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Fuel Leak

captainglen

Entry posted by captainglen

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blog-0153602001417278989.jpgTo a lot of Mooney owners a fuel leak can seem quite intimidating especially to those owners who do not hold an A&P rating. I must admit that I was intimidated at first. A small amount of leak (a seep) is permitted per the Mooney service manual as long as it is not into an unvented area so top of wing or gear bay is permissable but cabin, outboard wing area or leading edge are not.

My seep was into the leading edge and over 4 months drained the left tank dry; not enough to leave a stain on the ground but enouch to stain the stain the bottom of the wing adjacent to the leading edge drain hole. This meant the leak had to be at the bottom inboard corner and the blue fuel dye stains confirmed. As it turned out the hardest part of the job was getting the tank inspection cover open without damaging the wing. Scraping the old sealant was a bit tedious but really only took a couple of hours.

Using a A-2 gave a lot of work time on a cool day and working with a brush which I had trimmed the bristles to 1/2". I sealed way beyond the leak area to make sure that no fuel could work it's way under the repair.of course I cleaned the area and roughed the surface of the factory sealant.

To close the tank I used an B-2 wich is not what I would reccomend because it is way to slow, a B-1/2 would be much better. There is an A/D to inspect the stringer and rib drains to make sure you have not clogged them before you close the tank. I allowed a whole week to cure before filling the tank for a leak check and another week before checking for leakage. I am absolutely 100% leak free for $80 worth of supplies.

For those among you who are not certified mechanics there are mechanics who are willing to work with owner assistance. I know of one on my home field who supervised a non mechanic owner in replacing an entire cylinder set (top overhaul). There isn't much room inside the tank for two pairs of hands but most mechanics would gladly defer the prep work to someone else.

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Wakeup

I'm in the process of having my tanks stripped and resealed. Did you check any filters for debri and when do you check? Looks like a lot of debri will be floating around after cleaning? I will be scared on my first few flights thinking debri is floating around. Thanks. Troy

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captainglen

I would not so much worry about floating debris unless you use the tank down to the last couple of quarts. The screen (not filter is at the low point in the tank so would worry more about sediment sloshing near the bottom or suspended in the fuel. The tank needs to be clean before and after sealant is applied. Another point as many repairs have been discovered to have clogged rib and stringer drains which could render some fuel unusable. This why there is an A/D post repair inspection.

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captainglen

I sealed the whole inboard bay, there is also an outboard bay. I used a plastic scraper of the type we use to strip 737 tanks; I would have preferred micarda. I used no solvents but there are solvents I have heard will soften tank sealant. I do see you realize that stripping is the hardest part of the job.

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Wakeup

I checked on the status of my tanks today. I was surprised to see how small the actual tanks are in the wing. I was thinking most of the wing was the tank. It's hard to believe a compartment that small can cost so much. Troy

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captainglen

Type A sealant is easiest to work and can be applied with a brush and can be applied thinly at places and thicker near seams. Type B sealant Is thick and has to be spread with a tool and not good for much except closing the covers and filling the gaps. The numbers after the type or class letter is the time the sealant will remain workable after mixing at 72 degrees. Thus A-1/2 will remain workable for 1/2 hour while A-2 will remain workable for two hours.

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