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| Illustration 1 | g02712857 |
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Cooling system (1) Water regulator. (2) Aftercooler. (3) Radiator. (4) Cooler for power train (Torque converter and transmission). (5) Water pump. (6) Engine oil cooler. (7) Bypass. (AA) Regulated coolant. (BB) Unrestricted coolant. | |
Water pump (5) draws coolant from the cooler for power train (4). Coolant flows from pump (5) into the engine block. Coolant flows over engine oil cooler (6). Coolant flows around the cylinder liners, through the water directors and into the cylinder head. The water directors send the flow of coolant around the valves and the passages for exhaust gases in the cylinder head. The coolant then goes to the front of the cylinder head and into water regulator housing (1). When the coolant is inside the housing, water regulator (1) controls the direction of coolant flow within the housing.
When the coolant temperature is below
As the coolant temperature reaches
Note: Water temperature regulator (1) is an important part of the cooling system. Water temperature regulator (1) divides the coolant flow between radiator (3) and bypass (7). Normal operating temperature is maintained. If the water temperature regulator is not installed in the system, the flow of coolant is not regulated. Most of the coolant will bypass radiator (3). The engine, the transmission, and the hydraulic oil may overheat during high ambient temperatures.
Reference: For more information on the coolant flow, refer to Systems Operation, KENR9241, "C7.1 Engines for Caterpillar Built Machines", "Cooling System".
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| Illustration 2 | g06155079 |
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(1) Water lines from radiator
(2) Hydraulic return line (3) Front axle oil cooler line set (4) Solenoid valve (5) Front axle temperature sensor (6) Axle oil cooler pump (7) Axle oil cooler (8) Rear axle oil cooler line set (9) Rear axle temperature sensor | |
The axle oil cooler is a water over oil heat exchanger system. Rear axle oil temperature sensor (9) and front axle oil temperature sensor (5) send signals to the transmission ECM. When the signal is at or above the trigger point for axle cooling to be activated, the ECM sends a signal to solenoid valve (4). Solenoid valve (4) opens and allows oil from the implement system to flow to the motor portion of axle oil cooling pump (6). Axle oil cooler pump (6) pumps axle oil from the axles through front cooler line set (3) and rear cooling line set (8). Axle oil flows to axle oil cooler (7). Water from the engine cooling system flows through axle oil cooler (7) and removes heat from the axle oil. Axle oil cooling pump (6) sends the oil back to the axles through line sets (3) and (8). The hydraulic oil returns to the hydraulic oil tank through return line (2). The axle oil cooling system is a closed loop system axle oil and hydraulic oil do not mix. The axles are also closed loop and oil from the front axle and rear axle do not mix.
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| Illustration 3 | g02712863 |
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Radiator (Rear View) (8) Hydraulic Oil Cooler | |
Radiator assembly (3) is the source of coolant for the cooling system. The radiator is made up of the following three sections: radiator top tank, radiator bottom tank, and radiator core assemblies. Also, radiator assembly (3) includes air aftercooler (2) and hydraulic oil cooler (8).
Reference: For additional information about cooling the hydraulic system, refer to the Service Manual module Systems Operation, "Hydraulic Fan System" for the machine that is being serviced.
The radiator top tank accepts the return coolant from the water regulator housing. The coolant flows from the radiator top tank down the tubes of the radiator core. Then, the coolant flows into the bottom tank. As the coolant flows through the radiator core and the air is pulled around the radiator core, the temperature of the coolant is reduced.
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| Illustration 4 | g02712865 |
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Air to Air Aftercooler (right side view) (2) Aftercooler (9) Cooled air enters the air intake manifold on right side of machine (10) Turbocharger (CC) Inlet air (DD) Exhaust gases | |
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| Illustration 5 | g02712867 |
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Air to Air Aftercooler (left side view) (2) Aftercooler (10) Turbocharger (11) Air cleaner (12) Diesel particulate filter (CC) Inlet air (DD) Exhaust gases | |
The air-to-air aftercooler system (ATAAC system) provides cooled air to air intake manifold (9) on the right side of the machine. Air is drawn in through air cleaner (11) and into turbocharger (10). The air is sent through the tube into aftercooler core (2). From core (2), the air flows into air intake manifold (9) on the right side of the machine. The flow of air from the inlet port into the cylinders is controlled by inlet valves. Each cylinder has inlet valves and exhaust valves in the cylinder head. The inlet valves open when the piston moves downward on the inlet stroke. When the inlet valves open, cooled compressed air from the inlet manifold is pulled into the cylinder. The inlet valves close when the piston begins to move up on the compression stroke. The air in the cylinder is compressed. The fuel is injected into the cylinder when the piston is near the top of the compression stroke. Combustion begins when the fuel mixes with the air. The force of combustion pushes the piston downward on the power stroke. The exhaust valves open and the exhaust gases are pushed through the exhaust port.
Exhaust gases from the exhaust manifold flow into the turbine side of turbocharger (9). The high-pressure exhaust gases cause the turbocharger turbine wheel to rotate. The turbine wheel is connected to the shaft that drives the compressor wheel. Exhaust gases from turbocharger (9) pass through the exhaust outlet, through diesel particulate filter (12), and through the exhaust stack.
The efficiency of the engine will increase due to the cooler inlet air. The cooler air helps to provide lowered fuel consumption and increased horsepower output.