Chassis Information
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WINDSOR
10•296
Hydraulic Cooler
to approximately 14.5 psi. Hydraulic system pressures with a system at no
load may be as low as eight bar on the output side of the pump. This is due
to the hydraulic fluid flow slows from hydraulic fluid restriction and creates
pressure.
This may be understood as a faucet with a garden hose attached.
Crimping the hose with the faucet on will create pressure from the restric-
tion. This principal applies to the hydraulic system. The hydraulic pump is
the supply, the load would be the power steering gear or the hydraulic fan
motor. Hydraulic system pressure at full load can exceed 130 bar or 2000 psi.
Hydraulic system pressure falls dramatically after the load. The return line
pressure may be as low as six to eight bar. The fluid enters the hydraulic
cooler where the heat is dissipated.
The hydraulic cooler is an important part in the hydraulic system. This
helps keep the hydraulic fluid from overheating. When a load is placed on
the hydraulic system, heat is created in the fluid. the hydraulic pump builds
pressure creating heat in the fluid. The restriction from the loads applied also
creates heat. This heat must be dissipated to keep the hydraulic fluid from
overheating and breaking down. After the fluid is cooled the fluid is filtered
before returning to the reservoir.
Care must be used when starting an engine in very cold or arctic climates.
As with any oil, lower temperatures thicken the oil hydraulic system pres-
sures increase due to the thickness of the fluid. Even though the hydraulic
pump is equipped with pressure relief valves the thick oil on the return line
can exceed the operating pressure of the hydraulic cooler.
The hydraulic fan drive system cools the radiator, charge air cooler,
hydraulic fluid cooler. transmission cooler and and the dash air conditioning
condenser. The components of the hydraulic fan system are: hydraulic reser-
voir, filter, pump, fan motor, switching valve and thermovalve. The cooling
fan speed is proportional to engine speed and radiator temperature. When
radiator temperature rises above 185° F, the wax thermovalve slowly closes
off the bypassing hydraulic fluid from the switching valve. A spool valve
begins to move in the switching valve. This directs the pressurized hydraulic
fluid to the fan motor. The higher the radiator temperature, the further the
spool valve is moved in the switching valve, providing a higher volume of
pressurized hydraulic fluid to the fan motor. Fan motor speed is increased to
meet the demand for cooling. The action of the thermovalve is designed to
move the spool in the switching valve to ramp up fan motor speed. This
design saves horsepower and increases fuel mileage by precise control of
hydraulic fan motor speed. The fan motor will increase in speed when the
Hydraulic
Fan System
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