Mercury 7L3Z-6A666-A Valve Assembly

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The Positive Crankcase Ventilation (PCV) system reduces emissions by circulating fresh air from the air cleaner through the crankcase, mixing with gases, and rerouting through a PCV valve to the intake manifold. The system includes a PCV valve, a fresh air inlet, and vacuum hoses. The PCV valve restricts flow to maintain idle quality. If anything odd occurs, the system allows excess gases to flow back into the air cleaner. It is required that regular checking and replacement of the PCV valve happens.

The PCV valve on 5.4L engines is built into the valve cover and only needs to be replaced if defective. On other models, it is located on the valve cover or intake manifold. To replace it, disconnect the electrical connector and hose. Rotate and remove the valve. For 5.4L models, remove the fasteners and valve. Installation is the reverse, using a new 0-ring.

It should be replaced.

Yes, it is necessary to check and replace the PCV valve and filter.

The oil filler cap, hoses, or valve cover gasket may be leaking, or the PCV valve may be bad. It is recommended to check for vacuum leaks at the valve, filler cap, and all hoses.