Q: What is the purpose of the Positive Crankcase Ventilation (PCV) system and PCV Valve?A: The Positive Crankcase Ventilation (PCV) system reduces hydrocarbon emissions by directing blow-by gases and crankcase vapors into the intake manifold, where they're mixed with intake air before being drawn into the combustion chambers, where they're consumed along with the air/fuel mixture. This is achieved by circulating fresh air from the air filter housing through a series of hoses into the crankcase, where the fresh air mixes with blow-by gases before being drawn from the crankcase by intake vacuum, through the PCV valve then into the intake manifold. During idle and part-throttle conditions, intake manifold vacuum is high. Blow-by gases and crankcase vapors flow from the crankcase through the PCV valve and the crankcase ventilation hose into the intake manifold. The strong intake manifold vacuum also pulls fresh air from the air intake duct or the air filter housing through the fresh air inlet hose into the crankcase. There is no scheduled maintenance interval for the PCV valve or the PCV system hoses, but over time the PCV system might become less efficient as an oily residue of sludge builds up inside the PCV valve and the hoses. One symptom of a clogged PCV system is leaking engine seals. When crankcase vapors can't escape, pressure builds inside the bottom end and eventually causes engine seals to leak. Anytime that you're changing the oil filter, air filter, fuel filter, spark plugs, etc. It's a good idea to pull off the PCV hoses and inspect them. If the hoses are clogged, remove them and clean them out. If they're cracked, torn or deteriorated, replace them. Checking and replacement of the PCV valve are covered. It is mounted to the valve cover on all models.