase and an intake manifold; a positive crankcase ventilation valve in fluid communication between the crankcase and intake manifold that regulates the flow of blow-by-gas from the crankcase to the intake manifold; a crankcase ventilation tube in fluid communication with air from an air intake and the blow-by-gas and subdividing into a flow control system; wherein the flow control system comprises: a plurality of parallel conduits (132, 134, 136) comprising a first conduit having a normally closed check valve controlling flow through the first conduit, the normally closed check valve opening under a first preselected pressure drop in a first direction of flow from the air intake to the crankcase, and a second conduit (132, 136) having a second check valve that opens under a second preselected pressure drop in a second direction of flow from the crankcase to the air intake, characterized in that the second preselected pressure drop is the same or lower than the first preselected pressure drop; and a pressure sensor positioned between the parallel conduits (132, 134, 136) and the crankcase, wherein detection of no pressure drop by the pressure sensor indicates a breach in the system, wherein the internal combustion engine has a turbocharger (114, 115) and the crankcase ventilation tube connects upstream of the compressor of turbocharger an internal combustion engine having a crankcase and an intake manifold; a positive crankcase ventilation valve in fluid communication between the crankcase and intake manifold that regulates the flow of blow-by-gas from the crankcase to the intake manifold; a crankcase ventilation tube in fluid communication with air from an air intake and the blow-by-gas and subdividing into a flow control system; wherein the flow control system comprises: a plurality of parallel conduits (132, 134, 136) comprising a first conduit having a normally closed check valve controlling flow through the first conduit, the normally closed check valve opening under a first preselected pressure drop in a first direction of flow from the air intake to the crankcase, and a second conduit (132, 136) having a second check valve that opens under a second preselected pressure drop in a second direction of flow from the crankcase to the air intake, characterized in that the second preselected pressure drop is the same or lower than the first preselected pressure drop; and a pressure sensor positioned between the parallel conduits (132, 134, 136) and the crankcase, wherein detection of no pressure drop by the pressure sensor indicates a breach in the system, wherein the internal combustion engine has a turbocharger (114, 115) and the crankcase ventilation tube connects upstream of the compressor of turbocharger a plurality of parallel conduits (132, 134, 136) comprising a first conduit having a normally closed check valve controlling flow through the first conduit, the normally closed check valve opening under a first preselected pressure drop in a first direction of flow from the air intake to the crankcase, and a second conduit (132, 136) having a second check valve that opens under a second preselected pressure drop in a second direction of flow from the crankcase to the air intake, characterized in that the second preselected pressure drop is the same or lower than the first preselected pressure drop; and a pressure sensor positioned between the parallel conduits (132, 134, 136) and the crankcase, wherein detection of no pressure drop by the pressure sensor indicates a breach in the system, wherein the internal combustion engine has a turbocharger (114, 115) and the crankcase ventilation tube connects upstream of the compressor of turbocharger