Tools Required

J 35667-A  Cylinder Head Leakdown Tester

Fig 1: View Of Leakdown Tester
Courtesy of GENERAL MOTORS CORP.
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 or burnt valves
• Broken valve springs
• Stuck valve lash adjuster
• 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 spark plugs. Refer to Spark Plug Replacement in Engine Control.
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-A  .
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 throttle control module or air inlet hose may indicate a worn or burnt intake valve or a broken valve spring.
   • Air leakage sounds at the exhaust system tailpipe 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 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.