Motor Flush Valve
Motor Flush Valve.
(A) Closed loop circuit port. (B) Closed loop circuit port.
(C) Flush port.
Axle Propel Motor.
(1) Relief valve. (2) Crossover shuttle check valve.
The motor flush valve is located in the axle motor of the propel
closed loop circuit. Lines (A) -(A) and (B) -(B) represent both
sides of the closed loop circuit. The direction of tilt of the pump
swashplate, either FORWARD or REVERSE operation,
determines direction of flow in the loop. Direction of flow in the
loop determines whether a line is high pressure or low
Pilot pressure on the high pressure side shifts spring centered
crossover shuttle check valve (2). The low pressure side
opens to relief valve (1). The relief valve is set at 1724 kPa
(200 psi). The charge relief valve in the flushing vale is set at
1724 kPa (200 psi). Because the relief valve is set at a lower
pressure, charge pressure oil crosses the relief valve. Oil
flows through flush port (C) to the motor case. This oil cools
and flushes the motor and pump.
(1) Inlet port. (2) Outlet port. (3) Element.
Before being used in the two propel loops, charge oil passes
through the charge filter. During normal operation, charge oil
comes from the steering pump, enters the filter at inlet port (1),
and passes through the element (3). The element traps any
debris that is in the oil. Oil then exits the filter through outlet
port (2), and is routed to the propel pumps.
If the element becomes clogged with debris, the restriction to
the flow of oil causes a pressure increase outside the element.
If the pressure differential across the element reaches 350 kPa
(50 psi), the pressure of the oil causes the bypass valve to
shift. Charge oil passes directly through the bypass valve and
exits the filter through the outlet port to the thermal bypass
The filter has a manual indicator to show the oil is taking the
bypass route and an audible alarm sounds at 1205 kPa (175
psi) for low charge pressure.
Correct maintenance must be used to make sure that the filter
element does not become clogged, stopping the flow of clean
oil to the propel system.