Piston Engines

The Mazda closed crankcase ventilation system consists of a PCV valve and various connecting hoses. On piston engine applications, a hose leads from the valve cover, through a PCV valve and into the intake manifold below the carburetor. There is another hose which leads from the air cleaner into the valve cover to supply fresh air to the crankcase when engine vacuum overcomes crankcase pressure.

Air flows through the air cleaner-to-valve cover hose, mixes with the blow-by gases and crankcase vapors, and is drawn out through the ventilation hose and the in-line PCV valve and back into the engine to be reburned with the incoming air/fuel mixture. The PCV regulates the amount of air flow to meet changes in operating conditions of the engine.