Page COOLING SYSTEM - 8
Z001019/0_6_July 2008
SERVICE MANUAL MARINE ENGINES
05 COOLING SYSTEM
3
Closed Cooling Circuit
(internal)
3.1
At first, take into consideration the following possibilites:
-
Defective or faulty coolant temperature sensor.
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Coolant level in expansion tank < as minimum.
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Malfunction of thermostat
-
thermostat does not open or opens only partially
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thermostat blocked in partially open state
-
thermostat blocked in completely open state
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damaged thermostat sealing ring
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Malfunction of water circulating pump of engine
-
pump bearing defective
-
defective impeller seal
-
excessive wear of impeller wings
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Cooler cap (pressure loss)
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Cooler cap sealing defective
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vacuum valve defective
-
excess-pressure valve defective.
3.2
Malfunction of thermostat - overheating or slow heating of coolant:
-
Procedure
: Let the engine run until indicated temperature exceeds 80° C. Feel on hose of front
engine water pipe between heat exchanger and water-intake pipe.
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Result:
Hose cold.
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Conclusion: Thermostat got stuck in closed state.
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Result:
Hose warm or hot.
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Conclusion: Thermostat opens partially or completely.
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Procedure
: Let the engine run; temperature of coolant will rise very slowly (feel on hose of front
engine water pipe between heat exchanger and water-intake pipe).
-
Result:
Themperature on hose slowly rises simultaneously with temperature of coolant, but
does not reach operating temperature (80°C opening temperature of thermostat).
-
Conclusion: - Thermostat blocked in partially open or completely open state.
- Sealing ring of thermostat defective.
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Control:
- Thermostat got stuck in open or closed position.
- Defective thermostat sealing.
- Wrong thermostat for this type of engine.
ToC