Fuel tank leak

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thecantaloupeman

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So my 78 C20 is leaking fuel from the filler neck. The hose looks like it isn't a problem because it is leaking from where the hose meets the tank. I thought it might be the clamp so I replaced that, but it didn't fix the issue. I am wondering if something could be wrong with the nipple on the tank? Any ideas? Thanks.

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deve05

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Had the same problem on my 84 when I bought it and it was due to corrosion on the tank neck. I removed the hose and used a cutting wheel fitted with a metallic brush and polished the neck. I used a rolled up paper towel stuffed into the neck to prevent debris from getting in and a vacuum cleaner to suck out the debris and paper towel after cleaning.

I then cleaned out the interior of the hose with 620 grit sand paper about as far back as the neck will go. I treated the neck with aircraft alodine sealer to prevent future corrosion and reinstalled the hose and put in a new clamp.

This was 4 years ago and haven't had a leak since.

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thecantaloupeman

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deve05 said:
Had the same problem on my 84 when I bought it and it was due to corrosion on the tank neck. I removed the hose and used a cutting wheel fitted with a metallic brush and polished the neck. I used a rolled up paper towel stuffed into the neck to prevent debris from getting in and a vacuum cleaner to suck out the debris and paper towel after cleaning.

I then cleaned out the interior of the hose with 620 grit sand paper about as far back as the neck will go. I treated the neck with aircraft alodine sealer to prevent future corrosion and reinstalled the hose and put in a new clamp.

This was 4 years ago and haven't had a leak since.

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So how is it that the corrosion makes a leak? Is it because the rust bubbles and breaks the seal or something?

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Snoots

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Seen it before. You can clean the area and try JB Weld or, drain the tank, drop it, and take it to a radiator shop and have them re-sweat the seal.

Since it's a '78 I'd have them clean it out while there and you can install a new intake sock and level seal.
 
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Get some idea what it's gonna cost, may be cheaper to get a new tank
 
deve05

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thecantaloupeman said:
So how is it that the corrosion makes a leak? Is it because the rust bubbles and breaks the seal or something?

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The corrosion makes a leak because corrosion doesn't appear evenly. It lifts up the seal in some areas and not others and holes are created where gas can leak out. Keep in mind that while the truck is moving there's a lot of fuel in there slushing back and forth. Especially on a full tank.

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thecantaloupeman

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idahovette said:
Get some idea what it's gonna cost, may be cheaper to get a new tank
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Well is it possible I could just clean the nipple myself like the first guy mentioned? Or is that not enough. His idea seemed easy enough to do.
 
Snoots

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If you do:

BRASS BRUSH.

Not metal.
 
thecantaloupeman

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Snoots said:
If you do:

BRASS BRUSH.

Not metal.
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Is that because it will make sparks? Could i just do it by hand instead of with an angle grinder?
 
Snoots

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I'd still use brass. It ain't worth the risk.
 
thecantaloupeman

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Snoots said:
I'd still use brass. It ain't worth the risk.
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Is it better to do this by hand or use a Dremel/angle grinder or something?

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gotyourgoat

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Why not just take metal out of the equation and use a 3m style scrubbing pad?
 
SquareRoot

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Metal. By the time you get out of the hospital, the new tank should arrive.
 
Jrgunn5150

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Lol, tanks are cheap. If I go to the effort to drop one, I replace it.
 
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