Chrysler Neon 1995-1999 Repair Guide

Crankcase Ventilation System

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OPERATION



See Figures 1, 2 and 3

All vehicles are equipped with a Positive Crankcase Ventilation (PCV) system. In this system, the intake manifold vacuum removes crankcase vapors and piston blow-by from the engine. The emissions pass through the PCV valve into the intake manifold where they become part of the set air/fuel ratio. They are burned and released with the exhaust gases. The air cleaner provides make up are when the engine does not have enough vapor or blow-by gases. In this system, fresh air does not enter the crankcase. The PCV system is composed of a PCV valve, oil separator (1998 engines only) and connecting hoses.

The PCV valve has a spring loaded plunger. The plunger meters the amount of crankcase vapors routed into the combustion chamber, depending upon intake manifold vacuum. When the engine is not operating or during engine backfire, the spring forces the plunger back against the seat, preventing vapors from flowing through the valve. When the engine is at idle or cruising, high manifold vacuum is present. At these times, manifold vacuum is able to completely compress the spring and pull the plunger to the top of the valve. There is minimal vapor flow through the valve in this position. During periods of moderate manifold vacuum, the plunger is only pulled part of the way back from the inlet, resulting in maximum vapor flow.



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Fig. Fig. 1: When the engine is off or backfiring, there is no vapor flow



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Fig. Fig. 2: During a condition of high manifold vacuum, there is a minimal amount of vapor flow



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Fig. Fig. 3: Maximum vapor flow exists when there is a moderate intake manifold vacuum

On 1998 engines, the PCV system also includes an oil separator. The crankcase vapors enter the bottom of the separator, then oil accumulated in the separator drains back into the crankcase from an outlet in the bottom of the separator. The PCV valve on these engines, connects to the separator and to intake manifold vacuum. Make-up air is provided to the separator by a hose attached to the air cleaner air tube.

COMPONENT TESTING



See Figure 4


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

  1. With the engine idling, detach the vapor hose from the PCV valve. 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.  



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Fig. Fig. 4: Check the PCV valve for vacuum at idle

  1. Attach the hose to the PCV valve. Disconnect the make-up air hose from the air plenum at the rear of the engine. Hold a piece of rigid paper loosely over the end of the make-up air hose.
  2.  
  3. After allowing about 1 minute for the crankcase pressure to decrease, the paper should draw up against the hose with a noticeable force. If the engine does not draw the paper against the grommet after installing a new valve, replace the valve hose.
  4.  
  5. Turn the engine OFF . Remove the PCV valve from the intake manifold, then shake the valve. The valve is OK if a rattling noise is heard as the valve is shaken.
  6.  
  7. 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.
  8.  

REMOVAL & INSTALLATION



PCV Valve

See Figures 5, 6, 7 and 8

  1. Disconnect the negative battery cable.
  2.  
  3. If necessary, use a pair of pliers to unfasten the crankcase hose retaining clamps, then disconnect the ventilation hoses from the PCV valve.
  4.  
  5. Remove the PCV valve from the camshaft (rocker) cover or the hose, as applicable.
  6.  



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Fig. Fig. 5: Location of the PCV valve and oil separator (intake manifold installed)-1998 vehicles



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Fig. Fig. 6: PCV valve and oil separator location (intake manifold removed)-1998 vehicles



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Fig. Fig. 7: Positive Crankcase Ventilation (PCV) valve and hose locations-1998-99 SOHC engines



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Fig. Fig. 8: Location of the PCV valve on a 1998-99 DOHC engine

To install:
  1. Install the PCV valve into the rocker cover or attach to the hose, as necessary.
  2.  
  3. Reconnect the ventilation hoses to the valve. If necessary, use a pair of pliers to secure the hose clamps.
  4.  
  5. Connect the negative battery cable.
  6.  

Oil Separator

See Figures 5 and 6

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the intake manifold from the vehicle as outlined in Engine and Engine Rebuilding of this guide.
  4.  

Constant tension hose clamps are used on the separator hoses. During removal and installation, you should use the special clamp tools (No. 8098), available for this purpose.

  1. Disconnect the PCV valve hose from the oil separator.
  2.  
  3. Unfasten the hose clamps, then detach the 2 hoses from the bottom of the separator.
  4.  
  5. Remove the 2 separator-to-block retaining bolts, then remove the separator from the vehicle.
  6.  

To install:
  1. Position the separator in the vehicle, and secure with the 2 retaining bolt.
  2.  

An identification number or letter is stamped into the tongue of the constant tension clamps. If you need to replace a clamp, make sure to get an original replacement clamp with a matching number or letter.

  1. Connect the 2 hoses to the bottom of the separator, then secure the hoses with the clamps.
  2.  
  3. Attach the PCV valve hose to the oil separator.
  4.  
  5. Install the intake manifold, as outlined in Engine and Engine Rebuilding of this guide.
  6.  
  7. Connect the negative battery cable.
  8.  

 
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