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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 271 (Engine Controls - Basic Diagnostic Procedures - 3.1L) >> Preliminary Inspection & Adjustments >> Mechanical Inspection >> Cylinder Leakage

Cylinder Leakage

WARNING: This page is about a different car, the 2003 Pontiac Grand Prix, 2003 Chevrolet Malibu, and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
WARNING: Before servicing any electrical component, the ignition key must be in the OFF or LOCK position and all electrical loads must be OFF, unless instructed otherwise in these procedures. A tool or equipment could easily come in contact with a live exposed electrical terminal, also disconnect the negative battery cable. Failure to follow these precautions may cause personal injury and/or damage to the vehicle or its components.

With the use of air pressure, a cylinder leakage test will aid in the diagnosis. Use the cylinder leakage test in conjunction with the engine compression test in order to isolate the cause of leaking cylinders.

  1. Disconnect the negative battery cable.
  2. Remove the spark plugs.
  3. Install the Cylinder Leakdown Tester (J 35667-A), or equivalent.
  4. Measure each cylinder on the compression stroke, with both valves closed.
    5. NOTE: Hold the crankshaft balancer bolt to prevent piston movement.
  5. Following the manufacturer's instructions, apply air pressure, using the cylinder leakdown tester.
  6. Record the cylinder leakage readings for each cylinder.
    • Normal cylinder leakage is from 12 to 18 percent.
    • Make a note of any cylinder with more leakage than the other cylinders.
    • Any cylinder with 30 percent leakage or more requires service.
  7. Check the 4 primary areas to properly diagnose a leaking cylinder.
  8. If air is heard from the intake or exhaust system, perform the following procedure:
    • Remove the valve rocker arm cover of the suspect cylinder head. Ensure that both valves are closed. Check the cylinder head for a broken valve spring.
    • Remove and inspect the suspect cylinder head. See appropriate article in ENGINES.
  9. If air is heard from the crankcase system at the crankcase, oil filler tube, perform the following procedures. See appropriate article in ENGINES for removal and inspection procedures:
    • Remove the piston from the suspect cylinder.
    • Check the piston and connecting rod assembly.
    • Check the engine block.
  10. If bubbles are found in the radiator, perform the following procedures. See appropriate article in ENGINES for removal and inspection procedures:
    • Remove and inspect both cylinder heads.
    • Check the engine block.
  11. Remove the cylinder leakdown tester.
  12. Install the spark plugs.
  13. Connect the negative battery cable.
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