SEN04125-02 40 Troubleshooting
24 PC130-8
S-15 Abnormal noise is made 1
General causes why abnormal noise is made
q Abnormality due to defective parts
q Abnormal combustion
q 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 indi-
cate abnormality, however.
a When the engine is accelerated, it is operated in the
acceleration mode and its sound becomes a little larger
for up to about 3 seconds. This does not indicate abnor-
mality, however.
Causes
Leakage of air between turbocharger and cylinder head
Interference of turbocharger, seized turbocharger
Broken dynamic valve system (valve, rocker lever)
Defective inside of muffler (dividing board out of position)
Improper valve clearance
Excessive wear of piston ring, cylinder
Improper gear train backlash
Removed, seized bushing
Deformed cooling fan, loose fan belt, interference of fan belt
Clogged, seized injector
Dirt caught in injector
Improper fuel injection timing (abnormality in coolant
temperature sensor, boost temperature sensor)
Questions
Confirm recent repair history
Degree of use of machine Operated for long period E
Condition of abnormal noise
Gradually occurred QQ
Suddenly occurred QQ Q
Non-specified fuel is being used Q
Oil must be added more frequently w
Metal particles are found when oil filter is drained ww
Air leaks between turbocharger and cylinder head w
Check items
When engine is cranked, interference sound is generated around turbocharger w
When engine is cranked, abnormal sound is generated around cylinder head ww
When engine is cranked, beat noise is generated around muffler w
When exhaust manifold is touched immediately after starting engine, temperature of
some cylinders is low
wQ
Color of exhaust gas is
Blue under light load w
Black Qw Q
Engine does not pick up smoothly and combustion is irregular w
Abnormal noise is loud when engine is accelerated QQQQ
Blow-by gas is excessive w
Troubleshooting
When turbocharger is rotated by hand, it is found to be heavy q
Inspect dynamic valve system directly q
When muffler is removed, abnormal noise disappears q
Inspect valve clearance directly q
When compression pressure is measured, it is found to be low q
Inspect gear train directly qq
Inspect fan and fan belt directly q
When a cylinder is cut out for reduced cylinder mode operation, engine speed does
not change
qq
Abnormal noise is heard only when engine is started q
Confirm with monitoring function q
Remedy
Replace
Replace
Replace
Replace
Adjust
Replace
Replace
Replace
Correct
Replace
Replace
Replace
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