The cooling system is liquid, closed, with forced circulation, it consists of a water jacket in the engine block and cylinder head, a coolant pump, a radiator, an expansion tank, a fan, a thermostat, an expansion tank plug, a fan casing, a drain cock and a plug.

The cooling system circuit includes radiator 5 of the cabin heater, and for buses and GAZ-2705 Kombi, in addition, radiator 4 of the additional heater and electric pump 3.

Engine Cooling Schematic

The car has a tap 2 for the electric heater radiator.

In one housing there is a faucet connected through a mechanical gearbox by a microelectric motor, turned on by handle 1.

The faucet has two positions - fully open or completely closed, until the handle is turned 90 ° to the right of the initial position, the faucet is closed, when the handle is further turned to the right until it stops, the faucet is open.

A tee 7 is located in the drain branch of the heater radiator at its highest point. The tee is located in the cab under the instrument panel on the right side.

In the position of plug 8 of the tee turned out by 2-3 turns, the heating system communicates with the atmosphere, which makes it possible to completely eliminate air pockets when the engine cooling system and heating system are filled with working fluid.

Maintaining the correct engine temperature is critical to engine wear and fuel economy.

The optimum temperature of the coolant (85-90°C) is maintained by an automatic thermostat and a cover on the radiator lining.

To control the temperature of the coolant, there is a temperature gauge, the sensor of which is screwed into the thermostat pipe located on the cylinder head.

In addition, there is an indicator on the instrument panel that lights up red when the liquid temperature rises above 105 ° C.

The warning sensor is located in the rear cover of the cylinder head.

If the indicator lights up, the cause of overheating should be immediately identified and eliminated.

Thermostat operation

Thermostat with a solid filler, two valves, type TC-107-01 is located in the outlet pipe of the cylinder head and is connected by hoses to coolant pump and radiator.

The main thermostat valve starts to open at a coolant temperature of 78-82°C. At a temperature of 94°C, it is already fully open.

When the main valve is closed, the liquid in the engine cooling system circulates, bypassing the radiator, through the open additional thermostat valve inside the engine cooling jacket.

When the main valve is fully open, the secondary valve is closed and all the liquid passes through the cooling radiator.

The body heater is connected in parallel with the radiator and the thermostat does not disconnect it from the engine.

Therefore, when the engine is warming up, do not open the air intake damper and turn on the heater motor.

The thermostat automatically maintains the required temperature of the coolant in the engine, turning off and on the circulation of the liquid through the radiator.

In cold weather, especially at low engine loads, almost all heat is removed by blowing cold air into the engine, and the coolant does not circulate through the radiator.

In order to maintain the optimal temperature regime of the engine at negative ambient temperatures, it is necessary to cover the radiator lining with a cover.

Never remove the thermostat.

In the cold season, an engine without a thermostat warms up for a long time and operates at a low coolant temperature.

As a result, its wear accelerates, fuel consumption increases, tarry substances are abundantly deposited in the engine, and normal air temperature in the car cabin is not ensured.

In the warm season, in the absence of a thermostat, most of the coolant will circulate in a small circle (through the engine cooling jacket), bypassing the radiator. As a result, this will lead to overheating of the engine.

Coolant PumpAccessory Drive Belts

Coolant pump - centrifugal type. The pump bearing is separated from the coolant by a non-separable self-locking stuffing box.

The liquid leaking through the stuffing box does not enter the bearing, but flows out through the control hole 3, which must be periodically cleaned.

The pump bearing is kept from moving by retainer 1, which is screwed up to the stop and centered.

The bearing is filled with grease during assembly and no relubrication is required during operation.

The coolant pump pulley is driven along with the alternator pulley by a single V-belt from the crankshaft pulley.

Fan — six-blade, plastic.

It is driven from the crankshaft by a V-belt. The fan rotates in two bearings.

The bearings are installed in a special bracket fixed on the cover of the timing gears with three pins.

ZMZ-402 cooling system radiator

Radiator - tubular-tape, with side plastic tanks.

The tanks are connected to the core of the radiator through a rubber seal by crimping the base plate along the flange of the plastic tanks.

On the tanks and the upper plate of the radiator core there are brackets for attaching the radiator to the car body.

On the right tank (in the direction of the car) in the lower part there is a drain plug for draining the coolant.

Expansion tank—plastic, connected by a hose to a branch pipe supplying cooled liquid from the radiator to the engine, and a tube to the branch pipe thermostat and left radiator tank.

There is a MIN mark on the reservoir - the lower permissible level of coolant in the reservoir. The expansion tank is closed with a screw plug that maintains increased pressure in the cooling system.

The plug of the expansion tank, which hermetically closes the cooling system, has two valves: a steam valve that opens at a pressure of 80-110 kPa (0.8-1.1 kgf / cm2), and an air valve that opens at a rarefaction of 10-10 kPa (0.01-0.1 kgf/cm2).