Komatsu BR380JG-1E0, Shop Manual, Page: 785 / 841

SEN02307-00 40 Troubleshooting
22
BR380JG-1E0
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 t
urbocharge
r and cylinder
head
Inter
feren
ce of t
urbocharg
er
, seized turb
ochar
ger
Bro
ken dynamic valve system (valve, r
ocker
lever)
Def
ective inside of muf
fler
(dividing boar
d out of po
sitio
n)
Impr
oper valve clearance
Excessive wear
of pist
o
n ring, cylind
er liner
Impr
oper ge
ar tr
ain ba
cklash
Remo
ved, seize
d bush
ing
Def
ormed cooling f
an, loo
se fan
belt,
inter
ference of fa
n belt
Clogged, seize
d
injector
Dirt caught
in injector
Impr
oper fu
el injection timing
(abnor
mality in coolant
low temper
ature
sensor
, boo
st temp
eratur
e sen
sor
)
Qu
estions
Confirm recent repair history
Degree of use of machine Operated for long period
E
Condition of abnormal
noise
Gradually occurred
Q Q
Sudden occurred
Q Q Q
Non-specified fuel is being used
Q
Oil must be added more frequently
w
Metal particles are found when oil filter is drained
w w
Air leaks between turbocharger and cylinder head
w
C
heck items
When engine is cranked, interference sound is generated around turbocharger
w
When engine is cranked, abnormal sound is generated around cylinder head
w w
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
w Q
Color of exhaust gas
Blue under light load
w
Black
Q w Q
Engine does not pick up smoothly and combustion is irregular
w
Abnormal noise is loud when engine is accelerated
Q Q Q Q
Blow-by gas is excessive
w
T
rouble
shooting
When turbocharger is rotated by hand, it is fount 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
q q
Inspect fan and fan belt directly
q
When a cylinder is cut out for reduced cylinder mode operation, engine speed does
not change
q q
Abnormal noise is heard only when engine is started
q
Confirm with INSITE or monitoring function on applicable machine side
q
Remedy
Re
place
Re
place
Co
rrec
t
Re
place
Adjust Re
place
Re
place
Re
place
Co
rrec
t
Re
place
Re
place
Re
place