75MM pack howitzer recoil oil fill - anyone done it before

[dwing]

I am working on charging a pack howitzer's recoil oil. Nitrogen is charged and that went well. I fill up the oil reservoir, the oil indicator sticks out like it should, but when I take off the oil filling hose, recoil oil just pours back out. I thought there was a check valve on the inside of the gun that kept the oil from coming back out? is my check valve just froze? If so, how to unfreeze? Thanks for any guidance.

[P Bellamy]

Yes, there should be a spring-loaded valve between the filler retainer and the casing.
The exploded diagram of the filling valve assembly is at the bottom of page 66 in TM 9-1320 (April 44 edition), removal instructions are in para. 10 on the following page.

All the best,
PB