Monaco SIGNATURE 2001 series, Owner'S Manual

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specified pressure limit, the internal by-pass relief valve will be forced open
to keep the hydraulic fluid at operating pressure. The hydraulic pressure gen-
erally is not rated in psi but is rated in the term bar. One bar is equivalent 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 of the pump. When a load is placed on the hydraulic
pump, such as turning the steering wheel, 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
motors. 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 cooling, 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 the dash air conditioning con-
denser. The components of the hydraulic fan system are: hydraulic reservoir,
filter, pump, two hydraulic fan motors, hydraulic switching valve and ther-
movalve. Cooling fan speed is proportional to engine speed and radiator tem-
perature. When radiator temperature rises above 185º Fahrenheit, the wax
thermovalve slowly closes off the bypassing hydraulic fluid from the switch-
ing valve. As radiator temperature rises a spool valve begins to move in the
switching valve. This directs the pressurized hydraulic fluid to the fan
motors. 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 motors. Fan motor speed is increased to meet the
demand for cooling. The action of the thermovalve is designed to move the
Chassis Information
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S I G N A T U R E
1 0 • 3 0 1
Hydraulic Cooler
Hydraulic Fan
System