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Cylinder Leakage Test

WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: 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.

A leakage test may be performed in order to measure cylinder/combustion chamber leakage. High leakage may indicate one or more of the following:

  1. Disconnect the battery ground negative cable.
  2. Remove the spark 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 the Cylinder Head Leakdown Tester (J 35667-A), or equivalent.
  5. Apply shop air pressure to the cylinder head leakdown tester and adjust according to the manufacturers instructions.
  6. Record the cylinder leakage value. Cylinder leakage that exceeds 25 percent in considered excessive and may require component service. In excessive leakage situations, inspect for the following conditions:
    • Air leakage sounds at the throttle body or air inlet hose that may indicate a worn or burnt intake valve or a broken valve spring.
    • Air leakage sounds at the exhaust system tailpipe that may indicate a worn or burnt exhaust valve or a broken valve spring.
    • Air leakage sounds from the crankcase, oil level indicator tube, or oil fill tube that 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 a damaged cylinder head gasket.
  7. Perform the leakage test on the remaining cylinders and record the values.
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