General
- The engine cooling system consists of a down-flow radiator which features high heat-dissipation performance, an electric-motor-driven fan, a water pump, a thermostat, and an engine coolant temperature sensor.
- The reservoir tank is designed to eliminate the need for replenishing coolant.
- The ECM controls the operation of the radiator main fan and sub fan depending on the signals from the engine coolant temperature sensor, vehicle speed sensor and A/C switch.
Cooling Circuits
The cooling system operates in three different phases depending on the temperature of the engine coolant.
Scheme 198
- 1st phase (thermostat closed) When the engine coolant temperature is below 76°C (169°F), the thermostat remains closed. The coolant flows through the bypass and heater circuits. This permits the engine to warm up quickly.
- 2nd phase (thermostat open) When the engine coolant temperature is above 76 - 80°C (169 - 176°F), the thermostat opens. The coolant flows through the radiator where it is cooled.
- 3rd phase (thermostat open and radiator fan operating) When the engine coolant temperature sensor sends a signal indicating a temperature above 91 °C (196°F) to the ECM, it causes the radiator fan (or fans) to operate.
Water Pump
The water pump is fitted in a housing formed in the rear chain cover using an O-ring as a seal between the pump case and the housing. The pump is driven by the timing chain through a sprocket and rotation of the impeller in a volute chamber creates flow of coolant toward the cylinder block.
The pump case is made of aluminum die casting and the impeller is made of steel sheet. The impeller shaft is supported by a ball bearing and a roller bearing. Its end exposed to coolant is sealed by a mechanical seal and the other end exposed to engine oil is sealed by an oil seal.
The volute chamber is formed by the rear chain cover and the upper oil pan. A metal gasket is used at the joint between the chain cover and upper oil pan.
Scheme 199
Mechanical Seal
The mechanical seal has its seat tightly fitted on the water pump shaft. Since it is a hermetic seal forming an integral part of the water pump, the water pump cannot be disassembled.
Scheme 200
Thermostat
The thermostat has a totally-enclosed wax pellet which expands as the coolant temperature increases. It opens and closes accurately at the preset temperatures and features high durability.
