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There are a few possible causes for the problem :
1. Cooling fan. The cooling fan operates at different speed for cooling and if it is not working at the highest speed when the temperature is high, the efficiency is insufficient. However this would not be a likely cause as at cruising speed the moving air should be able to cool the radiator to lower the temperature reading.
2. Radiator partially clogged. If the radiator is clooged partially, cooling efficiency would be reduced causing high temperature reading. When this occurs, the higher the speed the higher would the be temperature reading.
3. Bad thermostat. It could be stuck in partially open position resulting in reduced coolant movement that would cause the temperature to rise.
4. Insufficient coolant. When engine is cold, remove the radiator cap and check if the coolant level is at the neck. Check the reserve tank coolant level.
5. Bad water pump. This would reduce the coolant flow efficiancy.
From the above, item 2 and 3 would be the most probable cause.
Friday, June 26th, 2009 AT 10:49 AM