3x20 and 4x20 hydraulic system and Ehydro. question about how they function

[Danscaper]

Im pretty sure the hydraulics and ehydro on both series tractors are basically similar. Correct me if im wrong, but the tractors have a steering pump and an implement pump mounted side by side on the engine. Next we have the eydro pump which seems to be plugged right into the flywheel via torsion dampener.

My question is this; Does the implement pump always send fluid even when its not called for to the Control valve for the loader? In other words does it bypass in the valve and continusly get recycled back to the resivoir? On these machines you always hear a steady hum coming from the control valve that gets louder with rpm advance. My particular model has electronic scv in the rear so the question also relates to this. I figure it must always get supplied because how does this electro scv work? What causes this humming sound in the control valve?

 

[jenkinsph]

The implement section is always pumping when the engine is running, typical "open center system" using a fixed displacement gear pump. As you said it circulates through the valve and get dumped back into the reservoir.

Lots of things can cause noise and hum, the oil moving at a high velocity, the fluid changing directions, friction and air in the system probably a bunch more things too.

 

[Danscaper]

What pump operates the 3 ph? is that the implement pump as well? Thanks for the reply

 

[arlen4720]

Yes, it is the implement pump. It feeds the 3 point, and all of the SCV's, and operates the pto clutch/brake. The power steering pump takes care of the power steering and the "charge flow" (makeup flow) for the hydrostat pump/motor loop, and pushes oil through the oil cooler. The steering pump and the implement pump are fixed displacement gear pumps, and the hydro pump is a variable displacement piston pump.
All three spin whenever the engine is spinning. The hydro pump "destrokes" so it is not moving any oil when the foot pedals are not pressed.