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Cylinder Leakage Test: Procedure

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT: A leakage test may be performed in order to measure cylinder/combustion chamber leakage. High cylinder leakage may indicate one or more of the following:
  • Worn or burnt valves
  • Broken valve springs
  • Stuck valve lifters
  • Incorrect valve lash/adjustment
  • Damaged piston
  • Worn piston rings
  • Worn or scored cylinder bore
  • Damaged cylinder head gasket
  • Cracked or damaged cylinder head
  • Cracked or damaged engine block
    CAUTION: Refer to Battery Disconnect Caution .
  1. Disconnect the battery ground negative cable.
  2. Remove the spark plugs. Refer to Spark Plug Replacement .
  3. Rotate the crankshaft to place the piston in the cylinder being tested at top dead center (TDC) of the compression stroke.
  4. Thread the J 39313  into the spark plug hole. See Special Tools .
  5. Install the J 35667-A  or equivalent. See Special Tools .
    6. IMPORTANT: It may be necessary to hold the crankshaft balancer bolt to prevent the engine from rotating.
  6. Apply shop air pressure to the J 35667-A  and adjust according to the manufacturers instructions. See Special Tools .
  7. 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 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.
  8. Perform the leakage test on the remaining cylinders and record the values.
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