Overheating Cause Analysis
Symptom Check items
Cooling
system parts
malfunctionPoor heat transferWater pump malfunction Worn or loose drive belt
Ð Thermostat stuck closed Ð
Damaged finsDust contamination or paper
clogging
Mechanical damage
Clogged radiator cooling tubeExcess foreign material (rust,
dirt, sand, etc.)
Reduced air flowCooling fan does not operate
ÐÐ Fan coupling does not operate
High resistance to fan rotation
Damaged fan blades
Damaged radiator shroud Ð Ð Ð
Improper coolant mixture ratio Ð Ð Ð
Poor coolant quality Ð Ð Ð
Insufficient coolantCoolant leaksCooling hoseLoose clamp
Cracked hose
Water pump Poor sealing
Radiator capLoose
Poor sealing
RadiatorO-ring for damage, deteriora-
tion or improper fitting
Cracked radiator tank
Cracked radiator core
Reservoir tank Cracked reservoir tank
Overflowing reservoir tankExhaust gas leaks into cooling
systemCylinder head deterioration
Cylinder head gasket deteriora-
tion
Except
cooling
system parts
malfunctionÐ Overload on engineAbusive drivingHigh engine rpm under no load
Driving in low gear for extended
time
Driving at extremely high speed
Powertrain system malfunction
Ð Installed improper size wheels
and tires
Dragging brakes
Improper ignition timing
Blocked or restricted air flowBlocked bumper Ð
Ð Blocked radiator grilleInstalled car brassiere
Mud contamination or paper
clogging
Blocked radiator Ð
Blocked condenser
Ð
Installed large fog lamp
ENGINE COOLING SYSTEM
LC-31
