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Sloshing Gas Tank Sealer

I was intrigued by this stuff. I had seen Por and Kreem and had even used epoxy to seal a bad tank. I figured that if people used this stuff in aircraft fuel tanks, it might just be up to the job of a bike tank. I blatantly swiped this from Aircraft Spruce so by all means, order it from them or from your local aircraft parts & supply house.
"Fuel Tank Sealer is a non-drying, elastic sloshing compound furnished at fluid consistency. Formulated to seal pinhole leaks around rivets and prevent corrosion in fuel tanks. Apply by spray or brush, or by fill and drain method. It is applied after cleaning tank and filleting lap joints. For aluminum or fiberglass tanks. Meets specification MIL-L-6047. One quart is sufficient for most light aircraft tanks." About $21 per quart
This new Randolph #912 Sloshing Sealer is recommended as a superior product to #802 Sloshing Sealer in fuel tanks using fuels containing alcohol.
CAUTION: These products have been used for many years to seal aircraft fuel tanks. However, due to the recent increased use of automotive gasoline as an approved fuel for certain aircraft, Sloshing Sealer is recommended for use only in those fuel tanks using aviation or automotive gasolines that do not contain certain additives such as methanol. Use of fuels containing such additives could result in deterioration of the sealer, resulting in serious engine problems. If there is any question regarding your brand of fuel, please check with your gasoline supplier. Not approved for use in aviation fuel tanks

I swiped this from the Beemer guys:

From: Thomas Nast Date: Mon, 27 May 1996 17:31:12 -0700 (PDT) Having just refurbished my second gas tank, I thought I would set the procedure out for posterity.

The gas tank must be restorable. For many years, BMW installed tanks with nice, water-absorbant foam rubber between the tank and chassis. The water would wick into the tank seams, and 18 years later the tank is junk. Forget restoring these, just buy a new one (2002 owners know this drill well) and install it with silicone sealant. If you can buy a new tank for under $3-400, it's a better way to go.

Remove the sending unit and any pumps, etc. in the tank. Detach the battery ground, put your cigarette out, pull the hoses and wire and extract the tank. Remove the fuel. Haul the thing to a radiator shop and have it boiled out. This will set you back around $100. Instruct them *not* to paint the tank after boiling. This process will remove a lot of the rust and scale, and all of the paint.

To treat the inside, you will need a gallon of MEK and a quart of Randolph's Sloshing Sealer (No. 912) (Is it coincidence this is named after the rustiest of Karmann-bodied Porsches?). These can be obtained from places that sell aircraft supplies. I get mine from Kenmore Air Harbor (Kenmore, WA). Figure about $60. Plug up all the holes in the tank. A junk fuel sending unit and gas cap can make this a lot easier (beg the dealer for these). Toss a quart of MEK in the tank and thoroughly slosh all sides and seams. I attach the tank to the frame holding my kids' swings using bungee cords; works great. Drain the tank in accordance with the zillion regulations you never heard of. (Hint: MEK evaporates *very* quickly.) Now take a few handfuls of clean pea gravel, and toss them into the tank with another quart of MEK. Do the sloshing routine again. You are really sanding the inside and chemically prepping it for the sealer. Drain, and make sure all the rocks come out. Let dry, then shake it some more for stones.

Now pour the whole quart of sealer in, slosh as before, then drain as much of the sealer out as possible into the can, and cover immediately. You can clean up mistakes with MEK (which is why you bought the extra two quarts). Wait about five minutes (the stuff will already be skinning) and do it again. Seal the can this time, and clean up.

If the tank has any vents, I blow them with compressed air to make sure they are clear. Put the tank away a day or two for the sealer to cure.

What you have now is a tank with a fuel-resistant plastic skin on the inside. You can paint the outside to taste. My procedure is to sand any rust, clean with paint reducer (Ditzler DTR 602), prime with a zinc-chromate primer (DuPont 2085S, which requires no catalyst) and use black Ditzler Delstar (DAR 9000) with flattener (DX 685) for the color coat. Delstar paints require a catalyst (DXR-80). If there are seams spray can't penetrate, I paint them with a brush just before spraying. This is much more durable than any factory or aftermarket painting, looks indistinguishable from new and really keeps the rust away. The paints can add to a little money if you don't have them lying around (I do keep them around, as they come in handy in all manner of restoration projects, from cast-iron radiators to ham radio towers). You can always resort to a spray can, or better yet, a body shop will probably shoot it for you for under $100, which is about what the paint would cost (with enough left over for another 24 tanks).

Th.B. Nast
"If it isn't rusting, I can't afford it."

Article By: David J. Morrow

Updated January 2005 

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