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Isuzu 20LE - Abnormal Noise Due to Hydraulic Lash Adjustor; Troubleshooting Procedure

Isuzu 20LE
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ENGINE DIAGNOSIS (C22NE, 22LE, 20LE) 6-9
Abnormal Noise Due to Hydraulic Lash Adjuster
Should abnormal noise due to the hydraulic lash
adjuster trouble be heard immediately after the engine
is started, inspect as follows:
Condition Possible cause Correction
Abnormal noise is heard Air contaminated Bleed
HLA is spongy Check ball valve broken Repair
Safety valve in cylinder head
broken
Replace
Valve clearance is not zero HLA inside stick Replace HLA assembly
Troubleshooting Procedure
Short out each spark plug in sequence using insulated
spark plug wire removers. Locate cylinder with
defective bearing by listening for abnormal noise that
stops when spark plug is shorted out.
Condition Possible cause Correction
Noise from connecting rods or
from connecting rod bearings
(Faulty connecting rods or
connecting rod bearings usually
make an abnormal noise slightly
higher than the crank bearing
noise, which becomes more
evident when engine is
accelerated)
Bearing or crankshaft pin worn Replace connecting rod bearings
and crankshaft or regrind
crankshaft and install the under
size bearing
Crankpin out of round Replace connecting rod bearings
and crankshaft or regrind
crankshaft and install the under
size bearing
Connecting rod bent Correct or replace
Connecting rod bearing seized Replace connecting rod bearings
and crankshaft or regrind
crankshaft and install the under
size bearing
Troubleshooting Procedure
Abnormal noise stops when the spark plug on the
cylinder with defective parts is shorted out.
Condition Possible cause Correction
Piston and cylinder
(Faulty piston or cylinder usually
makes a combined mechanical
thumping noise which increases
when engine is suddenly
accelerated but diminishes
gradually as the engine warms up)
Piston clearance increased due to
cylinder wear
Replace piston and cylinder body
Piston seized Replace piston and cylinder body
Piston ring broken Replace piston and cylinder body
Piston defective Replace pistons and others

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