3040 JD hydraulic oil leak Help needed.

[HumphreyUK]

I have a John Deere 3040 tractor that is losing a lot of oil from a cylindrical tank above the oil cooler and radiator. The previous owner simply put a hose into a drum to collect the oil and reused it.
The cylindrical tank has a banjo connection on the top that the oil is coming from. It is connected to the suction side of the hydraulic pump driven from the front of the engine.
I was wondering if the tank contains an expansion balloon that has burst. I simply have no idea what the problem is and what to do to cure it.
Thank you for any replies.
Humphrey
ps I think it is the transmission header tank.

 

[DLTTrekkers]

expansion balloon .....no ! Oil comes from the main seal in the mainhydraulicpump to the top off the tank and then back to the gearshiftcover. That "bolt" ontop of the tank has a oneway checkvalve that prevents oil from entering that small tube . Check that valve !

 

[HumphreyUK]

I will do that tomorrow and thank you for your help. We tried to undo it but thought it might shear off.

 

[HumphreyUK]

Seems that the pipe that should have returned to the gearshift cover was broken off and never re-connected. It took 40 litres of oil to refill.