Engine Overheat
Problem / Symptom Cause Action
Instrument Shows High Tem-
perature
Clogged seawater inlet Clean
Low coolant level Fill with coolant / inspect for leaks
Clogged seawater filter (if equip-
ped)
Clean
Clogged hydraulic cooler See your authorized Yanmar dealer or
distributor
Seawater pump worn or dam-
aged
Defective sensor / instrument
Defective thermostat
Damaged closed coolant pump
Combustion gas leakage (cau-
ses loss of coolant)
Seawater pump belt slips or
pump pulley loose on pump shaft
Clogged heat exchanger
Engine Runs Cold
Problem / Symptom Cause Action
Instrument Shows Low Tem-
perature
Defective sensor / instrument See your authorized Yanmar dealer or
distributor
Defective thermostat
Cabin heater or boiler too large
Coolant Loss
Problem / Symptom Cause Action
Repeated Low Coolant Level Defective cylinder head gasket
(external leakage)
See your authorized Yanmar dealer or
distributor
External leakage at connection
Coolant Forced Out of Cool-
ant Recovery Tank
Turbocharging pressure enters
cooling system via leaking
charge air cooler
See your authorized Yanmar dealer or
distributor
Defective cylinder head gasket
(internal leakage)
White Smoke when Engine
Hot Indicates Water Vapor
Crack in cylinder head (not
cracks between valve seats)
See your authorized Yanmar dealer or
distributor
Cracked cylinder wall
Leaking cylinder head gasket
TROUBLESHOOTING
BY Series Operation Manual 63
© 2008 Yanmar Marine International
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