Closed crankcase ventilation: Notes
The combustion gases passing the piston rings are collected in the crankcase and must be discharged from the engine through the crankcase ventilation. This is firstly to prevent excessive pressure in the crankcase and secondly to vent the water vapour and hydrocarbons from combustion. As the crankcase gases contain hydrocarbons, they cannot be discharged into the atmosphere but must be recycled into the cylinders to be combusted. The engine crankcase ventilation system is therefore a closed system.
The crankcase gases formed are first passed to an oil trap integrated in the timing cover where the gases are separated from the oil. The oil runs back to the engine oil pan while the gases are passed to the engine cylinders.
The crankcase ventilation system works in two different ways, depending on whether the engine is working at low or high load.