Positive Crankcase Ventilation: Description and Operation

Fig. 11 Closed crankcase ventilation system.:

Fig. 12 Closed crankcase ventilation system.:

Fig. 13 Closed crankcase ventilation system.:

Blow-by gasses are evacuated from the engine through a liquid/vapor separator mounted on the crankcase, Figs. 11 through 13. Manifold vacuum is applied to the liquid/vapor separator through a PCV valve. Ventilating air is drawn into the engine through a blow-by filter on the valve cover on Accord or through a tube to the main air cleaner on Civic, CRX and Prelude. The air is drawn down into the crankcase through the oil return passages by manifold vacuum, where it mixes with the blow-by gasses, and the blow-by gasses are drawn into the intake stream and burned during the normal combustion process. On some models, a heater hose containing engine coolant is built around the PCV valve to prevent it from icing during cold weather.