Symptoms
  | Possible Causes
  | Remedy
  | 
Coolant leakage
  | 
|  •  | 
 From the thermostat gasket  |   
 | Check the mounting bolts
  | 
|  •  | 
 Check the torque of the mounting bolts  |   
 | 
|  •  | 
 Retighten the bolts and check leakage again.  |   
 | 
Check the gasket for damage
  | 
|  •  | 
 Check gasket or seal for damage  |   
 | 
|  •  | 
 Replace gaskets and reuse the thermostat.  |   
 | 
Cooled excessively
  | 
|  •  | 
 Low heater performance (cool air blowed-out)  |   
|  •  | 
 Thermogauge indicates 'LOW'  |   
 | Visually check after removing the radiator cap.
  | 
|  •  | 
 Insufficient coolant or leakage.  |   
 | 
|  •  | 
 After refilling coolant, recheck.  |   
 | 
GDS check & Starting engine
  | 
|  •  | 
 Check connection of the fan clutch or the fan motor.  |   
? If the fan clutch is always connected, there will be a noise at idle.
  | 
|  •  | 
 Check the engine coolant sensor, wiring and connectors.  |   
|  •  | 
 Replace the components.  |   
 | 
Remove the thermostat and inspect
  | 
|  •  | 
 Check if there are dusts or chips in the thermostat valve.  |   
|  •  | 
 Check adherence of the thermostat.  |   
 | 
|  •  | 
 Clean the thermostat valve and reuse the thermostat.  |   
|  •  | 
 Replace the thermostat, if it doesn't work properly.  |   
 | 
Heated excessively
  | 
|  •  | 
 Thermogauge indicates 'HI'  |   
 | Visually check after removing the radiator cap.
  | 
|  •  | 
 Insufficient coolant or leakage. 
? Be careful when removing a radiator cap of the overheated vehicle.  |   
|  •  | 
 Check air in cooling system.  |   
 | 
|  •  | 
 After refilling coolant, recheck.  |   
|  •  | 
 Check the cylinder head gaskets for damage and the tightening torque of the mounting bolts.  |   
 | 
GDS check & Starting engine
  | 
|  •  | 
 Check the fan motor performance as temperature varies.  |   
|  •  | 
 Check if the fan clutch slips.  |   
|  •  | 
 Check the water pump adherence or impeller damaged.  |   
 | 
|  •  | 
 Check the engine coolant sensor, wiring and connectors.  |   
|  •  | 
 Check the fan motor, the relay and the connector.  |   
|  •  | 
 Replace the fan clutch, if it doesn't work properly.  |   
|  •  | 
 Replace the water pump, if it doesn't work properly.  |   
 | 
Immerse the thermostat in boiling water and inspection.
  | 
|  •  | 
 After removing the thermostat, check it works properly. 
? Check the thermostat opens at the valve opening temperature.  |   
 | 
|  •  | 
 Replace the thermostat, if it doesn't work properly.  |   
 |