950H Wheel Loader, 962H Wheel Loader and IT62H Integrated Toolcarrier Braking and Hydraulic Fan System Caterpillar

Illustration 1	g01172446
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 78 °C (172 °F), water regulator (1) will be closed. The path for the coolant return to radiator (3) is blocked. The coolant flows through bypass (7) and back to water pump (5).

As the coolant temperature reaches 80° ± 2°C (176° ± 4°F), water temperature regulator (1) starts to open. Coolant begins to flow to radiator (3). When the coolant temperature reaches 94 °C (201 °F), the coolant is at normal operating temperature. Water temperature regulator (1) is fully open and the flow of coolant to bypass (7) is blocked. The path for coolant to radiator (3) is open. The temperature of the returned coolant will be reduced as the coolant flows through radiator (3).

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.

Radiator Assembly

Illustration 2	g01172483
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.

Air to Air Aftercooler

Illustration 3	g01172495
Air to Air Aftercooler (2) Aftercooler. (9) Muffler. (10) Air cleaner. (11) Turbocharger. (12) Cooled air enters the air intake manifold on right side of machine. (CC) Inlet air. (DD) Exhaust gases.

The air-to-air aftercooler system (ATAAC system) provides cooled air to air intake manifold (12) on the right side of the machine. Air is drawn in through air cleaner (10) and into turbocharger (11). The air is sent through the tube into aftercooler core (2). From core (2), the air flows into air intake manifold (12) 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 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 turbocharger (11). 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 (11) pass through the exhaust outlet, through muffler (9), and through the exhaust stack.

The efficiency of the engine will increase due to the cooler inlet air. This helps to provide lowered fuel consumption and increased horsepower output.