GEAR 4H8576 - Caterpillar

Illustration 1 g01046598
Secondary steering system (1) Steering metering pump (2) Steering cylinders (3) Primary steering pressure switch (4) Secondary steering pump (5) Tank (6) Steering pump (7) Priority valve (8) Steering check and combiner valve (9) Check valves (10) Line from secondary lower valve (11) Shuttle valve (12) Check valve (A) Oil from the hoist pump (B) Return oil (C) Oil in the load sensing systemThe secondary steering pump is driven by an electric motor. The secondary steering pump will automatically provide oil flow in order to operate the steering when the steering oil flow falls below the required rate. A pressure switch (3) is located in steering check and combiner valve (8). This pressure switch sends a signal to the electronic control module (ECM) when the steering pressure drops below a certain pressure for a certain duration. The ECM will then activate the secondary steering pump.The ECM will also activate the secondary steering pump if the momentary switch in the cab is pressed.The steering pump and the secondary steering pump are connected to steering check and combiner valve (8), which is connected to steering metering pump (1) .When the engine is running normally, steering pump (6) supplies the steering metering pump through the steering check and combiner valve.Steering pump pressure holds the control switch of the secondary steering pump in the open position. The secondary steering pump motor is switched off and secondary steering pump (4) is stationary.If oil flow from the steering pump is lost for any reason during movement of the machine, the pressure switch for the secondary steering pump will close. (This could be due to the engine stopping or this could be due to a pump failure.) This will send a signal to the ECM, which starts the drive motor for the secondary steering pump and the secondary steering pump delivers oil through the steering check and combiner valve to the steering metering pump.Steering Check and Combiner Valve
The steering check and combiner valve connects oil flow from either the steering pump or the secondary steering pump to the steering metering pump.The steering check and combiner valve contains the pressure switch for the secondary steering pump and an outlet to the secondary lower valve.
Illustration 2 g00586090
Steering check and combiner valve (1) Outlet port to the secondary lower valve (2) Check valve for the secondary steering pump (3) check valve for the steering pump (4) Port for the control switch for the drive motor for the secondary steering pump (5) Inlet port from the steering pump (6) Inlet port from the secondary steering pump (7) Outlet port to the steering metering pump (8) Pressure test point for the secondary steering system
Illustration 3 g00632342
The steering check and combiner valve is located at the left front of the tractor in front of the hydraulic tank.