Checking engine internal pressure: Notes

As a result of the combustion pressure gases are forced from the combustion chamber between the cylinder barrel and piston into the crankcase.

To prevent considerable excess pressure from being created in the crankcase, gases are directed by the vacuum in the intake area through the crankcase ventilation system into the intake area.

A pressure control valve limits the vacuum.

Faults in the crankcase ventilation system causes a high vacuum or excess pressure in the crankcase.

The function of the crankcase ventilation system can be tested by means of pressure measurement.