so, i have a 1987 S4 Tii, and I have a big fuel leak.
It only happens when the tank is over 3/4 full, it leaks out of where the sender unit gets bolted down.
I have put in a new gasket, and used fuel rated sealer on both sides
I took the sender out and look to see if the mounting part was warped, it was, i straightened it out.
Made sure the surface was clean where the gasket goes.
I would tighten it down more, but afraid of stripping the bolts.

What do I do, im at a loss...

 

Is it possible that the small fuel hose in the sender assembly is spraying upward once your fuel line gets pressurized?
Is your evap system working?

 

I’ll make sure the hose is good, but pretty sure it is. I’m not sure if the evap is bad, but I opened the gas cap and it still happened