E34 fuel sender unit leak

[Kamz e34]

Hey
My e34 fuel sender unit is leaking when i have a full tank, u can see fuel around it. I replaced the rounded seal, the fuel sender unit, the hoses and the black ring that tighten it. And i still have the problem. I am really pissed off with this. What can the problem be?

[shogun]

http://bmwfans.info/parts-catalog/E3...e/fuel_supply/
have you checked expansion tank tubing? http://bmwfans.info/parts-catalog/E3...n_tank_tubing/

[Kamz e34]

What is an extension tank? First time i hear about it.
The problem was that the black ring needed to be more tightened. Thank you

[shogun]

every car has an expansion tank, same reason like the coolant expansion tank for coolant, when the fuel expands due to temperature increase it needs a way to go. Expansion tanks are not only for emissions, they prevent fuel spills, thus saving fuel, reduce fire risk, and prevent spilled fuel from being emissions. So fire safety and economy are also purpose of the the overflow tanks purpose.