What is the importance of crankcase ventilation system in a engine ?

A crankcase ventilation system is one way to escape gases from the crankcase to outside of an internal combustion engine. A clogged or inoperative crankcase ventilation system will lead to poor engine performance; rapidly wear out rings and cylinder bores, stick rings, valve lifters, valves, and cause sludge formations which can clog oil passages throughout the engine.

Sometimes combustion pressure passes leak through the piston rings into the crankcase. If an engine’s breathing system should become blocked or restricted, the crankcase will pressurize causing any one or more of the following problems:

1.      The oil/air mix will force its way out through any other convenient exit e.g. oil seals, dip stick etc.

2.      The efficiency of the oil control rings will be reduced creating increased oil consumption.

3.      Impurities such as water vapor and acids (by products of combustion) will build up and contaminate the oil causing slugging and increased engine wear.

4.      As a consequence of the weakened fuel charge, detonation or ‘pinking’ will ensue. To compensate, the ignition will need retarding resulting in further power loss.

Also its a non return path which just allow to flow gas outside but prevnet to return enter exhaust gas.