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Cylinder Leakage Test

Cylinder Leakage Test



Special Tools

• EN-35667-A Leakdown Tester

• EN-35667-8 Adapter, Cylinder Leakdown Tester



Warning

Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

For Vehicles equipped with OnStar® (UE1) with Back Up Battery:

The Back Up Battery is a redundant power supply to allow limited OnStar® functionality in the event of a main vehicle battery power disruption to the VCIM (OnStar®module). Do not disconnect the main vehicle battery or remove the OnStar® fuse with the ignition key in any position other than OFF. Retained accessory power (RAP) should be allowed to time out or be disabled (simply opening the driver door should disable RAP) before disconnecting power. Disconnecting power to the OnStar® module in any way while the ignition is On or with RAP activated may cause activation of the OnStar® Back-Up Battery (BUB) system and will discharge and permanently damage the back-up battery. Once the Back-Up Battery is activated it will stay on until it has completely discharged. The BUB is not rechargeable and once activated the BUB must be replaced.


Note

A leakage test may be performed to measure cylinder/combustion chamber leakage. High cylinder leakage may indicate one or more of the following:

• Worn, burnt, or stuck valves

• Broken valve springs

• Incorrect valve lash

• Damaged valve train components

• 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. Refer to Battery Negative Cable Disconnection and Connection .

2. Remove the glow plugs.

3. Rotate the crankshaft to place the piston in the cylinder being tested at top dead center (TDC) of the compression stroke.

4.
Note

It may be necessary to hold the crankshaft balancer bolt to prevent the engine from rotating.


Install the EN-35667-8 adapter and EN-35667-A tester.

5. Apply shop air pressure to EN-35667-A 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 intake manifold tube, may indicate a worn, stuck or burnt intake valve, broken valve spring, incorrect valve lash or damaged valve train components.

• Air leakage sounds at the exhaust system tailpipe may indicate a worn, burnt, or stuck exhaust valve, broken valve spring, incorrect valve lash or damaged valve train components.

• 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 gasket.

7. Perform the leakage test on the remaining cylinders and record the values.