Strange hydraulic pump pressure observation

[Sdexta62mi]

I just finished rebuilding my lift cover and wanted to check pump pressure. I observed something strange and was curious if anybody has noticed this with there tractor. I connected a gauge to the auxiliary service outlet, pulled out the Aux. service valve and moved the hydraulic control to the top of the quadrant. The gauge quickly rose to 2000 psi and then began to fall to about 500 psi. The only way I can get it to raise pressure again after this happens is to lower the control lever and raise it again. Shouldn't the pressure hold at pump relief pressure when the control lever is at the top?

Larry
Michigan, Usa

[Emiel]

Larry,

The behaviour of your relief valve is almost correct. According to the manual it should blow of between 2100 and 2300 LBS and maintain about 600 LBS after blow of.

If it were mine, I would leeave it this way and not re-shim the relief valve.

rgds

Emiel

[henk]

Hello Emiel,

Thanks for helping us out on some matters.

[Sdexta62mi]

Thanks for the help Emiel. It just seemed strange that the pressure would fall and hang at a lower pressure, it seems to act like an unloading valve. Do you have any idea what the purpose of this is for?
thanks

[Emiel]

Hi,

Think this to make sure the system is not overloaded on a continous base.

It's an open center design, not a closed center which trys to remain pressure at a constant level.

rgds

Emiel

[Sdexta62mi]

Makes sense, thanks for helping me understand