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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 282 (Engine Controls - Basic Diagnostic Procedures - 3.8L) >> Preliminary Inspection & Adjustments >> Mechanical Inspection >> Cylinder Leakage

Cylinder Leakage

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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. If 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. The cylinder leakage test may be used in conjunction with the engine compression test, to isolate the cause of leaking cylinders.

  1. Disconnect the negative battery cable.
  2. Remove the spark plugs.
  3. Install the Cylinder Head Leakdown Tester (J 35667-A), or equivalent.
  4. Measure each cylinder on the compression stroke, with both valves closed.
  5. Apply air pressure, using the cylinder head leakdown tester, following manufacturer's instructions. It may be necessary to hold the crankshaft balancer bolt, to prevent piston movement.
  6. Record the cylinder leakage readings for each cylinder.
    • Normal cylinder leakage is from 12-18 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 procedures. See appropriate article in ENGINES:
    • 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 the suspect cylinder head and inspect.
  9. If air is heard from the crankcase system at the crankcase, oil filler tube, perform the following procedure. See appropriate article in ENGINES for procedures and inspection specifications:
    • 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 procedure. See appropriate article in ENGINES for procedures and inspection specifications:
    • Remove both cylinder heads and inspect.
    • Check the engine block.
  11. Remove the cylinder head leakdown tester.
  12. Install the spark plugs.
  13. Connect the negative battery cable.
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