Lincoln Mark VIII PCV Valve Replacement Cost

As the engine operates, small fires inside each engine cylinder create pressure that pushes the engine piston down, toward the crankshaft, and some combustion gases from the fire in the cylinder are able to get around the piston, and enter the crankcase. Also, heat from the engine causes the air inside the crankcase to expand. If this condition were left untreated, the engine would develop leaks, and would suffer severe inefficiency, if it ran at all. To prevent this situation, the crankcase ventilation system connects the crankcase to the intake manifold. The intake manifold is constantly under vacuum as the engine sucks in air, so when the crankcase ventilation valve is installed, the hot gases are sucked from the engine crankcase, and burned in the engine as fuel.

Rough idling, lack of power, engine oil leaks, engine burning oil, and illumination of the check engine light are all possible if the PCV valve has clogged. If the check engine light comes on, the on-board diagnostics (OBD) trouble codes will most likely relate to manifold vacuum, air and fuel mixture, PCV system, mass airflow sensor readings, and exhaust and emissions readings. These are all affected in the event the PCV valve is clogged, is stuck fully open, or is stuck fully closed, however, if the valve is stuck fully open, the engine oil seals are not in danger of overpressure.

Driving with the PCV valve stuck closed or clogged is not recommended. If the vehicle must be driven, keeping the engine speed low is the safest bet, as this will also decrease the amount of pressure in the crankcase. If the PCV valve is stuck open, there is no harm in driving, however, the vehicle may experience poor fuel mileage, vibrations, and the dreaded check engine light as the computer registers this condition as a vacuum leak.