Abnormal Noise Is Made - Komatsu ecot3 PC300LC-8 Shop Manual

SEN02634-02
S-15 Abnormal noise is made
General causes why abnormal noise is made
• Abnormality due to defective parts
• Abnormal combustion
• Air sucked in from intake system
a
Judge if the noise is an internal noise or an external noise
before starting troubleshooting.
a
The engine is operated in the low-temperature mode while it is
not warmed up sufficiently. Accordingly, the engine sound
becomes a little larger. This does not indicate abnormality, how-
ever.
a
When the engine is accelerated, it is operated in the accelera-
tion mode and its sound becomes a little larger for up to about
3 seconds. This does not indicate abnormality, however.
Confirm recent repair history
Degree of use of
Operated for long period
machine
Gradually occurred
Condition of abnor-
mal noise
Suddenly occurred
Non-specified fuel is being used
Oil must be added more frequently
Metal particles are found when oil filter is drained
Air leaks between turbocharger and cylinder head
When engine is cranked, interference sound is generated around turbocharger
When engine is cranked, abnormal sound is generated around cylinder head
When engine is cranked, beat noise is generated around muffler
When exhaust manifold is touched immediately after starting engine, temperature of some cylin-
ders is low
Blue under light load
Color of exhaust
gas
Black
Engine does not pick up smoothly and combustion is irregular
Abnormal noise is loud when engine is accelerated
Blow-by gas is excessive
When turbocharger is rotated by hand, it is found to be heavy
Inspect dynamic valve system directly
When muffler is removed, abnormal noise disappears
Inspect valve clearance directly
When compression pressure is measured, it is found to be low
Inspect gear train directly
Inspect fan and fan belt directly
When a cylinder is cut out for reduced cylinder mode operation, engine speed does not change
Abnormal noise is heard only when engine is started
Check with monitoring function of the machine monitor.
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Remedy
40 Troubleshooting
1
Cause
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PC300, 350-8