Cylinder Leakage Test
Special Tools
| • |
EN-35667-A
Leakdown Tester |
| • |
EN-35667-8
Adapter, Cylinder Leakdown Tester |
Fro equivalent regional tools, refer to
Special Tools .
|
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 |
| • |
Damaged valve
train components |
| • |
Worn or scored
cylinder bore |
| • |
Damaged cylinder
head gasket |
| • |
Cracked or damaged
cylinder head |
| • |
Cracked or damaged
engine block |
| 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. |
|
Note: It may be
necessary to hold the crankshaft balancer bolt to prevent the
engine from rotating.
|
| 4. |
Install 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 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. |
|
