GM Corvette 1984-1996 Repair Guide

Crankcase Ventilation System

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See Figure 1

The Positive Crankcase Ventilation (PCV) system is used to control crankcase blow-by vapors. The gases are recycled in the following way:

As the engine is running, clean, filtered air is drawn through the air filter and into the crankcase. As the air passes through the crankcase, it picks up the combustion gases and carries them out of the crankcase, through the PCV valve, and into the induction system. As they enter the intake manifold, they are drawn into the combustion chamber where they are reburned.

The most critical component in the system is the PCV valve. This valve controls the amount of gases which are recycled into the combustion chamber. At low engine speeds, the valve is partially closed, limiting the flow of gases into the intake manifold. As engine speed increases, the valve opens to admit greater quantities of gases into the intake manifold. If the PCV valve becomes clogged, the system is designed to allow excessive amounts of blow-by gases to back flow through the crankcase tube into the air cleaner to be consumed by normal combustion.



Click image to see an enlarged view

Fig. Fig. 1: Typical Positive Crankcase Ventilation (PCV) system airflow schematic-except 5.7L (VIN J) engine

The Positive Crankcase Ventilation (PCV) system must be operating correctly to provide complete removal of the crankcase vapors. Fresh air is supplied to the crankcase from the air filter, mixed with the internal exhaust gases, passed through the PCV valve and into the intake manifold.

The PCV valve meters the flow at a rate depending upon the manifold vacuum. If the manifold vacuum is high, the PCV restricts the flow to the intake manifold. If abnormal operating conditions occur, excessive amounts of internal exhaust gases back flow through the crankcase vent tube into the air filter to be burned by normal combustion.

TESTING



Never operate an engine without a PCV valve or a ventilation system, except as directed by testing procedures, for it can become damaged.

Incorrect operation of the PCV system can cause multiple driveability symptoms.

A plugged valve or hose may cause:



Rough idle
 
Stalling or slow idle speed
 
Oil leaks
 
Sludge in engineA leaking valve or hose would cause:
 
Rough idle
 
Stalling
 
High idle speed
 

PCV Valve
  1. Remove the PCV valve from the intake manifold or valve cover.
  2.  
  3. Run the engine at idle.
  4.  
  5. Place your thumb over the end of the valve. Check for vacuum. If there is no vacuum at the valve, check for plugged valve or vacuum lines.
  6.  
  7. Shut off the engine. Shake the valve and listen for the rattle. If valve doesn't rattle, replace it.
  8.  

System Functional Check
  1. Check the crankcase ventilation valve for correct application.
  2.  
  3. Run engine until normal operating temperature is obtained.
  4.  
  5. Block off crankcase ventilation system fresh air intake passage.
  6.  
  7. Remove the engine oil dipstick and install a vacuum gage on the dipstick tube.
  8.  
  9. Run the engine at 1500 rpm for 30 seconds, then read the vacuum gage while at 1500 rpm. If vacuum is present, the crankcase ventilation system is functioning properly. No vacuum indicates the engine may not be sealed and/or is drawing in outside air. Check valve cover and oil pan gaskets for leaks and repair, as required. If the vacuum gage registers a pressure or the vacuum gage is pushed out of the dipstick tube, check for the correct crankcase ventilation valve, a plugged hose or excessive engine blow-by.
  10.  

REMOVAL & INSTALLATION



PCV Valve
EXCEPT 5.7L (VIN J) ENGINES

See Figures 2, 3 and 4

  1. Disconnect the negative battery cable.
  2.  
  3. Unfasten the hose clamps, if necessary, then disconnect the hoses from the PCV valve.
  4.  
  5. Remove the PCV valve from the grommet in the valve cover.
  6.  



Click image to see an enlarged view

Fig. Fig. 2: Location of the PCV valve and related components-1987 vehicle shown



Click image to see an enlarged view

Fig. Fig. 3: PCV valve mounting-1990 5.7L (VIN 8) engine



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Fig. Fig. 4: Exploded view of the PCV valve and related hoses-5.7L (VIN P and 5) engines

To install:
  1. Insert the PCV valve into the grommet in the valve cover.
  2.  
  3. Connect the hoses to the PCV valve, then install the hose clamps, if equipped.
  4.  
  5. Connect the negative battery cable.
  6.  

5.7L (VIN J) ENGINE

See Figure 5

This engine is equipped with dual PCV valves.

  1. Disconnect the negative battery cable.
  2.  
  3. Unplug the PCV molded vacuum hose.
  4.  

Make sure to note the position of the PCV valves, because they are not interchangeable.

  1. Remove the PCV valve(s).
  2.  



Click image to see an enlarged view

Fig. Fig. 5: Schematic of the PCV air flow and valve location-5.7L (VIN J) engine

To install:
  1. Place the PCV valve(s) into the proper location.
  2.  
  3. Attach the molded vacuum hose to the valve(s).
  4.  
  5. Connect the negative battery cable.
  6.  

Cylinder Case Ventilation Cover
5.7L (VIN J) ENGINE

See Figures 6 and 7

  1. Take your vehicle to a reputable repair shop and have the A/C system discharged using the proper equipment.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the intake plenum assembly.
  6.  
  7. Tag and disconnect the ignition wires from the coil pack.
  8.  
  9. Remove the bolts retaining the ignition coil pack bracket to the ventilation cover and cylinder case.
  10.  
  11. Detach the coil pack electrical connectors, then remove the coil pack from the vehicle.
  12.  
  13. Tag and disconnect the vacuum hoses from the vacuum reservoir.
  14.  
  15. Remove the nuts and washers retaining the vacuum reservoir to the ventilation cover, then remove the reservoir from the vehicle.
  16.  
  17. Tag and disconnect the vacuum hoses from the secondary air inlet solenoid valve.
  18.  
  19. Unfasten the screws retaining the secondary air inlet solenoid valve to the ventilation cover and remove the solenoid valve from the vehicle.
  20.  
  21. Tag and disconnect the vacuum hoses from the secondary air inlet valve actuators.
  22.  
  23. Unfasten the nuts securing the actuators to the brackets.
  24.  
  25. Remove the retaining clips, then remove the actuators from the vehicle.
  26.  
  27. Unfasten the screws retaining the control assembly covers to the actuator brackets, then remove the covers from the vehicle.
  28.  
  29. Remove the link assembly from the lever assembly.
  30.  
  31. Detach the electrical connectors from the Engine Coolant Temperature (ECT) sensor (ECM connected) and the engine coolant temperature gauge sensor.
  32.  
  33. Remove the ECT sensor, and the engine coolant temperature sensor gauge from the injector housing.
  34.  



Click image to see an enlarged view

Fig. Fig. 6: Location of the engine coolant temperature sensors-5.7L (VIN J) engine

  1. Remove the serpentine drive belt.
  2.  


WARNING
When removing the A/C compressor, be careful to avoid damaging the system.

  1. Remove the A/C compressor.
  2.  
  3. Disconnect the cylinder case ventilation hoses.
  4.  
  5. Unfasten the bolts/screws securing the cylinder case ventilation cover to the cylinder case.
  6.  
  7. Remove the cover and gasket from the vehicle. Thoroughly clean the gasket mating surfaces. Be careful not to gouge the machined aluminum surfaces when cleaning.
  8.  



Click image to see an enlarged view

Fig. Fig. 7: View of the cylinder case ventilation cover-5.7L (VIN J) engine

To install:
  1. Position the gasket, then install the cylinder case ventilation cover and secure with the retaining bolts. Tighten to 89 inch lbs. (10 Nm).
  2.  
  3. Attach the cylinder case ventilation hoses.
  4.  
  5. Install the A/C compressor and secure with the retaining bolts.
  6.  
  7. Apply Loctite® 565 to the sensors, then install the engine coolant temperature sensors. Attach the electrical connectors.
  8.  
  9. Instlal the link assembly onto the lever assembly.
  10.  
  11. Install the actuator covers and screws, then install the actuator and secure with the retaining clips.
  12.  
  13. Install the nut retaining the actuators to the brackets.
  14.  
  15. Connect the vacuum hoses onto the actuators.
  16.  
  17. Install the solenoid valve and screw.
  18.  
  19. Install the vacuum reservoir tank, washers and nuts onto the ventilation cover. Tighten the nuts to 45 inch lbs. (5 Nm).
  20.  
  21. Attach the electrical connectors to the coil pack. Install the nuts retaining the coil pack bracket and tighten to 89 inch lbs. (10 Nm).
  22.  
  23. Connect the spark plug wires to the ignition coil.
  24.  
  25. Instlal the plenum assembly.
  26.  
  27. Connect the negative battery cable.
  28.  
  29. Take the vehicle to a reputable repair shop to have the A/C system recharged.
  30.  

Cylinder Case Ventilation Baffle
5.7L (VIN J) ENGINE

See Figure 8

  1. Remove the cylinder case ventilation cover, as outlined earlier in this section.
  2.  
  3. Unfasten the bolts securing the ventilation baffle to the cylinder case, then remove the baffle from the vehicle.
  4.  



Click image to see an enlarged view

Fig. Fig. 8: The cylinder case ventilation baffle is located under the ventilation cover-5.7L (VIN J) engine

To install:
  1. Apply Loctite® 262 to the baffle retaining bolt threads.
  2.  
  3. Install the baffle and secure with the retaining bolts.
  4.  
  5. Instlal the cylinder case ventilation cover.
  6.  

 
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