COOLANT FLOW
This cooling system operates in three steps, depending on temperature of the coolant that is flowing through the cooling circuit. (Scheme 14)
- Thermostat Closed - When coolant temperature is below 76°C (169°F), the thermostat remains closed and the coolant flows through the bypass and heater circuits.
- Thermostat Open - When coolant temperature is above 76-80°C (169-176°F), the thermostat opens and the coolant flows through the radiator where it is cooled.
- Electric Cooling Fan Operating - When coolant temperature rises above 95°C (203°F), the water temperature sensor is turned on and the radiator fan rotates.
Scheme 14
WATER PUMP
The water pump is located on the left front portion of the cylinder block and is driven by the timing belt. The thermostat is built into the engine coolant inlet which is located on the lower side of the water pump. When the impeller rotates, engine coolant is drawn into the water pump from the lower pipe via the thermostat (the lower pipe is connected to the radiator hose). It then flows along the perimeter of the impeller and is delivered to the engine's engine coolant passage. (Scheme 15)
Scheme 15
Mechanical Seal
The mechanical seal has its seat pressed into the water pump shaft to form the seal and water pump as a single unit. With this design, the water pump cannot be disassembled. (Scheme 16)
Scheme 16
Thermostat
The thermostat is powered to open the valve by a completely enclosed wax pellet. The wax pellet expands with increased temperature and provides the sure open-close operation of the valve, and it features high durability. (Scheme 17)
Scheme 17
ENGINE COOLANT TEMPERATURE SENSOR
The water temperature sensor is located on the water pipe. The water pipe is made of aluminum alloy. The sensor's thermistor changes resistance with respect to temperature. The thermostat signal converts into resistance then is transmitted to the ECU, which controls the fuel injection, ignition timing, etc. (Scheme 18)and (Scheme 19).
Scheme 18
Scheme 19
ELECTRONIC CONTROL UNIT (CONTROL SYSTEM)
The ECU receives signals from various sensors and switches, including the radiator fan control relay and the coolant temperature sensor. An input signal is sent from the coolant temperature sensor to the ECU. The ECU then analyzes the engine operating condition and sends an output signal to the radiator fan control relay to turn ON or OFF. Major items controlled by the ECU are as follows
- Fuel Injection Control
- Ignition System Control
- By-Pass Air Control
- EGR control
- Canister Purge Control
- Radiator Fan Control
- Engine Torque Control
- Air Conditioner Cut Control
- Self-Diagnosis Function
