STEYR MOTORS Marine Engine 2012 Series, Service Manual

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Cooling System
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05.00.03 Error detection cooling system
1. Ask for the following information:
- Model and serial number of engine?
- Engine operating hours? (wear and corrosion)
- How long does the problem already exist? (gradual or sudden occurrence)
- Operating conditions prior to occurrence of problem
- What repair- or service works have already been carried out (thermostat,
etc.)?
- At what engine speed does the problem occur?
- At what engine load does the problem occur?
2. Closed Cooling Circuit (internal)
2.1 At first, take into consideration the following possibilities:
- Defective or faulty coolant temperature sensor.
- Coolant level in expansion tank less than minimum.
- Malfunction of thermostat
- thermostat does not open or opens only partially
- thermostat blocked in partially open state
- thermostat blocked in completely open state
- damaged thermostat sealing ring
- Malfunction of coolant circulation pump
- pump roller bearing defective
- defective seal
- case pump wheel
- Pressure cap
- pressure cap sealing defective (loss of system pressure)
- vacuum valve defective
- excess-pressure valve defective
- opening pressure of cap according to specification
2.2 Malfunction of thermostat - overheating or slow heat build up in coolant system:
- Procedure : Let the engine run until indicated temperature exceeds 80° C.
Feel temperature in coolant outlet pipe to radiator
- Result: Hose cold.
- Conclusion: Thermostat got stuck in closed state.
- Result:
Hose warm or hot.
- Conclusion: Thermostat opens partially or completely.
- Procedure : Let the engine run; temperature of coolant will rise very slowly
Feel temperature in coolant outlet pipe to radiator