Cylinder Leakage Test

The combustion pressure leakage test provides an accurate means for determining engine condition. Combustion pressure leakage testing will detect exhaust and intake valve leaks (improper seating), leaks between adjacent cylinders or into water jacket, or any causes for combustion/compression pressure loss.

Check the coolant level and fill as required. Do not install the radiator cap. Start and operate the engine until it attains nor operating temperature, then turn the engine off. Remove the oil filler cap. Remove the air cleaner.

Calibrate the tester according to the manufacturer's instructions. The shop air source for testing should maintain 70 psi (483 kPa) minimum and 200 psi (1379 kPa) maximum. 80 psi (552 kPa) is recommended.

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.

1. Disconnect negative battery cable.
2. Remove engine cover from engine. Remove 4 ignition coils from the cylinder head cover. 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 Cylinder Head Leakdown Tester (J 35667), or equivalent.
NOTE: It may be necessary to hold the crankshaft balancer bolt to prevent the engine from rotating.
5. Apply shop air pressure to the leakdown tester 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 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 results.