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| Illustration 1 | g01448575 |
Cooling system (1) Shunt tank for radiator (2) Bypass (3) Water regulator housing (4) Radiator cores (5) Turbocharger (6) Turbocharger oil lines (7) Transmission oil cooler (8) Rear axle oil cooler (9) Engine oil cooler (10) Water pump (11) Inlet tube (radiator) (AA) Unregulated coolant (BB) Regulated coolant | |
Water pump (10) draws coolant directly from radiator (4). The coolant is pumped through engine oil cooler (9). The oil then flows through rear axle oil cooler (8) and transmission oil cooler (7). From the transmission oil cooler, coolant flows through the engine block.
The coolant flows around the cylinder liners, through the water directors, and into the cylinder heads. The water directors send the flow of coolant around the exhaust valves and the passages for exhaust gases in the cylinder heads. The coolant then goes to the front of the cylinder heads and into water regulator housing (3). When the coolant is inside of housing (3), two water temperature regulators control the direction of coolant flow within housing (3) .
When the coolant temperature is below 81 °C (178 °F), water temperature regulator (3) will be closed. The path for the coolant return to radiator (4) is blocked. The coolant flows through regulator housing (3). Then, the coolant is fed back to the inlet of water pump (10) .
As the coolant temperature reaches 82° ± 1°C (180° ± 2°F), water temperature regulator (3) starts to open. Coolant begins to flow to tube (11). When the coolant temperature reaches 92 °C (198 °F), the coolant is at normal operating temperature. Water temperature regulator (3) is fully open and the flow of coolant to bypass (2) is blocked. The path for the coolant to radiator (4) through tube (11) is open. The temperature of the returned coolant will be reduced as the coolant flows through radiator (4) .
Note: Water temperature regulator (3) is an important part of the cooling system. Water temperature regulator (3) divides the coolant flow between radiator (4) and bypass (2) in order to maintain normal operating temperature. If the water temperature regulator is not installed in the system, the flow of coolant is not regulated. Most of the coolant will go through the bypass (2) and bypass radiator assembly (4). The engine, the transmission, and the hydraulic oil may overheat during high ambient temperatures.
Coolant for the Turbocharger
Turbocharger (5) has one inlet and one outlet. Turbocharger oil lines (6) are connected to the turbocharger at these ports. Pressurized engine oil flows from the crankcase of the engine into turbocharger (5) through turbocharger oil lines (6). This engine oil is used for lubrication of the bearings in the turbocharger and for cooling the turbocharger. The oil then drains through turbocharger oil lines (6) into the oil pan on the bottom of the engine.
Radiator Assembly
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| Illustration 2 | g01449270 |
Radiator assembly (front view) (12) Aftercooler (13) Hydraulic oil cooler for the steering system (14) Hydraulic oil cooler (15) Refrigerant condenser (16) Fuel cooler | |
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| Illustration 3 | g01449322 |
Radiator cores (front view) (4) Radiator cores (17) Radiator bottom tank | |
The radiator assembly is the source of coolant for the cooling system. The radiator is made up of radiator cores (4) and radiator bottom tank (17). Also, the radiator assembly includes two air aftercoolers (12), two hydraulic oil coolers (14), one hydraulic oil cooler for the steering system (13), refrigerant condenser (15), and fuel cooler (16) .
ReferenceFor additional information about the refrigerant condenser, refer to the Service Manual module Systems Operation, SENR5664, "Air Conditioning and Heating R-134a for All Caterpillar Products".
ReferenceFor more information about cooling the hydraulic system, refer to the Service Manual module Systems Operation, "Hydraulic Fan System" for the machine that is being serviced.
Radiator bottom tank (17) is divided into two sections. Coolant flows from water temperature regulator (3) into the rear section of the bottom tank.
The radiator is made up of fourteen cores. Each core contains three tubes in the rear and three tubes in the front. The rear tubes and the front tubes are connected by a crossover tank at the top of each core. As the coolant flows into the rear section of the bottom tank, the coolant is pushed up the rear tubes of each core. As the coolant reaches the top of the cores, the coolant flows through the crossover tank. Then, the coolant flows through the front tubes into the front section of the bottom tank.
As the coolant flows through the radiator cores in both directions and the air is pulled around the radiator cores, the temperature of the coolant is reduced.
Transmission Oil Cooler and Rear Axle Oil Cooler
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| Illustration 4 | g01449541 |
Left side of engine (7) Transmission oil cooler (8) Rear axle oil cooler (9) Engine oil cooler (10) Water pump (18) Bonnet (19) Inlet for axle oil cooler (20) Outlet for transmission oil cooler (21) Inlet for transmission oil cooler (22) Outlet for axle oil cooler (23) Bonnet | |
Engine coolant from water pump (10) flows through engine oil cooler (9). Coolant flows from the engine oil cooler (9) into bonnet (23). Bonnet (23) directs the flow of coolant into rear axle oil cooler (8). The coolant flows through long tubes inside the oil cooler to bonnet (18). Coolant flows through bonnet (18) and into transmission oil cooler (7). Coolant flows through long tubes inside the transmission oil cooler to bonnet (23). The coolant then flows through bonnet (23) and into the engine cylinder block.
High temperature transmission oil flows from the torque converter outlet to transmission oil cooler (7). This oil flows through inlet (21) to the inside of the oil cooler. As the oil flows through the inside of the cooler, heat is transferred from the oil to the coolant that is flowing through the tubes. The cooled oil flows out of the cooler through outlet (20). The oil then flows through a line in order to lubricate the planetary group.
High temperature oil from the rear axle is pumped to rear axle oil cooler (8). This oil flows through inlet (19) to the inside of the oil cooler. As the oil flows through the inside of the cooler, heat is transferred from the oil to the coolant that is flowing through the tubes. The cooled oil flows out of the cooler through outlet (22). The oil then flows back to the rear axle.
Front Axle Oil Cooler
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| Illustration 5 | g01449758 |
Front axle oil cooler (right side view) (24) Front axle oil cooler (25) Pump and motor | |
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| Illustration 6 | g01449765 |
Front axle oil cooler cores (bottom view) (26) Outlet for axle oil (27) Inlet for axle oil | |
Front axle oil cooler (24) is mounted inside the loader frame above the front axle. Pilot hydraulic oil drives a hydraulic motor which turns pump (25) for the front axle oil cooler. The pilot oil then flows into the top rear port of the cooler core assembly. The pilot oil flows through long tubes inside each core. When the oil reaches the bonnet at the front of the assembly, the oil flows through the outlet on the top of the bonnet. The pilot oil returns to the main hydraulic tank.
Pump (25) sends axle oil from the front axle to inlet (27). The axle oil flows through the cooler core on the left side of the assembly. As the axle oil flows through the cores, heat from the axle oil is transferred to the pilot oil that is flowing through the tubes. When the oil reaches the front of the core, the oil passes through a tube into the cooler core on the right side of the assembly. At the rear of the right cooler core, the cooled oil passes through outlet (26) and flows to the front axle.
Air-to-Air Aftercooler
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| Illustration 7 | g01449371 |
Air-to-air aftercooler (left side view) (5) Turbocharger (12) Aftercooler core (28) Air cleaner (29) Muffler (30) Air intake manifold (CC) Inlet air (DD) Exhaust gases | |
Note: The left side muffler has been removed for clarity in Illustration 7.
The air-to-air aftercooler system provides cooled air to air intake manifold (30) on top of the engine. Air is drawn in through air cleaners (28) and into the compressor side of turbocharger (5). The air is compressed by the turbocharger. This causes a rise in the temperature of the air. The air is sent through the tube into aftercooler core (12). The air is cooled in the aftercooler core. From core (12), the air flows into air intake manifold (30) on the top of the engine. The air flow 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 port within 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 and 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 the turbocharger (5). 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 (5) pass through the exhaust outlet, through a muffler (29), and through an exhaust stack.
The efficiency of the engine will increase due to the cooler inlet air. This helps to provide lowered fuel consumption, increased horsepower output, and improved emissions.
ReferenceFor additional information about the turbocharger, refer to the Service Manual module Systems Operation/Testing and Adjusting, "Air Inlet and Exhaust System" for the engine that is being serviced.