Fuel leaking BETWEEN main tanks?

[Skymaster337B]

My simple advice is to move the fuel selector valves to the "OFF" position when the aircraft is not in operation. I've noticed "seepage" thru the 40+ year old fuel selector valve, when the aircraft is parked and fuel selector valves are on.

I think it has something to do with the combination of ground level, and the fuel trying to seek gravity, and possibly the vent system. Do you know if the fuel caps are original or are in compliance with AD 79-10-14R1. Also there's a check valve in the wing tips that will help vent the tanks, but may also become clogged.

Do you keep the aircraft registered under the FAA or with Australia's version?

Keep us posted.