3-Point Hitch MF 135 Pump Control Valve Leak

[klancf51]

Does anyone know the cause of this leak? The picture was taken when the lift was leaking down.
Thanks!

[klancf51]

This leak is caused by a failure of the pump control valve diaphragm (898254M91). The pump control valve has a weep hole on the bottom of the non-pressurized side of the valve as shown in this photo:
).

When the diaphragm leaks under pressure, hydraulic fluid will exit via the weep hole. Here is a photo of the failed diaphragm:

Note that the failure was due to the rubber becoming hardened and cracking off of the fabric backing material. In my case the fluid leakage was less when the pressure was greater because the diaphragm moved against spring and the flow was restricted as the fabric gap closed.

fyi.