Komatsu ecot3 PC300-8, Shop Manual

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40 Troubleshooting SEN02634-02
PC300, 350-8
21
S-14 Coolant temperature becomes too high (overheating) 1
General causes why coolant temperature becomes too high
• Lack of cooling air (deformation, damage of fan)
• Drop in heat dissipation efficiency
• Problem in coolant circulation system
Cause
Brok
en c
y
linder hea
d,
head gas
ket
Holes caused by pit
ti
n
g
Clogged,
broke
n oil c
ool
er
Lack of
coolant
Brok
en wat
e
r
pump
Def
e
c
tive
operat
ion of
t
h
erm
o
st
at
Clogged,
crus
hed
radi
a
tor f
ins
Clogged r
a
di
at
or
core
Def
e
c
tive
radiat
or c
a
p (p
ressur
e
va
lv
e)
S
lipping
fan
belt,
worn f
a
n pulley
Def
ec
tive coolant
t
e
mper
at
ure gauge
Rise
o
f oi
l t
e
m
p
erat
ure
in hydrau
lic pum
p
sy
st
em
Q
uest
ions
Confirm recent repair history
Degree of use of
machine
Operated for long period
E E E E
Condition of
overheating
Sudden overheated
Q w Q
Always tends to overheat
Q w w Q
Coolant tempera-
ture gauge
(if installed) Rises quickly
Q w
Does not go down from red range
w
Radiator coolant level monitor indicates drop of coolant level (if monitor is installed)
w
Engine oil level has risen and oil is milky
w Q
Fan belt tension is low
w
Check
it
em
s
When fan belt is turned, it has play
w
Milky oil is floating on coolant
w
There are excessive air bubbles in radiator, coolant spurts back
w
When light bulb is held behind radiator core, no light passes through
w
Radiator shroud, inside of underguard are clogged with dirt or mud
w w
Coolant is leaking because of cracks in hose or loose clamps
w
Coolant flows out from radiator overflow hose
w
Fan belt whines under sudden acceleration
w
Hydraulic oil temperature gauge indicates red range faster than engine coolant tem-
perature gauge does (if they are installed)
w
T
roubleshoot
ing
When compression pressure is measured, it is found to be low
q
Car
ry out
t
rou
bl
es
hoot
ing
in H-m
ode.
Inspect cylinder liner directly
q
Inspect oil cooler directly
q
Temperature difference between upper and lower tanks of radiator is large
q
When operation test of thermostat is carried out, it does not open at cracking tem-
perature
q
Temperature difference between upper and lower tanks of radiator is slight
q
Inspect radiator core directly
q
When operation of radiator cap is carried out, its cracking pressure is low
q
Inspect fan belt, pulley directly
q
When coolant temperature is measured, it is fount to be normal
q
Remedy
Replace Replace Replace Add Replace Replace Correct Correct Replace Correct Replace
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