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Crankcase Ventilation System Inspection/Diagnosis

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Crankcase Ventilation System Inspection/Diagnosis

Concern Action
DEFINITION: During normal operation the crankcase gases can be seen exiting from the hose at the oil separator.
The maximum crankcase pressure is 4 kPa or 16 in of water at 3,100 RPM measured at the oil level indicator tube.
Oil leak - external
  • Plugged or kinked crankcase ventilation system hoses
  • Damaged or loose crankcase ventilation system hoses
  • Valve rocker arm diaphragm covers loose
  • Oil separator oil drain hose damaged or loose
  • Too much crankcase pressure
PVC check valve (bottom of generator bracket) stuck closed
  • Valve closes when 1.47 kPa (0.213 psi) of crankcase pressure is applied from the crankcase side (bottom) of the valve.
  • Valve should allow oil to drain from the separator during idle and engine off conditions.
  • Inspect for proper operation by stopping engine and waiting 5 minutes to allow the oil to drain back into the crankcase. Remove the drain hose from the check valve. If more than residual oil (several drops) drains from the separator, replace the valve.
Odors Normal situation
Noise Cracked hoses
Smoke Internal engine failure
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