1964 'E' Water in Fuel

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2 weeks 4 days ago #3550 by STEVE ELLS
Replied by STEVE ELLS on topic 1964 'E' Water in Fuel
Hi Jim;
The fuel tank in your 172 is a sheet metal tank that's held in place by straps. You gain access to the tank by removing the sheet metal over the fuel tank bay.

I have seen these tanks leak because, at some time in the past, someone didn't fully support the fuel tank nozzle while filling the tank; instead the inserted the nozzle and let the tanks filler support the weight of the nozzle/hose. Cracks take place around the filler neck.

There's a method using very slight air pressure (2 psi) to pressurize the tank before spraying soapy water around the filler neck. Bubbles will show you exactly where the leak is.

But be very careful, you'll need a regulator to get shop air down that low. If the pressure is any higher you have a very good chance of deforming the tank.

If the crack is very long, it's best to take the tank to an experienced aluminum welder that has welded fuel tanks before. There's a large potential for an explosion unless the tank is empty and the fumes have been purged. One method I have heard of purging the fumes is to add some dry ice to the tank and let it purge for at least 24 hours before taking action.

You can try to stop the leak by applying Chemseal fuel tank sealant on the outside. You can do your best to clean the area using Acetone (hardware store) and a stainless steel tooth wire brush. This usually doesn't work very well because it's hard to get the area clean enough for the Chemseal sealant to effectively stick. You can get the Chemseal sealant from Aircraft Spruce and Specialty. Here's a link:https://www.aircraftspruce.com/catalog/appages/chemseal09-04612.php.

Let me know what you decide to do.

Best,
Steve

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2 weeks 4 days ago #3549 by GARY PALMER
Replied by GARY PALMER on topic 1964 'E' Water in Fuel
Have you done anything to ensure the top flange of the tank opening is flat? If there is a bend or warp, then it may prevent a clean seal of the gasket. I would be making it up to suggest a way to check; I think like a dentist, a piece of carbon paper in a block of wood slightly tapped on the open tank. Check for an ink deposit all around.

Now I admit this is a guess and I am not saying you should deposit quantities of carbon flakes in your tank. But there has to be something. Maybe a crayon on the tank flange and then paper and wood to transfer an imprint on the paper? Anyway, that is just a suggestion, YMMV and always be careful you do not accidentally contaminate fuel.

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3 weeks 2 minutes ago #3544 by Jim Pantas
1964 'E' Water in Fuel was created by Jim Pantas
We have replaced all of the gaskets on both tanks but I am still getting water in my sumps.

I am fairly certain it is seeping in around the filler neck, is there any solutions/modifications/magic goo that remedies it?

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