Leakage test cylinder (A20NFT/LHU)
|
|
Leakage test cylinder (A20NFT/LHU)
|
Special tools
EN-35667-A
Test instrument for leakage from cylinder head
For equivalent regional tools, see Special tools
|
Note
|
|
A leakage test can be carried out to check for any leakage adjacent to the cylinder/combustion chamber. Significant leakage may indicate one of the following problems:
|
|
•
|
Incorrectly adjusted valve clearance
|
|
•
|
Worn or scratched cylinder bore
|
|
•
|
Damaged cylinder head gasket
|
|
•
|
Cracked or damaged cylinder head
|
|
•
|
Cracked or damaged engine block
|
|
1.
|
Warning
|
|
Unless the instructions specify otherwise, the ignition and the ignition switch be in the OFF or LOCK position and all electrical consumers OFF before servicing is performed on an electrical component. Remove the battery's negative cable to prevent sparking if any tool or equipment comes in contact with an exposed electrical connection. If these safety precautions are not followed, it may result in personal injury and/or damage to the vehicle and its components.
|
|
For cars equipped with OnStar® (UE1) and backup battery:
|
|
The backup battery is an extra power source that makes it possible to use certain functions in OnStar® even if the power supply from the car battery to VCIM (OnStar® module) is cut. Do not disconnect the car battery or remove the OnStar® fuse if the ignition key is in any position other than OFF. RAP power supply (Retained Accessory Power) should time out or be deactivated (if the driver's door opens the RAP power supply is deactivated) before the power is disconnected. If the power supply to the OnStar® module is disengaged in any other way while the ignition is switched on or while the RAP function is activated then this can activate the OnStar BUB® system (backup battery), causing the battery to be discharged and causing permanent damage. When the backup battery has been activated, it continues to be connected until it is completely discharged. The backup battery cannot be recharged and once it has been activated it must be replaced.
|
|
|
|
|
|
Disconnect the battery's ground cable.
|
|
2.
|
Remove the spark plugs. See Replacing the spark plugs.
|
|
3.
|
Rotate the crankshaft so that the piston in the cylinder to be tested is at top dead centre (TDC).
|
|
4.
|
Fit
test instrument
EN-35667-A or equivalent.
|
|
5.
|
|
Note
|
|
It may be necessary to secure the bolt for the crankshaft balance weight to prevent the crankshaft rotating.
|
Connect compressed air to the
test instrument
EN-35667-A and adjust in accordance with the manufacturer's instructions.
|
|
6.
|
Record the value for cylinder leakage. A cylinder leakage in excess of 25 percent is considered to be large and may require action. If a large leakage exists, check the following:
|
|
|
•
|
Noise from air leakage at the throttle spigot or inlet hose which may indicate worn or burned intake valve or a broken valve spring.
|
|
|
•
|
Noise from air leakage at the exhaust system tail pipe which may indicate worn or burned exhaust valve or a broken valve spring.
|
|
|
•
|
Noise from air leakage from the crankcase, the oil level indicator tube and oil filler tube, which may indicate worn piston rings, a damaged piston, a worn or scratched cylinder bore, a damaged engine block or a damaged cylinder head.
|
|
|
•
|
Air bubbles in the cooling system which may indicate a damaged cylinder head or a damaged gasket for the cylinder head.
|
|
7.
|
Carry out a leakage test on the remaining cylinders and record the values.
|
