The cooling system includes: cooling jacket (in the cylinder block and in the cylinder head), radiator, water pump, thermostat and electric cooling fan.
The coolant, heated in the cooling jacket, is pumped into the radiator by a pump, where it is cooled by the air flow created by the fan and the oncoming air flow that occurs when the vehicle is moving. The coolant then returns to the cooling jacket by means of a pump and cools the engine.
Pic. 2.193. 1MZ-FE engine cooling system and a schematic diagram of the system operation: 1 - coolant pump; 2 - outlet branch pipe of the cooling system; 3 - bypass channel; 4 - intake manifold; 5 - thermostat; 6 – block of cylinders; 7 - radiator
Radiator of the cooling system
The radiator is located in front of the car and is designed to cool the liquid. The coolant, heated when passing through the cooling jacket, is cooled in the radiator by the air flow sucked in by the electric fan, as well as by the oncoming air flow that occurs when the vehicle is moving. Models with automatic transmission have a special automatic transmission fluid cooler, which is located in the lower radiator tank. Behind the radiator is an electrically driven fan. The fan turns on only if the coolant temperature reaches the operating value. This reduces the power consumption of the fan drive and prevents motor overcooling.
Expansion tank of the cooling system
The expansion tank is designed to accumulate excess coolant volume, which is obtained as a result of its expansion when heated. When the coolant temperature drops, the coolant returns from the expansion tank to the radiator. Before topping up the coolant, it is necessary to check its level in the expansion tank.
Coolant pump
The coolant pump provides forced circulation of the coolant through the cooling system. It is installed in front of the cylinder block and is driven from the crankshaft by a timing belt.
Thermostat
The thermostat is installed on the inlet pipe of the cooling circuit. It regulates the circulation of the coolant. When the coolant temperature is less than 80–84°C, the thermostat valve is closed and the coolant circulates through the small circuit of the cooling system (without passing through the radiator), which speeds up the engine warm-up process. When the coolant temperature rises, the thermostat valve opens, allowing the coolant to circulate through the large cooling system circuit (through the radiator). In these engine models, the thermostat begins to open at a coolant temperature of 80-84°C and opens fully at a temperature of about 95°C.