Small and large circle of coolant circulation
In order for the engine to warm up to operating temperature faster, the cooling system is divided into a small and a large circle of coolant circulation.
- After starting a cold engine, the coolant circulates in a small circle: from the coolant pump to the engine housing, and also to the cylinder head and back to the coolant pump. In the small circle, the coolant also passes through the heating heat exchanger.
- When the coolant reaches the required temperature, the radiator turns on during the cooling process.
- The thermostat turns on the radiator. It opens the connecting hose between the engine and the radiator in such a way that the cold coolant from the radiator mixes with the already heated coolant from the small circle.
- As a result of the gradual mixing of hot and cold coolant, a sharp temperature drop in the engine housing is avoided. The cold water flowing down pushes the hot coolant up into the radiator. There it is cooled by means of radiator plates. Simultaneously with the inclusion of the radiator, the small circle of circulation is closed.
- The functions of the switch in the thermostat are carried out by a special solid thermosensitive filler, which is located between the walls of the glass, in which the valve plate is fixed. When the coolant is heated, the temperature-sensitive filler melts and expands, thereby opening the valve.
The principle of operation of the thermostat
- As the temperature of the coolant rises, the thermostat opens more and more the passage for cold coolant from the radiator and at the same time closes the small circle of circulation.
- If, while driving, the coolant temperature drops below operating temperature, the spring in the thermostat presses on the valve plate, returns it to its original position and blocks access to the radiator until the coolant heats up again. The thermostat is located when looking in the direction of travel:
- On a 1.4 liter engine (engine type «WITH») in front of the coolant pump in the upper radiator hose;
- On 1.7-/1.8-liter and 16-valve engines below the ignition distributor;
- On a diesel engine, below the brake booster vacuum pump.