Chrysler Caravan/Voyager/Town and Country 1996-1999

Crankcase Ventilation System

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OPERATION



Crankcase vapors and piston blow-by from the engine is removed by intake manifold vacuum. The engine emissions pass through the PCV valve into the intake manifold where they become part of the calibrated air-fuel mixture. They are burned and expelled with the exhaust gases. When the engine cannot supply enough vapor or blow-by gases, make up air is provided by the air cleaner. In this system, fresh air does not enter the crankcase.

Positive Crankcase Ventilation (PCV) Valve

See Figures 1, 2 and 3



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Fig. Fig. 1: Cutaway view of a PCV valve with the engine off or during engine backfire, when there is no vapor flow



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Fig. Fig. 2: Cutaway view of a PCV valve during high intake manifold vacuum, when there is minimal vapor flow



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Fig. Fig. 3: Cutaway view of a PCV valve during moderate intake manifold vacuum, when there is maximum vapor flow

The PCV valve contains a spring loaded plunger. Based on intake manifold vacuum, this plunger meters the amount of crankcase vapors routed into the combustion chamber. The spring will seat the plunger when the engine is not operating or during engine backfire, which will prevent vapors from flowing through the valve.

High intake manifold vacuum is present when the engine is idling or cruising. During these times, the vacuum is strong enough to completely compress the spring, moving the plunger to the top of the valve which allows minimal vapor flow through the valve.

Maximum vapor flow through the PCV valve is produced during periods of moderate manifold vacuum, when the plunger is only partially pulled away from the inlet.

COMPONENT TESTING



See Figure 4


CAUTION
ALWAYS block the drive wheels and apply the parking brake any time you are performing a test or adjustment in which the engine must be running!



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Fig. Fig. 4: Checking the PCV valve for clogging

  1. With the engine idling, remove the PCV valve from its attaching point. If the valve is not obstructed, a hissing noise will be heard as air passes through the valve. Also, a strong vacuum should be felt when you place your finger over the valve inlet.
  2.  
  3. Turn the engine OFF . Remove the PCV valve from its attaching point, then shake the valve. The valve is OK if a rattling noise is heard as the valve is shaken.
  4.  
  5. If any of the previous tests fail, replace the PCV valve and/or hose and retest the system. Do not try to clean and reuse the old PCV valve. It should be replaced with a new one.
  6.  

REMOVAL & INSTALLATION



For PCV valve removal and installation procedures, refer to General Information & Maintenance of this repair guide.

 
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