Cylinder Leakage Test

Cylinder Leakage Test

Tools Required
J 35667-A Cylinder Head Leakdown Tester

Important: A cylinder leakage test will aid in the diagnosis. The cylinder leakage test may be used in conjunction with the engine compression test, to isolate the cause of leaking cylinders. 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 in Service Precautions.

1. Remove the battery ground - negative cable.

2. Remove the spark plugs.

3. Rotate crankshaft to place the piston in the cylinder being tested at Top Dead Center (TDC) of the compression stroke.

4. Install the J 35667-A.

Important: It may be necessary to hold the crankshaft balancer bolt, to prevent piston movement.

5. Apply air pressure, using the J 35667-A. Refer to the manufacturer's instructions.

6. Record the cylinder leakage readings for each cylinder. 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 values.