The cooling system includes: cooling jacket (in the cylinder block and in the cylinder head), radiator, water pump, thermostat, electric cooling fan, connecting hoses and other items. The coolant, heated in the cooling jacket, is pumped by a liquid pump into the radiator, where it is cooled by a 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.
The cooling jacket is a network of channels for the passage of fluid. These channels are formed by the spaces between the cylinder liners in the cylinder block and communicate with the channels in the block head. The movement of the liquid is organized in such a way as to provide the most efficient cooling of those elements of the engine that are most heated during its operation (in particular, the upper belt of engine cylinders and combustion chambers).
Radiator
The radiator is located in front of the car and is designed to cool the coolant coming from the cooling jacket. The radiator consists of a right and left tanks and a radiator core that connects the two tanks. In the upper tank there is an inlet pipe through which coolant flows from the cooling jacket, as well as a hose for bypassing excess coolant or steam. In the lower tank of the radiator there is a coolant outlet pipe through which it enters the coolant pump, as well as a drain cock through which the coolant is removed. The core of the radiator has many finned tubes through which the flow of coolant passes from the upper tank to the lower one, as well as cooling ribs for more efficient heat dissipation to the environment. 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. Automatic transmission models have a dedicated automatic transmission fluid cooler located in the lower radiator reservoir. The electrically driven fan is located behind the radiator, which facilitates airflow through the radiator. 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.
Radiator filler cap (radiator cap)
The radiator cap is a sealing type, it must seal the radiator and withstand the increased pressure resulting from the thermal expansion of the coolant. The increased pressure in the radiator prevents the coolant from boiling even at temperatures above 100°C. The radiator cap has steam (dropping) valve and air valve (vacuum valve). At a coolant temperature of 110-120°C, the excess pressure inside the radiator, caused by the thermal expansion of the liquid, reaches 0.3-1.0 kg/cm2 or 30-100 kPa. If the specified limit is exceeded, the steam valve opens under pressure and the steam is removed through the steam pipe. The air valve opens under the action of vacuum, which is formed inside the radiator after the engine is stopped and the temperature of the coolant drops. Opening this valve allows the coolant in the expansion tank to return to the cooling system.
Expansion tank
The expansion tank is designed to accumulate excess coolant volume, which is obtained as a result of its volumetric expansion when heated. When the coolant temperature drops, it returns from the expansion tank to the radiator. Thus, the radiator is always filled with coolant, and unnecessary loss of coolant is not allowed. To make sure it is necessary to top 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 wedge-shaped alternator drive belt.
Thermostat
The thermostat is installed on the inlet pipe of the cooling circuit. It has a wax bypass valve and an automatic valve controlled by the temperature of the coolant. The automatic valve closes when the coolant temperature drops and thereby prevents the circulation of fluid through the engine, speeding up the warm-up process. In this case, the bypass valve opens when the automatic valve is closed, then the coolant circulates only inside the engine (on a small circuit of the cooling system). When the coolant temperature rises, the automatic thermostat valve opens and the bypass valve (if it is installed) closes allowing coolant to circulate through the radiator. The wax filling inside the power element of the thermostat expands when heated and cools when cooled. Heating the wax filler of the power element creates a force that overcomes the force of the spring, under the action of which the valve is held closed, thus opening the automatic valve. As the wax filler cools, it shrinks. And under the action of the force of the spring, the automatic valve closes. In these engine models, the thermostat ensures that the operating temperature of the coolant is maintained at about 82°C.
Scheme of the cooling system of engines 3S-FE, 4S-FE
1 - from the radiator,
2 - inlet pipe,
3- thermostat,
4 - coolant pump,
5 - idle speed control valve,
6 - throttle body,
7 - from the heater,
8 - to the heater,
9 - outlet pipe,
10 - to the radiator,
11 - coolant bypass hose,
12 - oil cooler (if installed).