This system draws crankcase vapors that are formed through normal combustion into the intake manifold and subsequently into the combustion chamber to be burned. Fresh air is introduced to the crankcase by a hose connected to the carburetor air cleaner or a vented oil filler cap, on older models. Manifold vacuum is used to draw the vapors from the crankcase through a PCV valve and into the intake manifold. Vented and nonvented filler caps were used on various models until 1968, after which only nonvented caps were used.
Inspect the PCV system hose and connections at each tune-up and replace any deteriorated hoses. Check the PCV valve at every tune-up and replace it every 24,000 miles. For details on PCV valve replacement, refer to .