ENGINE COOLING SYSTEM.
The engine cooling system is a closed loop system;
engine coolant is contained and recirculated within the
system. The system includes a radiator, radiator fan,
water pump, engine water jacket, and thermostat. A
remote mounted engine oil cooler is also included.
Engine coolant flow through the oil cooler removes
excess heat from the engine oil as it recirculates through
the oil filter manifold and oil filter. Ancillary devices (not
shown) include a water temperature sensor and gauge, a
high temperature shutdown sensor and fuel shutoff
solenoid, and a DCA transducer.
The radiator fan and water pump are belt driven by the
engine crankshaft pulley. The water pump circulates
coolant whenever the engine is running. The pump
directs the coolant flow into a water jacket that surrounds
the engine cylinders and cylinder head. The water jacket
channels the output flow from the water pump to the
bottom of the engine. A thermostat housing is located at
the top of the engine. Increased fluid pressure within the
water jacket forces coolant to flow through either a
bypass port or output port in the thermostat housing.
The bypass port leads to the input side of the water
pump. The output port is connected to the radiator input
port. A pair of coolant hoses also provides a continuous
flow of coolant to and from the engine oil cooler.
When the engine is first started, the thermostat is closed.
The closed thermostat opens the bypass port to the
water pump and shuts off coolant flow to the radiator.
The coolant continues to recirculate through the water
pump, oil cooler, and water jacket while the engine
When the temperature of the recirculating coolant
reaches 177°F (80°C), the thermostat starts to open,
which diverts some of the coolant flow from the bypass
port to the radiator input port. When the coolant
temperature reaches 208°F (98°C), the thermostat
completely opens. The fully open thermostat shuts off
the bypass port, which sends the full flow of coolant to
the radiator input port. Increased fluid pressure within
the radiator forces an equal volume of coolant out of the
radiator output port and back to the water pump.
While the heated coolant flows through the radiator, the
radiator fan pulls a flow of outside air through the radiator
cooling fins, which removes heat from the recirculating
coolant. At normal engine operating temperatures, the
expected temperature drop across the radiator circuit
(input port to output port) is approximately 10°F (5°C).