D439E Service Manual 2. Engine Mechanical System (D439E)
30
Diagnosis
Symptom Possible cause Maintenance
Compression
pressure is
excessively low
Cylinder head Gasket is melt
Piston ring is worn or damaged Piston
or cylinder is damaged
Valve seat worn or damaged
Replace gasket (check the status of
head surface, block head)
Replace the ring
Repair or replace piston or cylinder
block
Repair or replace valve or seat ring
Oil pressure is
excessively low
Engine oil depleted
Oil pressure switch fail
Oil filter clogged
Oil pump gear or case is worn Engine
oil viscosity is low
Oil relief valve stuck (open) Excessive
bearing clearance
Add engine oil
Replace oil pressure switch Replace
the filter with new one Replace the gear
or case
Replace engine oil
Repair valve
Replace the bearing
Oil pressure is
excessively noise
Oil relief valve stuck (close) Repair the relief valve
Connecting rod noise
or main bearing noise
Improper oil supply
Low oil pressure
Low engine oil viscosity
Excessive bearing clearance
Check the engine oil level
Refer to ‘oil pressure is excessively
low’
Replace engine oil
Replace the bearing
Excessive engine
vibration
Engine mounting bolt is loose
Transmission mounting bolt is loose
Cross member bolt is loose
Engine mounting rubber is damaged
Transmission mounting rubber is
damaged
Retighten
Retighten
Retighten
Replace
Replace
Engine coolant level
is low
Engine coolant leak
Radiator core Joint is damaged
Radiator and heater hose corroded and
cracked
Radiator cap valve or spring setting is
defective
Thermostat defect
Water pump defect
Replace
Radiator is clogged
Foreign substance intrusion into engine
coolant
Replace
Engine coolant
temperature is
abnormally high
Thermostat in defective
Radiator cap is defective
Cooling system flow is defective Drive
belt is loose
Water pump is defective Temperature
wiring is defective Radiator fan is
defective
Engine coolant is low
Replace
Replace
Replace
Adjust or Replace
Replace
Repair or replace
Repair or replace
Add coolant
Engine coolant
temperature is
abnormally low
Thermostat is defective Temperature
wiring is defective
Replace
Repair or replace
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