GM 6.5L V8 – Crankcase Ventilation System

The crankcase ventilation system uses the open areas inside the engine cylinder case and right cylinder head to transfer the gases caused from combustion blow-by into the right rocker arm cover area. At that location, a Crankcase Depression Regulator Valve (CDRV) controls the entry of gases into the intake manifold.
The CDRV has an inlet fitting that connects to the right rocker cover, using a grommet (see Figure 6-19). It has an outlet fitting that attaches to a fitting on the turbocharger inlet duct with a combination of pipe, hoses and clamps.

Inside the CDRV, a spring holds open a valve plate that connects to the CDRV body with a flexible diaphragm. The valve plate is capable of restricting the outlet passage to the turbocharger air inlet duct when airflow pulls it closed against the force of the spring.
When the engine is running at idle speed, the airflow past the CDRV outlet passage may not be great enough and crankcase pressure could be 1 inch H20 (see Figure 6-20, view A).
At higher engine speeds, the valve closes to provide more restriction (see Figure 6-20, view B). This prevents the movement of oil vapors into the intake manifold by limiting the crankcase vacuum (measured at 2,000 rpm to be between 2 and 5 inches H O).
See page 6-24 for information about the crankcase pressure checking procedure.


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