Hydraulic System
35
HyDRAULIC PUMP
The hydraulic pump distributes hydraulic fluid to the steering gear and the hydraulic fan motor. The
hydraulic pump mounts on, and is driven from, the rear of the air compressor.
Operation
The hydraulic pump is a tandem gear type pump which has two separate in-line hydraulic gear pumps.
The larger pump at the front of the pump provides hydraulic fluid for the engine cooling fan motor. The
smaller pump at the rear of the tandem pump provides the hydraulic fluid to the power steering gear. The
power steering pump circuit in the tandem pump includes a pressure relief valve set to relieve at 2175
PSI, and a flow control valve to limit the power steering flow to 3.2 to 4.0 GPM. There is no pressure
relief valve for the fan motor circuit in the pump. Pressure relief for the fan motor circuit is provided by
a relief valve at the motor.
The hydraulic fan motor is temperature activated and may start at any
time when the engine is running. Always disconnect the battery ground
cables to preclude accidental engine start while working on the hydraulic
system.
The hydraulic fan motor has a control valve that is preset by the
manufacturer. DO NOT attempt to adjust this valve. Tampering can
cause injury and possible fire due to excess pressure causing failure of
the hoses, pump, or fan motor.
Hydraulic Fluid
The fluid in the hydraulic system is selected to accomplish all of the various demands placed on it by the
system performance parameters. Please refer to the “Fluid Specifications” section of the Specifications
chapter for the type of fluid to use in the hydraulic system.
Summary of Contents for LOW FLOOR
Page 18: ...Specifications 18...
Page 58: ...Preventive Maintenance 58...
Page 110: ...Engine 110...
Page 138: ...Transmission Driveline Rear Axle 138...
Page 182: ...Suspension 182...
Page 260: ...Air System 260...
Page 420: ...Electrical System 420 Deutsch DT Series Connectors...
Page 421: ...Electrical System 421...
Page 422: ...Electrical System 422 Deutsch HD 10 Series Connectors...
Page 423: ...Electrical System 423...
Page 424: ...Electrical System 424 Deutsch HD 30 Series Connectors...
Page 425: ...Electrical System 425...
Page 442: ...Heating Air Conditioning 442...
Page 492: ...Body and Interior 492 Figure 11 33 USSC Seat Assembly...
Page 493: ...Body and Interior 493 Figure 11 34 USSC Seat Suspension Assembly...
Page 495: ...Body and Interior 495 Figure 11 37 Seat Air Connections...