980M and 982M Wheel Loaders Power Train, Steering, Braking, Hydraulic, and Machine Systems Caterpillar

Illustration 1	g03658782
Cooling system (1) Water regulator (2) Radiator (3) Water pump (4) Axle oil cooler (5) Bypass (6) Engine oil cooler (AA) Regulated coolant (BB) Unrestricted coolant

Water pump (3) draws coolant directly from the radiator (2). Coolant is pumped through engine oil cooler (6) and axle oil coolers (4). Then, the coolant flows into the engine block. 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, the water regulator controls the direction of coolant flow within the housing.

When the coolant temperature is below 81 °C (178 °F), the water regulator will be closed. The path for the coolant return to radiator (2) is blocked. The coolant flows through the bypass (5) and back to the water pump (3).

As the coolant temperature reaches 83° ± 1°C (181° ± 2°F), the water temperature regulator starts to open. Coolant begins to flow to radiator (2). When the coolant temperature reaches 92 °C (198 °F), the coolant is at normal operating temperature. The water temperature regulator is fully open and the flow of coolant to bypass (5) is blocked. The path for coolant to radiator (2) is open. The temperature of the returned coolant will be reduced as the coolant flows through radiator (2).

Note: The water temperature regulator is an important part of the cooling system. The water temperature regulator divides the coolant flow between radiator (2) and bypass (5). 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 the radiator (2). The engine, the transmission, and the hydraulic oil may overheat during high ambient temperatures.

Radiator Assembly

Illustration 2	g03658862
Radiator (Rear View) (7) Hydraulic Oil Cooler

Radiator assembly (2) 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 (2) includes the air aftercooler and the hydraulic oil cooler (7).

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.

Axle Oil Cooler

Illustration 3	g03659012
(8) Axle oil cooler pump (9) Electromagnetic clutch (10) Relay (11) Serpentine belt (12) Heat exchangers (13) Hydraulic lines to rear axle (14) Rear axle differential (15) Hydraulic lines to front axle (16) Front axle differential

The axle oil cooler system consists of the following components: Axle oil cooler pump (8), electromagnetic clutch (9), relay (10), heat exchangers (12) and hydraulic lines (13, 15).

The axle oil cooler system circulates the axle oil through a heat exchanger and sends the axle oil back to the axle differentials. The heat exchanger uses cooled hydraulic oil to cool the axle oil. The axle oil cooler pump (1) and electromagnetic clutch (2) are located on the engine. The pump is driven by the serpentine belt (11). The temperature sensors (not shown) located in the axle differentials monitor the temperature and report to the transmission ECM. When the transmission ECM recognizes an oil temperature of 75° C (167° F), the transmission ECM sends a current to energize the relay (10). The transmission ECM uses a logic that either axle will turn on the cooler once the temperature threshold is crossed. The transmission ECM does not wait for both axles to be above the threshold. When the relay is energized, current is directed to the electromagnetic clutch (9). With the electromagnetic clutch engaged, the axle oil cooler pump (8) draws the warm oil out of the front and rear axle differential (14, 16). The axle flow from the pump is directed through the hoses into the heat exchangers (12). From the exchangers, the axle oil flows to the front differential (16) and to the rear differential (14). If the axle oil temperature drops to 68° C (154° F), the transmission ECM will de-energize the relay (10).

Air to Air Aftercooler

Illustration 4	g03659142
Air to Air Aftercooler (17) Aftercooler (18) Turbocharger (19) Cooled air enters the air intake manifold on the right side of the machine. (CC) Inlet air

Illustration 5	g03659157
Air to Air Aftercooler (18) Turbocharger (20) Air cleaner (21) Diesel particulate filter (22) SCR canister (CC) Inlet air (DD) Exhaust gases

The air-to-air aftercooler system (ATAAC system) provides cooled air to air intake manifold (19) on the right side of the machine. Air is drawn in through air cleaner (20) and into turbocharger (18). The air is sent through the tube into aftercooler core (17). From core (17), the air flows into the air intake manifold (19) on the right side of the machine. 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 manifold is pulled into the cylinder. The inlet valves close when the piston begins to move up on the compression stroke. Air is compressed and 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 (18). 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 (18) pass through the exhaust outlet, through a diesel particulate filter (21), and through the exhaust stack.

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