Cylinder Combustion Pressure Leakage

A leakage test may be performed in order to measure cylinder/combustion chamber leakage. High leakage may indicate a 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/damaged cylinder head, or cracked/damaged engine block.

1. Disconnect battery negative battery cable. Remove spark plugs.
2. Rotate crankshaft to place the piston in the cylinder being tested at Top Dead Center (TDC) of the compression stroke. Install Cylinder Head Leakdown Tester (J-35667-A). Apply shop air pressure to tester and adjust according tester manufacturer's instructions.
3. Record 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 throttle body or air inlet hose that may indicate a worn or burnt intake valve or a broken valve spring.
   • Air leakage sounds at tailpipe that may indicate a worn or burnt exhaust valve or broken valve spring.
   • Air leakage sounds from crankcase, oil level indicator tube or oil fill tube that may indicate worn piston rings, damaged piston, worn or scored cylinder bore, damaged engine block or damaged cylinder head.
   • Air bubbles in cooling system may indicate a damaged cylinder head or damaged cylinder head gasket.
4. Perform leakage test on remaining cylinders and record the values.