TM 5-3810-306-20
Oil Cooler
An air cooled hydraulic oil cooler is mounted on the right side of the superstructure. The oil cooler consists of a hydraulic
radiator, a hydraulic motor, a fan, and a fan guard. The fan is driven by the motor which receives its oil flow from the
pressure-beyond of the tele/rear steer/lift valve bank. The fan blows air through the cooling fins on the cooler. All of the
hydraulic oil returns (from the major crane functions) through the dual return lines via swivel port No. 11. This line has a
15 psi (103.4 kPa/1.03 bar) in line check valve which is normally closed and does not permit flow. Normally all oil is routed
to the return manifold, through the oil cooler, and on to the hydraulic filter in the reservoir.
When several hydraulic functions are being used at one time (i.e., hoisting, lifting, and telescoping), more oil has to flow
through this one line causing a pressure buildup in the dual port return system. When this pressure reaches 15 psi (103.4
kPa/1.03 bar), the normally closed check valve will open and permit some oil to bypass the oil cooler and flow directly into
the reservoir filter. When fewer functions are being used, the pressure in the system will decrease below 15 psi (103.4
kPa/1.03 bar) and the check valve will close.
As mentioned above, the oil cooler fan motor is driven by oil from the tele/rear steer/lift circuit when the control valve is in
neutral. If any of the three functions is activated, the oil exhausts directly into the return manifold and the fan motor stop s
running. In addition, if the temperature of the oil in the return manifold falls below 111 degrees F (44 degrees C), an oil
bypass valve will direct oil around the motor, causing the motor to stop. The motor will restart when the oil temperature
reaches 120 degrees (49 degrees C).
Oil Cooler Motor
The hydraulic motor consists of two meshed gears in a closely fitted housing with inlet and outlet ports opposite each
other. The two gears mesh and rotate together with only one gear coupled to the drive shaft. The motor torque is
developed through pressure on the surfaces of the gear teeth. Oil enters the inlet exerting pressure on the gear teeth
causing them to rotate. Oil is carried to the outlet port in chambers formed between the gear teeth and housing.
Hydraulic Pump Disconnect
This disconnect assembly is provided for cold weather starting and consists of a housing, lever, movable collar, and a
sliding splined sleeve. Moving the lever actuates the movable collar within the housing which in turn slides the splined
sleeve on the splined pump shaft to engage the sleeve with the splined shaft of the torque converter drive. The disconnect
housing is initially filled with one pint of transmission fluid and during operation the torque converter will spray transmission
fluid into the housing to lubricate the disconnect.
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