6-28 Engine Mechanical - 3.8 L
Cylinder Leakage Test
Tools
Required
J 35667-A Cylinder Leakdown Tester
With the use of air pressure, 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.
Caution: Refer to Battery Disconnect Caution in
Cautions and Notices.
1. Remove the battery ground (negative) cable.
2. Remove the spark plugs. Refer to Ignition System.
3. Install the
J
35667-A.
4. Measure each cylinder on the compression
stroke, with both valves closed.
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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.
Important:
• Normal cylinder leakage is from 12 to 18 percent.
• Make a note of any cylinder with more leakage
than the other cylinders.
• Any cylinder with 30 percent leakage or more
requires service.
7. Inspect the four primary areas, to properly
diagnose a leaking cylinder.
Engine
8. If air is heard from the intake or exhaust system,
perform the following procedure:
• Remove the valve rocker arm cover of the
suspect cylinder head.
- Ensure that both valves are closed.
- Inspect the cylinder head for a broken valve
spring.
• Remove the suspect cylinder head and
inspect. Refer to Cylinder Head Clean
and Inspect.
9. If air is heard from the crankcase system at the
crankcase (oil filler tube), perform the following
procedure:
• Remove the piston from the suspect cylinder.
• Inspect the piston and connecting rod
assembly. Refer to Piston, Connecting Rod
and Bearings Clean/Inspect.
• Inspect the engine block. Refer to Engine
Block Clean and Inspect.
10. If bubbles are found in the radiator, perform the
following procedure:
• Remove both cylinder heads and inspect.
Refer to Cylinder Head Clean and Inspect.
• Inspect the engine block. Refer to Engine Block
Clean and Inspect.
11 . Remove the J 35667-A.
12. Install the spark plugs. Refer to Ignition System.
13. Install the battery ground (negative) cable. Refer to
Battery.
Drive Belt Diagnosis
Drive Belt Dressing
Important: Do not use drive belt dressing (adhesion
enhancement chemical) or any other chemicals on the
drive belt(s).
Drive Belt Noise
Drive belt noise may be described as a thumping
noise heard at, or just above idle speed, as a result of
drive belt pilling. In a single-belt drive, drive belt
pilling occurs when small particles of drive belt material
separate from the drive belt grooves, and form small
balls or pills in the drive belt grooves. While some drive
belt pilling is normal, excessive pilling can cause a
thump or knocking as the pills pass over various drive
belt pulleys. This causes the drive belt to repeatedly
jump off of and slap onto the drive belt pulley.
The thump or knocking noise easily misdiagnoses as
an engine noise. In order to diagnose drive belt
pilling, adhere to the following procedure:
·
1. Remove the drive belt.
2. Run the engine for no more
than 30 to 40 seconds, in order to confirm that the
engine noise disappears.
3. Inspect the power steering pulley for proper
alignment.
4. Inspect all other pulleys for excess paint, debris or
pills in the grooves.
5. Clean the pulleys with a wire brush, as necessary.
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