The cooling system is designed to ensure optimal thermal operation of the engine
The engine cooling system is liquid, closed type, with forced circulation of coolant.
The main units and components of the cooling system include: radiator, fan with a viscous drive coupling, fan casing, fan shell, water channel housing, water pump, thermostats, channels and connecting pipelines for the passage of coolant.
The diagram of the cooling system with a fan coaxial to the crankshaft and with a viscous coupling of the fan drive is shown in Figure 1.
During the operation of the engine, the circulation of coolant in the system is created by a water pump 8.
The coolant from the pump 8 is pumped into the cooling cavity of the left row of cylinders through channel 9 and through channel 14 into the cooling cavity of the right row of cylinders.
Washing the outer surfaces of the cylinder liners, the coolant enters the cooling cavities of the cylinder heads through the holes in the upper sealing planes of the cylinder block.
From the cylinder heads, the heated liquid flows through channels 4, 5 and 6 into the water box of the housing of the water channels 17, from which, depending on the temperature, it is directed to the radiator or to the pump inlet.
Part of the liquid is discharged through the channel 15 to the oil heat exchanger 16, where heat is transferred from the oil to the coolant.
From the heat exchanger, the coolant is directed to the water jacket of the cylinder block in the area of the fourth cylinder.
The thermal mode of the engine is adjusted automatically:
- two thermostats that control the direction of fluid flow depending on the temperature of the coolant at the outlet of the engine. The nominal temperature of the coolant at the engine outlet should be within 85-90 ° C.
- a viscous coupling of the fan drive, depending on the air temperature at the outlet of the radiator ONV.
The body of the water channels (Figure 1) is cast from cast iron alloy and bolted to the front end of the cylinder block.
In the body of the water channels, the inlet 7 and outlet 11 cavities of the water pump, connecting channels 5 and 12, channels 9 and 14 supplying coolant to the cylinder block, channels 4 and 6 removing coolant from the cylinder heads, bypass channel 13, outlet channel 15 to the oil heat exchanger, cavities of the water box 17 for installing thermostats, channel 10 supplying coolant to the water pump from the radiator are cast.
The water pump (Figure 2) is of centrifugal type, mounted on the housing of the water channels.
A radial double-row ball-roller bearing with a roller 6 is pressed into the housing 1. On both sides, the ends of the bearing are protected by rubber seals. The bearing is lubricated by the manufacturer.
Replenishment of lubricant in operation is not required. The thrust ring 8 prevents the movement of the outer bearing cage in the axial direction. The impeller 3 and the pulley 7 are pressed onto the ends of the bearing roller.
The oil seal 2 is pressed into the pump housing, and its sliding ring is constantly pressed by a spring to the sliding ring 5, which is inserted into the impeller through a rubber cuff 4.
There are two holes in the pump housing between the bearing and the oil seal: lower and upper. The upper hole is used to ventilate the cavity between the bearing and the oil seal, and the lower one is used to control the serviceability of the mechanical seal.
The leakage of liquid from the lower hole indicates a malfunction of the seal.
In operation, both holes must be clean, as their blockage will lead to the failure of the bearing.
The oil seal of the water pump (Figure 3) consists of a brass outer casing 1, into which a rubber cuff 2 is inserted.
Inside the cuff there is a spring 3 with internal 4 and external 5 frames. The spring preloads the sliding ring 6.
The slip ring is made of graphite-lead solid-pressed antifriction material.
The fan and coupling are viscous (Figure 4).
The nine-blade fan 1 with a diameter of 710 mm is made of glass-filled polyamide, the fan hub 3 is metal.
To drive the fan, an automatically switched-on viscous coupling 2 is used, which is attached to the fan hub 3.
The principle of operation of the coupling is based on the viscous friction of the fluid in small gaps between the driven and driving parts of the coupling. A silicone liquid with high viscosity is used as the working fluid.
The coupling is not disassembled and does not require maintenance in operation.
The coupling is switched on 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 fixed annular shell rigidly attached to the engine.
The fan casing, the fan shell contribute to an increase in the flow rate of air pumped by the fan through the radiator.
The fan casing and the fan shell are connected by a U-shaped annular rubber seal.
The radiator (of KAMAZ cars) is copper-soldered, to increase heat transfer, cooling tapes are made with louvered openings, attached by side brackets through rubber cushions to the frame spars, and the upper thrust to the unifying air collector.
Thermostats (Figure 5) allow you to accelerate the heating of a cold engine and maintain the temperature of the coolant at least 75 ° C by changing its flow through the radiator.
In the water box 5 of the water channel housing, two thermostats with an opening temperature of (80+2) °C are installed in parallel.
When the coolant temperature is below 80 ° C, the main valve 12 is pressed against the seat of the housing 14 by a spring 11 and blocks the passage of coolant into the radiator.
The bypass valve 6 is open and connects the water box of the body of the water channels through the bypass channel 4 to the inlet of the water pump.
At a coolant temperature above 80 ° C, the filler 9 in the cylinder 10 begins to melt, increasing in volume. The filler consists of a mixture of 60% ceresine (petroleum wax) and 40% aluminum powder.
The pressure from the expanding filler is transmitted through the rubber insert 8 to the piston 13, which, being squeezed out, moves the cylinder 10 with the main valve 12, compressing the spring 11.
An annular passage for coolant into the radiator opens between the housing 14 and the valve 12.
At a coolant temperature of 93 ° C, the thermostat is fully opened, the valve rises to a height of at least 8.5 mm.
Simultaneously with the opening of the main valve, the bypass valve 6 moves along with the cylinder, which closes the hole in the water box of the water channel housing connecting it to the inlet of the water pump.
When the coolant temperature drops to 80 ° C and below, the valves 12 and 6 return to their original position under the action of springs 7 and 11.
To control the temperature of the coolant, two temperature sensors 1 and 2 are installed on the water box of the water channel housing.
Sensor 1 provides readings of the current temperature value to the instrument panel, sensor 2 serves as a coolant overheating alarm.
When the temperature rises to 98 - 104 ° C, the warning lamp for emergency overheating of the coolant lights up on the instrument panel.
The expansion tank 1 (Figure 1) is installed on the engine of KAMAZ vehicles on the right side along the course of the car.
The expansion tank is connected by a bypass pipe 19 to the inlet cavity of the water pump 13, by a steam drain tube 2 to the upper radiator tank and to the liquid discharge tube from the compressor 3.
The expansion tank serves to compensate for the change in the volume of the coolant when it expands from heating, and also allows you to control the degree of filling of the cooling system and helps to remove air and steam from it.
The expansion tank is made of a translucent propylene copolymer.
A plug of the expansion tank is screwed onto the neck of the tank (Figure 6) with inlet valves 6 (air) and exhaust (steam).
The exhaust and intake valves are combined into a valve block 8. The valve block is non-removable.
The exhaust valve loaded with a spring 3 maintains an overpressure of 65 kPa (0.65 kgf / cm2) in the cooling system, the intake valve 6 loaded with a weaker spring 5 prevents the creation of a vacuum in the system when the engine cools down.
The intake valve opens and communicates the cooling system with the environment when the discharge in the cooling system is 1-13 kPa (0.01-0.13 kgf/ cm2).
The engine is refueled with coolant through the filler neck of the expansion tank.
Before filling the cooling system, you must first open the tap of the heating system.
To drain the coolant, open the drain valves of the heat exchanger and the pump unit of the preheater, unscrew the plugs on the lower radiator tank and expansion tank.
It is not allowed to open the plug of the expansion tank on a hot engine, as this may cause the release of hot coolant and steam from the neck of the expansion tank.
The operation of the vehicle without an expansion tank plug is not allowed.
Tension adjustment (Figure 7) of the belt of the polyclinic 2 drive of the generator and water pump for engines with the fan located along the axis of the crankshaft is performed as follows:
- loosen the bolt 11 for fixing the generator"s rear paw, the nut 10 for fixing the generator"s front paw, the bolt 8 for fixing the generator bar, the bolt 5 for fixing the tension bolt;
- by moving the nut 6 to provide the necessary belt tension; nut 7 to fix the position of the generator;
- tighten bolts 5, 8 and 11, tighten nut 10.
After adjustment, check the tension:
- a properly stretched belt 2, when pressed into the middle of the largest branch with a force of 44.1 ± 5 N (4.5 ± 0.5 kgf), should have a deflection of 6-10 mm.