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Cylinder Leakage Test

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Tools Required

    CAUTION: Refer to Battery Disconnect Caution in Cautions and Notices.
    IMPORTANT: A leakage test may be performed to measure cylinder/combustion chamber leakage. High cylinder leakage may indicate one or more of the following:
    • Worn, burnt, or stuck valves
    • Broken valve springs
    • Incorrect valve lash
    • Damaged valve train components
    • Damaged piston
    • Worn piston rings
    • Worn or scored cylinder bore
    • Damaged cylinder head gasket
    • Cracked or damaged cylinder head
    • Cracked or damaged engine block
  1. Disconnect the battery ground negative cable.
  2. Remove the glow plugs.
  3. Rotate the crankshaft to place the piston in the cylinder being tested at Top Dead Center (TDC) of the compression stroke.
  4. Install J 35667-9  and J 35667-A  .
    5. Fig 1: Testing Cylinder Leakage
    GM1211555Courtesy of GENERAL MOTORS CORP.
    IMPORTANT: It may be necessary to hold the crankshaft balancer bolt to prevent the engine from rotating.
  5. Apply shop air pressure to J 35667-A  and adjust according to the manufacturers instructions.
  6. Record the cylinder leakage value. Cylinder leakage that exceeds 25 percent is considered excessive and may require component service. In excessive leakage situations, inspect for the following conditions:
    • Air leakage sounds at the intake manifold tube, may indicate a worn, stuck or burnt intake valve, broken valve spring, incorrect valve lash or damaged valve train components.
    • Air leakage sounds at the exhaust system tailpipe may indicate a worn, burnt, or stuck exhaust valve, broken valve spring, incorrect valve lash or damaged valve train components.
    • Air leakage sounds from the crankcase, oil level indicator tube, or oil fill tube may indicate worn piston rings, a damaged piston, a worn or scored cylinder bore, a damaged engine block or a damaged cylinder head.
    • Air bubbles in the cooling system may indicate a damaged cylinder head or gasket.
  7. Perform the leakage test on the remaining cylinders and record the values.
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