Work vehicle with hydraulic assist for power off steering

1. A work vehicle, comprising:

a chassis;

a plurality of ground engaging members carried by the chassis;

a hydraulic steering system connected with at least one of the ground engaging members, the hydraulic steering system including a steering hand pump;

a hydraulic main supply line fluidly coupled between a pressure source and the steering hand pump, the main supply line including a check valve;

a hydraulic sub-system powering a component of said work vehicle other than said hydraulic steering system and wherein the hydraulic steering system and the hydraulic sub-system are independently powered relative to each other including a pressurized access point; and

a normally open, two position valve including an inlet fluidly coupled with the pressurized access point, an outlet fluidly coupled with the main supply line on a downstream side of the check valve, and a pilot port fluidly coupled with the main supply line on an upstream side of the check valve, the two position valve being operable in the closed position based on pressure in the main supply line when the main supply line is pressurized from the pressure source, the two position valve being operable in the open position and interconnecting the pressurized access point with the main supply line through the outlet when the main supply line is not pressurized from the pressure source.

2. The work vehicle of claim 1 , wherein the pressurized access point includes a fluid port or a fluid line.

3. The work vehicle of claim 2 , wherein the work vehicle is an agricultural combine and the hydraulic sub-system includes a cleaning fan drive with a cleaning fan valve having a diagnostics port, and the pressurized access point is the diagnostics port.

4. The work vehicle of claim 1 , wherein the valve is a normally open, two way/two position valve.

5. The work vehicle of claim 4 , wherein the valve is mechanically biased to the open position, and pressure within the pilot port moves the valve to the closed position when the pressure in the main supply line is above a preset value.

6. The work vehicle of claim 5 , wherein the valve is mechanically biased to the open position when the work vehicle is in a road mode.

7. The work vehicle of claim 1 , wherein the hydraulic steering system and the hydraulic sub-system are independently powered by a power take off (PTO) coupled with an internal combustion (IC) engine.

8. The work vehicle of claim 7 , wherein the pressure source is powered by the PTO.

9. The work vehicle of claim 1 , wherein the plurality of ground engaging members each include a wheel, track or half track.

10. The work vehicle of claim 1 , wherein the work vehicle is an agricultural combine.

11. A steering system for a work vehicle, comprising:

a steering hand pump;

a hydraulic main supply line fluidly coupled with the steering hand pump and including a check valve; and

a normally open, two position valve including an inlet fluidly couplable with a pressurized access point of a hydraulic sub-system for a component of the work vehicle other than said hydraulic steering system, an outlet fluidly coupled with the main supply line on a downstream side of the check valve, and a pilot port fluidly coupled with the main supply line on an upstream side of the check valve, the two position valve being operable in the closed position based on pressure in the main supply line when the main supply line is pressurized from a pressure source, the two position valve being operable in the open position and interconnecting the pressurized access point with the main supply line through the outlet when the main supply line is not pressurized from the pressure source.

12. The steering system of claim 11 , wherein the valve is a normally open, two way/two position valve.

13. The steering system of claim 12 , wherein the valve is mechanically biased to the open position, and pressure within the pilot port moves the valve to the closed position when the pressure in the main supply line is above a preset value.