The PCV system is designed to vent and control the pressures inside the engine. Any time you have moving parts in an enclosed space, such as inside your engine, you need to vent the assembly. If you don’t, excessive pressure builds up inside the system. PCV stands for Positive Crankcase Ventilation; in the case of the automotive engine, the PCV system is used to vent the crank case and control emissions.
Before the days of the PCV system, they used to vent engine pressure to the atmosphere via an oil draft tube. A problem with the PCV system can cause pressure to build up inside the engine. This excess pressure can aggravate existing engine oil leaks, so if you have a lot of oil leaks on your engine, it’s worth checking the operation of your PCV system. Consult your service manual for the procedures necessary to inspect and repair the PCV system on your vehicle.