The International Cessna^® 170 Association

I have not investigated yet but it looks like I might have a slight fuel leak on the left tank of my 170B. The last two times I have filled her up to the neck, flew, and put the plane away relatively full, only 0.5 hrs or less flown the same thing has happened. After returning a few days later I noted a very small drop of what looked like oil coming off the trailing edge of the wing in the area of the tank. It looks and feels like oil What I am thinking is that the fuel is washing out some of the corrosion X the wings were once sprayed with.

Any way the question is what kind of repair work can be done to a fuel tank?

Frainiea

Unless you have more reason to suspect fuel leaks, I wouldn't jump to conclusions about the tank being a problem.
First it's more likely that a gasket at the fuel gauge, or a short hose at the vent line, etc. is the problem, in which case the fix is relatively easy.
But more likely, some spilled fuel (if indeed you find the smell of fuel and the stain of fuel present) is all that caused it. Even MORE likely is the chance that the anti-corrosion treatment is simply weeping, as that is a very common complaint.
Remove the wing root fairing and look inside the wing for evidence of a fuel leak and confirm that first.

What does the oil like substance look and smell like? If you are using 100LL a fuel leak will be blue and smell like fuel. If the leak is slight, it can thicken as it dries but it will still smell like gas. On the other hand, the corrosion inhibitors have their own unique smells so that might help identify it. Do you have any other weeping anywhere else on the fuselage? Normally the corrosion treatments will be coming out several places, anywhere there is a seam or rivets.

If your tank is leaking, they can be repaired.

Keith N.