The cooling system is intended to ensure the optimal thermal operating conditions of the engine.
The engine cooling system is of the liquid, closed type, with forced circulation of the coolant.
The main units and assemblies of the cooling system include: the radiator, the fan with a viscous drive coupling, the fan shroud, the fan cowl, the water channel housing, the water pump, the thermostats, and the channels and connecting pipelines for the passage of the coolant.
The diagram of the cooling system with a fan coaxial with the crankshaft and with a viscous fan drive coupling is shown in Figure 1.
During engine operation, the circulation of the coolant in the system is created by the water pump 8.
The coolant is delivered from the pump 8 into the cooling cavity of the left-hand row of cylinders through channel 9 and through channel 14 — into the cooling cavity of the right-hand row of cylinders.
Washing the outer surfaces of the cylinder liners, the coolant passes through the holes in the upper mating surfaces of the cylinder block into the cooling cavities of the cylinder heads.
From the cylinder heads, the heated coolant passes along channels 4, 5 and 6 into the water box of the water channel housing 17, from which, depending on the temperature, it is directed to the radiator or to the pump inlet.
Part of the coolant is diverted along channel 15 into the oil heat exchanger 16, where heat is transferred from the oil to the coolant.
From the heat exchanger, the coolant is directed into the water jacket of the cylinder block in the area of the fourth cylinder.
The thermal operating conditions of the engine are regulated automatically:
- by two thermostats, which control the direction of the coolant flow depending on the coolant temperature at the engine outlet. The rated coolant temperature at the engine outlet must be within the range of 85–90 °C;
- by the viscous fan drive coupling, depending on the air temperature at the radiator outlet.
The water channel housing (Figure 1) is cast from cast iron alloy and secured by bolts to the front end face of the cylinder block.
In the water channel housing, the inlet cavity 7 and the outlet cavity 11 of the water pump, the connecting channels 5 and 12, the channels 9 and 14 supplying the coolant to the cylinder block, the channels 4 and 6 diverting the coolant from the cylinder heads, the bypass channel 13, the channel 15 diverting to the oil heat exchanger, the cavities of the water box 17 for installing the thermostats, and the channel 10 supplying the coolant to the water pump from the radiator are cast.
The water pump (Figure 2) is of the centrifugal type, installed on the water channel housing.
Into the housing 1, a radial double-row ball-and-roller bearing with shaft 6 is pressed. On both sides, the end faces of the bearing are protected by rubber seals. The grease has been placed in the bearing by the manufacturer.
Replenishment of the grease during operation is not required.
The thrust ring 8 prevents the displacement of the outer race of the bearing in the axial direction. On the ends of the bearing shaft, the impeller 3 and the pulley 7 are press-fitted.
The oil seal 2 is pressed into the pump housing, and its sliding ring is constantly pressed by a spring against the sliding ring 5, which is inserted into the impeller through the rubber collar 4.
In the pump housing, between the bearing and the oil seal, two holes are provided: the lower and the upper.
The upper hole serves for ventilation of the cavity between the bearing and the oil seal, and the lower one — for checking the serviceability of the face seal.
A leak of coolant from the lower hole indicates a fault in the seal.
During operation, both holes must be clean, since their blockage will lead to failure of the bearing.
The water pump oil seal (Figure 3) consists of a brass outer housing 1, into which a rubber collar 2 is inserted.
Inside the collar, a spring 3 with an inner frame 4 and an outer frame 5 is arranged. The spring presses the sliding ring 6.
The sliding ring is made of a graphite-lead hard-pressed antifriction material.
Fan and viscous coupling (Figure 4).
The nine-blade fan 1 with a diameter of 710 mm is made of glass-filled polyamide; the fan hub 3 is made of metal.
For the fan drive, an automatically engaging viscous-type coupling 2 is used, which is fastened to the fan hub 3.
The operating principle of the coupling is based on the viscous friction of the fluid in the small clearances between the driven and the driving parts of the coupling. A high-viscosity silicone fluid is used as the working fluid.
The coupling is non-detachable and requires no maintenance during operation.
The coupling engages when the air temperature at the radiator outlet rises to 61–67 °C.
The thermobimetallic spiral 4 controls the operation of the coupling.
The fan is placed in a stationary annular cowl rigidly attached to the engine.
The fan shroud and the fan cowl contribute to increasing the flow rate of the air forced by the fan through the radiator.
The fan shroud and the fan cowl are connected by an annular rubber seal of U-shaped cross-section.
The radiator (of KAMAZ vehicles) is copper-brazed; to increase heat transfer, the cooling bands are made with louvre-punched slots; it is fastened by side brackets through rubber cushions to the frame side members, and by an upper tie rod to the combining air manifold.
The thermostats (Figure 5) allow accelerating the warming-up of a cold engine and maintaining the coolant temperature not lower than 75 °C by changing its flow rate through the radiator.
In the water box 5 of the water channel housing, two thermostats are installed in parallel with an initial opening temperature of (80 + 2) °C.
At a coolant temperature below 80 °C, the main valve 12 is pressed against the seat of the body 14 by the spring 11 and closes the passage of the coolant to the radiator.
The bypass valve 6 is open and connects the water box of the water channel housing along the bypass channel 4 to the water pump inlet.
At a coolant temperature above 80 °C, the filler 9 located in the bulb 10 begins to melt, increasing in volume.
The filler consists of a mixture of 60 % ceresin (petroleum wax) and 40 % aluminium powder.
The pressure from the expanding filler is transmitted through the rubber insert 8 to the piston 13, which, being forced outwards, displaces the bulb 10 with the main valve 12, compressing the spring 11.
Between the body 14 and the valve 12, an annular passage for the coolant to the radiator opens.
At a coolant temperature of 93 °C, the thermostat opens fully; the valve rises to a height of not less than 8.5 mm.
Simultaneously with the opening of the main valve, the bypass valve 6 moves together with the bulb, closing the hole in the water box of the water channel housing that connects it to the water pump inlet.
When the coolant temperature drops to 80 °C and below, under the action of the springs 7 and 11, the valves 12 and 6 return to their initial position.
To monitor the coolant temperature, two temperature sensors 1 and 2 are installed on the water box of the water channel housing.
Sensor 1 provides the readings of the current temperature value to the instrument panel; sensor 2 serves as a coolant overheating warning device.
When the temperature rises to 98–104 °C, the critical coolant overheating warning lamp lights up on the instrument panel.
The expansion tank 1 (Figure 1) is installed on the engine of KAMAZ vehicles on the right-hand side in the direction of travel of the vehicle.
The expansion tank is connected by the bypass pipe 19 to the inlet cavity of the water pump, by the steam vent tube 2 to the upper radiator tank and to the coolant outlet tube from the compressor 3.
The expansion tank serves to compensate for the change in the volume of the coolant during its expansion due to heating, and also allows monitoring the degree of filling of the cooling system and promotes the removal of air and steam from it.
The expansion tank is made of semi-transparent propylene copolymer.
Onto the neck of the tank, the expansion tank cap (Figure 6) is screwed with the valves: inlet 6 (air) and outlet (steam).
The outlet and inlet valves are combined into a valve block 8. The valve block is non-detachable.
The outlet valve, loaded by the spring 3, maintains an excess pressure in the cooling system of 65 kPa (0.65 kgf/cm²); the inlet valve 6, loaded by a weaker spring 5, prevents the creation of a vacuum in the system when the engine cools down.
The inlet valve opens and connects the cooling system to the environment when the vacuum in the cooling system is 1–13 kPa (0.01–0.13 kgf/cm²).
The engine is filled with coolant through the filler neck of the expansion tank.
Before filling the cooling system, the heater system cock must first be opened.
To drain the coolant, the drain cocks of the heat exchanger and of the pump unit of the pre-start heater must be opened, and the plugs on the lower radiator tank and on the expansion tank must be unscrewed.
It is not permitted to open the expansion tank cap on a hot engine, since hot coolant and steam may be ejected from the neck of the expansion tank.
Operation of the vehicle without the expansion tank cap is not permitted.
Adjust the tension (Figure 7) of the poly-V belt 2 of the alternator and water pump drive for engines with the fan arranged on the crankshaft axis as follows:
- slacken the bolt 11 fastening the rear foot of the alternator, the nut 10 fastening the front foot of the alternator, the bolt 8 fastening the alternator plate, the bolt 5 fastening the tensioning bolt;
- by moving the nut 6, ensure the necessary belt tension; with the nut 7, fix the position of the alternator;
- tighten the bolts 5, 8 and 11, tighten the nut 10.
After adjustment, check the tension:
- a correctly tensioned belt 2, when pressed at the middle of the longest run with a force of 44.1 ± 5 N (4.5 ± 0.5 kgf), must have a deflection of 6–10 mm.
