Chrysler Front Wheel Drive Cars 6-CYL 1988-1995 Repair Information

Positive Crankcase Ventilation (PCV) System


See Figures 1, 2, 3 and 4

Engine crankcase pressure and emissions are vented into the combustion chambers through the Positive Crankcase Ventilation (PCV) system. The PCV system consists of a crankcase filter, a PCV valve, and hoses to complete a vacuum circuit.

The ventilation system operates by manifold vacuum. Air is drawn through the crankcase inlet filter and into the crankcase. The air is then circulated through the engine and drawn out through the PCV valve and into a passage in the intake manifold, becoming part of the calibrated air/fuel mixture drawn into the combustion chamber. It is then burned and expelled with the exhaust gases. The PCV system should have enough volume to overcome crankcase pressure created by piston backwash.

If a PCV system becomes plugged, the crankcase pressure will increase and force engine oil past the piston rings creating oil consumption. Blockage of the PCV system can occur at the vacuum source coupling, the PCV valve, the crankcase filter or a collapsed hose.

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Fig. Fig. 1: The PCV valve is mounted in the rocker arm cover on 1988-92 3.0L engines-except Premier and Monaco vehicles

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Fig. Fig. 2: PCV valve mounted in the intake manifold-1993-95 3.0L engines (except Premier and Monaco)

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Fig. Fig. 3: The PCV valve is located between two vacuum hoses on all 3.3L and 3.8L V6 engines

Chrysler Corporation recommends that a PCV valve not be cleaned. A new Mopar or equivalent PCV valve should be installed when servicing is required. Over a period of time, depending on the environment where the vehicle is used, deposits build up in the PCV vacuum circuit. The PCV system should be inspected at every oil change. Service the PCV system if engine oil is being discharged into the air cleaner. Chrysler recommends on replacing the PCV valve with a new one every 60,000 miles (96,000 km), unless the vehicle is driven under severe conditions, in which case, the PCV valve should be changed every 30,000 miles (48,000 km).


PCV Valve

To inspect the system pull (3.0L engine-equipped vehicles have a screw in type) the PCV valve out of the crankcase vent module, valve cover, or crankcase vent valve hose and shake it. If the valve rattles, this is a partial indication that it is okay; if there is no sound, it must be replaced and the PCV hose cleaned by spraying solvent (such as a carburetor cleaner type of solvent) through it.

If the valve rattles, you should still check the PCV valve with the engine idling. Pull it out of the vent module and place your finger or thumb over the end to stop air flow. You should feel some suction, and the engine speed should drop slightly. If there is no suction, or if the engine idle speeds up and smooths out considerably, replace the valve. Inspect the PCV hose and clean it by spraying solvent through it, if the inside is coated with gum and varnish.

Check the vacuum at the PCV inlet (from the rocker arm cover to the air cleaner) tube, as well. Disconnect this tube from the air cleaner and loosely hold a piece of paper over the tube. After about a minute, enough vacuum should build up to cause the paper to be sucked against the opening with a noticeable amount of force. This test proves whether or not the suction side of the system is clear.

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Fig. Fig. 4: Check for suction at the PCV valve while the vehicle is idling

Regardless of PCV valve or system performance, the valve itself should be replaced at specified intervals. At this time, you should inspect the hoses for clogging and spray a small amount of a safe cleaning solvent designed for this purpose through the hoses to remove any accumulated sludge or varnish.

Crankcase Filter

On all equipped models, the air drawn into the PCV system passes through a foam or metal mesh and foam filtration system. At the maintenance interval when PCV valve replacement is required, you should remove this element (or these elements) and replace it (or them). These elements are typically located in a corner of the air cleaner housing where you can see them as soon as the air filter element has been removed. If they become clogged before the normal service interval, they may be cleaned in a solvent such as kerosene and then coated with engine oil. When the car has reached the normal maintenance interval for the PCV system, these filters should be replaced.