12M Series 3, 140M Series 3, 160M Series 3, 140, 150 and and 160 Motor Graders General Information (Hydraulic System) Caterpillar

General Information (Hydraulic System)
1.1. Implement Control Valves
2.1. Implement Pilot Oil Filter
3.1. Control Manifold
4.1. Shut-off Manifold
5.1. Hydraulic Tank
6.1. Piston Pump (Implement and Steering)
7.1. Pump Control Valve
8.1. Oil Filter (Hydraulic Return)
9.1. Joystick Controls
10.1. Centershift Lock
11.1. Blade Accumulators (If Equipped)

Reference: For more information, refer to AVSU1496 , "12M3 Motor Grader Hydraulic System" on AVSpare Channel1


Note: A CWS login is required to access AVSpare Channel1.

Illustration 1g03504476
(1) Hydraulic tank
(2) Rear control valve stack
(3) Blade lift cylinders
(4) Front control valve stack
(5) Articulation cylinders
(6) Implement Electronic Control Module (ECM)
(7) Joystick control
(8) Shutoff valve
(9) Center shift lock
(10) Blade tip cylinder
(11) Side shift cylinder
(12) Center shift cylinder
(13) Swivel
(14) Circle drive motor
(15) Wheel lean cylinder
(16) Blade accumulators (If equipped)
(17) Oil filter (Hydraulic Return)
(18) Implement pump
(19) Pilot control manifold
(20) Oil filter (Pilot)

This module discusses the features and operation of the implement and steering system. The following motor graders are covered in this module:

  • 12M Series 3 Motor Grader

  • 140M Series 3 Motor Grader

  • 160M Series 3 Motor Grader

The hydraulic system is a proportional priority pressure compensated system. The PPPC system is a load sensing system. The PPPC system uses a load sensing pump for the implement and steering to perform the pressure compensation function. The implement control valves have an internal flow compensator. This flow compensator performs the proportional priority function.

The implement system has the following main components:

  • Implement control valves

  • Implement pilot oil filter

  • Control manifold

  • Shut-off manifold

  • Hydraulic tank

  • Piston pump (implement and steering)

  • Pump control valve

  • Oil Filter (hydraulic return)

  • Joystick controls

  • Hydraulic cylinders

  • Centershift lock

  • Blade accumulators (if equipped)

Implement Control Valves

The implement control valve regulates the operation of each implement. Each implement control valve contains a compensator valve. The compensator valve distributes the oil flow that is available. The implement control valve may contain a relief valve. The relief valve will protect the rod end of the cylinders from thermal cycle.

Implement Pilot Oil Filter

The pilot oil filter removes debris from the pilot oil for the implement solenoids.

Control Manifold

The pilot control manifold directs pilot oil to the solenoids of the implement system. The control manifold contains a main relief valve, a secondary steering relief valve, and a pressure reducing valve. The control manifold also contains a pressure port for the pilot, implement, and steering system, and an SOS port, and a pressure sensor.

Shut-off Manifold

The shut-off manifold contains a solenoid that will direct or inhibit pilot oil to the solenoids of the implement system. Direction or inhibition is based on the implement lock-out switch position in the cab. The shut-off manifold also contains a shuttle valve. The shuttle valve sends the appropriate load sense signal from the implement or steering system to the pump control valve.

Hydraulic Tank

The hydraulic tank stores oil for the hydraulic system.

Piston Pump (Implement and Steering)

The piston pump for the implement and steering is a variable displacement axial piston pump. When the engine is operating, the pump will produce flow to satisfy the following conditions:

  • The demand of the steering system

  • The margin pressure of the pump

  • The demand of the hydraulic implements

  • The internal lubrication of the pump components

Pump Control Valve

The pump control valve keeps the pump pressure and the pump flow at a level to fulfill the requirements of the implement and steering system.

Oil Filter (Hydraulic Return)

The return filter removes debris from the hydraulic system. The return filter prevents debris from entering the hydraulic tank.

Joystick Controls

The joystick controls send an electrical signal to the solenoids of the implement system.

Centershift Lock

The centershift lock is actuated by oil from the implement pilot system. The centershift lock receives pilot oil from the pilot control manifold. The centershift lock switch sends a signal to the solenoid for the centershift lock to actuate the centershift lock.

Blade Accumulators (If Equipped)

The blade cushion accumulators dampen the shock that is made in the blade lift hydraulic circuit. This shock occurs when the blade contacts an object that will not move. The blade cushion accumulators have a nitrogen precharge pressure that provides the cushion.