Engine Overheat; Engine Runs Cold; Coolant Loss - Yanmar 4BY2 Operation Manuals

Engine Overheat

Problem / Symptom
Instrument Shows High Tem-
perature

Engine Runs Cold

Problem / Symptom
Instrument Shows Low Tem-
perature

Coolant Loss

Problem / Symptom
Repeated Low Coolant Level
Coolant Forced Out of Cool-
ant Recovery Tank
White Smoke when Engine
Hot Indicates Water Vapor
BY Series Operation Manual
Cause
Clogged seawater inlet
Low coolant level
Clogged seawater filter (if equip-
ped)
Clogged hydraulic cooler
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
Cause
Defective sensor / instrument
Defective thermostat
Cabin heater or boiler too large
Cause
Defective cylinder head gasket
(external leakage)
External leakage at connection
Turbocharging pressure enters
cooling system via leaking
charge air cooler
Defective cylinder head gasket
(internal leakage)
Crack in cylinder head (not
cracks between valve seats)
Cracked cylinder wall
Leaking cylinder head gasket
© 2008 Yanmar Marine International
TROUBLESHOOTING
Action
Clean
Fill with coolant / inspect for leaks
Clean
See your authorized Yanmar dealer or
distributor
Action
See your authorized Yanmar dealer or
distributor
Action
See your authorized Yanmar dealer or
distributor
See your authorized Yanmar dealer or
distributor
See your authorized Yanmar dealer or
distributor
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