Checking PCV Valve Function

2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8SECTION Checking PCV Valve Function
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2003 GMC Sonoma, 2003 GMC Safari, 2003 GMC Jimmy, 2003 Chevrolet S10 Pickup, and 2003 Chevrolet Blazer. However, it is still accessible from the selected car via links, so may be relevant.
  1. Disconnect PCV valve vacuum hose from cylinder head cover. Run engine at idle. Place thumb over open end of PCV valve vacuum hose to check for vacuum. If vacuum does not exist, check for obstruction in source vacuum supply. If source vacuum supply is okay, replace PCV valve.
  2. Turn ignition off. Remove PCV valve. Shake valve and listen for rattle of check valve inside PCV valve. If a clear rattle is not heard, replace PCV valve.
  3. Visually inspect valve for varnish or deposits that may make PCV valve operation sticky or restricted, or cause incomplete seating of valve. Replace as necessary.
  4. Engine must be sealed for PCV system to function as designed. If leakage, sludging or dilution of oil is noted and PCV system is functioning properly, check engine for cause and repair as required to ensure PCV system will continue to function properly.
  5. An engine operating without any crankcase ventilation can be damaged, so it is important to replace PCV valve and air cleaner breather (if equipped) at regular intervals (at least every 30,000 miles). Check all hoses and clamps for failure or deterioration.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.