Closed liquid cooling system with forced circulation of liquid

The tightness of the cooling system allows the engine to operate at a coolant temperature exceeding 100º C, but when the coolant overheat indicator lights up (above 105º C), the engine must be stopped and the cause of the overheating eliminated.

ZMZ-402 and UMZ-4215 engine cooling system: 1 - with one heater; II - with two heaters and an electric pump (for vans with two rows of seats and buses); 1 - expansion tank; 2 - thermostat; 3 - coolant temperature indicator sensor; 4 - radiator; 5 - radiator drain plug (tap); 6 - fan; 7 - fan drive belt; 8 - coolant pump drive belt; 9 - coolant pump; 10 - drain valve of the cylinder block; 12 - electric pump of the heating system; 11.13 - heater tap; 14 - additional heater radiator; 15, 16 - main heater radiator; 17 - main thermostat valve; 18 - bypass valve; A - the thermostat is closed; C - thermostat open

The cooling system consists of an engine cooling jacket, radiator, water pump, thermostat, expansion tank and connecting hoses and tubes.

The heater radiator is also connected to the cooling system.

The pressure in the system is created by a water pump, which is driven by a belt from the crankshaft.

From the pump, liquid is supplied to the engine cooling jacket. From the jacket, liquid flows into the thermostat.

Depending on the temperature of the liquid, it then passes into the water pump (at low temperatures) or into the radiator (at high temperatures), from where, after cooling, it enters the water pump.

On vehicles with a ZMZ-4062 engine, an electric fan is installed, mounted on the fan casing, which in turn is mounted on the radiator.

On cars with ZMZ-402 or ZMZ-4021 engines, the fan is driven by a belt from the engine crankshaft.

The cooling system is filled with Tosol-A40M coolant.

It is not recommended to fill the cooling system with water, since the antifreeze contains anti-corrosion and anti-foaming additives, as well as additives that prevent scale deposits.

The coolant level in the expansion tank on a cold engine should be at or above the MIN mark by 20-40 mm.

If necessary, add coolant to the expansion tank. In case of frequent topping up, check the tightness of the system.

If there is a significant leak of liquid, water may be used to restore the level in exceptional cases.

In this case, the density of the mixture will inevitably decrease and its freezing temperature will increase. Therefore, the mixture should be replaced with fresh coolant as soon as possible.