Fuel Stains on Wings

[jiott]

I seem to be unable to keep fuel from coming out of the wing tank caps on my SS7 whenever the tanks are about 3/4 full or more. I believe the caps are tight and the fuel appears to come out the vent tube. I almost always notice fuel stains on my wings after landings where I used a slip to get down over trees, which I do fairly often. This is becoming a real irritation because the stains are not easily washed off. Anyone have any tips on how to gets the stains off and how to prevent them in the first place. Even when I don't slip it seems to come out with 3/4 tanks. Does everyone fight this on a regular basis?

[Av8r3400]

Short answer is: Yes.

I have had good luck with the "Mr Clean" Magic Eraser to remove the stains. (and the ones by the sump drains that leave that extra drip…) If you scrub too much it will start to take off the paint, though.

I changed out my gas cap gaskets with some I got from my local FBO, they were for a C150. Cost me $10 for the pair. They fit a lot tighter that the old ones, but there is still some spillage if the fuel level is high. If I have less than 3/4 tanks and the problem goes away.

[beeryboats]

I've been wondering about the lack of gaskets on my mod IV. Even without gaskets they are difficult to get tight.

[Peteohms]

Zep Heavy Duty Citress Degreaser works for me removing fuel stains.

[Paul Z]

I used bug and grease remover for cars. It works pretty well I'm going to try the Mr Clean Eraser. I have a hint of stain. As far as preventing it in the future I'm trying some Wax & Dry spray on wipe off. I'll have to check the brad tomorrow. Steve Kellendar mention some gas cap seals for a Mercedes Benz that work really well. I been wanting toget in touch with him to get the part number, I replaced both of mine when I went up to Oshkosh, but the right tank still leaks. I would bet it is the gasket and not the vent tube.

[DesertFox4]

Paul, here is the Mercedes "gas cap gaskets" with part number on the bag.


Mercedes Part# 140-471-00-79


user141_pic3209_1336366781.jpg

This photo shows where to fill the small holes with J.B.Weld so the cap does not leak out the rim while flying. Fill all 4 holes where the yellow marker is pointing.

user141_pic3211_1336366781.jpg

[HighWing]

I think there are a couple of issues here. First and as mentioned, replace the gaskets. The ones original with the caps - at least in the two Model IVs I have experience with are simply junk. I would go with the Mercedes replacement - they work.

Then one day on the way back from the Desert Fox fly-in years ago, I unwisely had the line guy fill the tanks. He didn't seat the cap on the right wing properly and my first indication was the fuel in the sight gauge dropping almost as I watched it. We landed in Eli and without mishap. The point - on the top of the wing there definitely is a negative pressure and if the fuel level is even close to the filler neck, it will suck the gas out of the tank. A side slip with a poorly fitting gasket will not only leak but will become a fountain due to the negative pressure on the top of the wing.

Talk in the past regarding removing avgas stains also included using the fuel itself as a solvent with positive results. I have never had to try it, but this from reports.

[Paul Z]

Paul, here is the Mercedes "gas cap gaskets" with part number on the bag.


Mercedes Part# 140-471-00-79


user141_pic3209_1336366781.jpg

This photo shows where to fill the small holes with J.B.Weld so the cap does not leak out the rim while flying. Fill all 4 holes where the yellow marker is pointing.

user141_pic3211_1336366781.jpg

I plan on ordering a set, they are Blue they match my plane. I'm order them now, now that I have my paypal Password figured out. They will ship in 3 days.

$14.95 at Mercedes Benz Online parts, http://www.mbonlineparts.com

[jiott]

Thanks for all the info. I will try the Mercedes gaskets, but I think its coming right out the vent tube when tanks are 3/4 or more. I will also try some of the cleaning methods mentioned.

[jamesmil]

I found that my right tank would leak badly from the cap the first time I topped off the tanks? Made a mess on top of the wing and down the side of the fuselage . I had never topped the tanks off so as to keep it light to land on the beach , had over 100 hr, on it before I need to top it off, after I got back home and inspecting the cap I found the front tab of the cap was bent a down a little and was not sealing the cap at the front. Bent the tab to get a good seal and fixed the leak when full. As for cleaning the stains I use 3m adhesive remover. Comes in a red and white quart can with a small plastics squirt nozzle. Be sure to reapply a coat off wax after using as it will take all the wax off but doesn't cut the paint. We used aero thane paint not sure about other paints so should try a test spot first. Hope this helps