4 cylinders + 6 cylinders 4 cylinders + 6 cylinders - Steyr Motors

ToC
05 COOLING SYSTEM
SERVICE MANUAL MARINE ENGINES
3 Closed Cooling Circuit (internal)
3.1 At first, take into consideration the following possibilites:
- Defective or faulty coolant temperature sensor.
- Coolant level in expansion tank < as 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 water circulating pump of engine
- pump bearing defective
- defective impeller seal
- excessive wear of impeller wings
- Cooler cap (pressure loss)
- Cooler cap sealing defective
- 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.
- 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 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.
- Control: - Thermostat got stuck in open or closed position.
- Defective thermostat sealing.
- Wrong thermostat for this type of engine.
Page COOLING SYSTEM - 8 Z001019/0_6_July 2008