The high pressure of combustion in the cylinder forces some of the gases past the piston ring into the crankcase. To prevent dilution of the oil and acid formation these gases must be removed. The positive crankcase ventilation (PCV) system removes these gases without discharging them into the atmosphere. Through the PCV valve, air is pulled out of the crankcase and diverted to the intake system. Clean air must be brought into the crankcase to complete the flow loop.