With nearly 12 years and 1370 hours on my RV-4 I found blue fuel stains at the inboard end of my left fuel tank, extending out of the back baffle area. I pulled the tank and found the fuel stains originating at the bottom of the back baffle some 6 inches from the outboard end. It is hard to tell exactly where the leak begins. Some of the staining seems to be from the edges of the access plates I cut into the back baffle for resealing back in 2000 when I was readying the plane for first flight.
What annoys me is that the 12-year-old sealant (Pro-Seal at the time) is absolutely gooey to the touch all along the back baffle and the inboard fuel tank rib where the access plate is screwed on. I can just rub it right off with a finger tip. A search of this forum reveals this is a common problem. Apparently fuel leaking outside the tank in the presence of oxygen softens the sealant. I did mix the sealant by weight using a scale, so I don't suspect an incorrect mixing ratio.
I guess I will have to remove my back baffle access plates and confirm that the sealant is still firmly cured inside the tank. I will do the balloon pressure and soapy water trick first to pinpoint the exact leaking areas. I'll report back on what I find. I really don't want to pull the whole back baffle.
What annoys me is that the 12-year-old sealant (Pro-Seal at the time) is absolutely gooey to the touch all along the back baffle and the inboard fuel tank rib where the access plate is screwed on. I can just rub it right off with a finger tip. A search of this forum reveals this is a common problem. Apparently fuel leaking outside the tank in the presence of oxygen softens the sealant. I did mix the sealant by weight using a scale, so I don't suspect an incorrect mixing ratio.
I guess I will have to remove my back baffle access plates and confirm that the sealant is still firmly cured inside the tank. I will do the balloon pressure and soapy water trick first to pinpoint the exact leaking areas. I'll report back on what I find. I really don't want to pull the whole back baffle.