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Old 20-10-2007, 22:10   #1
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Gas tank leak around sendeing unit gasket

Hi everyone, I have a gas leak in my inboard gas tank around the rubber seal that came with the new sending unit. I installed it 2 years ago. I first tried the gasket sealer(name escpes me at the moment), it its brown and sticky and comes in a round jar and has a brush built into the jar cap. That was last year but that didn't work all too well. As I discovered today, gasoline is an excellent solvent for that gasket material. It was nice because I was able to just clean off all the sticky stuff with just gasoline. I also have permatex 1 and permatex 2 onboard. I guess one is fast drying and one is slow drying. But does anyone know what is the actual stuff that should be used. The problem is that if I fill the tank I get a gas leak.
thanks,
Petar
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Old 21-10-2007, 01:46   #2
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A Silicon Gasket product will work fine. I don't know what Permatex is, but if it say's it is OK with Fuel, then go for it.
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Old 21-10-2007, 03:06   #3
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Polyurethane (3M 5200) & Polysulphide (3M 101) sealants are both compatible with Gasoline, but generally Silicone is not recommended.

Permatex has several products, sold for gas tank repair, including:
Instant Gas Tank Repair #12020
Goto: http://www.permatex.com/documents/td...tive/12020.pdf

See also: Tanks A Lot, Part 3: The epoxy "cure" ~ by Norman Ralph
”One of the most annoying problems that can occur on a sailboat is a leak in the diesel fuel tank. If you don't have the time, expertise, or courage to attempt to repair it yourself, you can always arrange to have your boatyard repair it. But you can do it yourself, if you are willing to try...”
Goto: Good Old Boat magazine: Volume 2, Number 1, January/February 1999
Good Old Boat: Tanks A Lot, Part 3 by Norman Ralph

O-Ring Materials Compatible with Gasoline, Automotive
eFunda: O-Ring Materials Compatibile with Chemical Gasoline, Automative
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Old 21-10-2007, 04:14   #4
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Permatex 1 & 2 are basically the same but one drys hard and the other is supposed to stay playable. I've used both between cork gaskets on diesel tanks with good results.
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Old 21-10-2007, 08:46   #5
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pirate NEVER EVER USE SILICON without thought

When you put silicon or any other wet gasket in your fuel line you are asking for trouble.,always make a gasket if you cant obtain original spare,,most sender units come with new gasket,when you use wet gasket ,as you push ba pins through holes into tank a small piece of gasket material sticks to end of pin,now go sailing,swish swash,round balls gets washed off end of pin and guess where its going,staight to filter housing intake,whoops no fuel....when motor stops and pump no longer sucking fuel,this material miraculously springs out of housing inlet and causes much head scratching..but you can guarantee next time you start motor pick up pipe will do just that !!!
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Old 21-10-2007, 19:52   #6
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Quote:
Originally Posted by Fasttimes View Post
When you put silicon or any other wet gasket in your fuel line you are asking for trouble.,always make a gasket if you cant obtain original spare,,most sender units come with new gasket,when you use wet gasket ,as you push ba pins through holes into tank a small piece of gasket material sticks to end of pin,now go sailing,swish swash,round balls gets washed off end of pin and guess where its going,staight to filter housing intake,whoops no fuel....when motor stops and pump no longer sucking fuel,this material miraculously springs out of housing inlet and causes much head scratching..but you can guarantee next time you start motor pick up pipe will do just that !!!
Never---ever use silicone with fuel----diesel will cause it to "filament" is the best word I can think of

Also when you installed the sending unit did you use the screws that came with it? Each one should have a small washer/gasket on it...otherwise the fuel will migrate up the threads.
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Old 21-10-2007, 20:26   #7
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How is the sending unit installed? Is it a plastic tank? I just went through a similar problem. If you have a setup where the sending unit is attached by 5 screws tapped in to a plastic tank, I can probably help you out.
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Old 22-10-2007, 19:09   #8
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Hi everyone again, few facts I didn't specify. I have atomic 4 gasoline engine, and gasoline disolves the permatex 1 and 2 like it was meant to be a slovent for cleaning permatex. Tank is aluminum, and there are 5 SS self tapping screwes going through the gasket material and into the aluminum tank. The sending unit did not come with screws. The leak is not at the gasket. Its through the hole that self tapping screws go through and the gas comes out at the top around the screws.
I used the boatlife plysulfide quickdrying caulk and put it only on each screw(a generous amount). That worked. Unfortunately there seemed to be a problem in the contacts at the terminals of the sending unit on the inside of the tank . So after fixing the leak I didn't have a correct measurement. I had an open circuit at the terminal. I spent another day pulling everything apart and this time around I made sure that fuel gauge shows the entire range on the scale as I move the float up and down.
I put the caulk again and the stuff is drying out.
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Old 22-10-2007, 19:29   #9
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Good Luck.
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Old 23-10-2007, 03:08   #10
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Quote:
Originally Posted by phorvati View Post
... I used the boatlife plysulfide quickdrying caulk and put it only on each screw(a generous amount). That worked. Unfortunately there seemed to be a problem in the contacts at the terminals of the sending unit on the inside of the tank . So after fixing the leak I didn't have a correct measurement. I had an open circuit at the terminal ...
Your have a case grounded (1 wire) fuel gauge, which utilizes the metallic connection between the sender body screws and the tank as a negative return. As you indicated, the sealant isolated the sender from the gauge, so you had an open circuit , which should indicate a full tank.

See also Testing Engine Gauges:
1. http://www.cruisersforum.com/gallery...=500&userid=79
2. http://www.cruisersforum.com/gallery...=500&userid=79
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Old 23-10-2007, 09:14   #11
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Sounds like you might try larger self tapping screw(s) to get a metal to metal seal.

You might try pop rivets (the ones that have a water tight cap).

Or if the calk works you might have to run a ground line from the sender to the tank or boat ground.

Or you could get a new sender that has a wired ground.
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Old 26-10-2007, 08:40   #12
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I think its done. I just filled the tank to the deck fill and no leaks. My sender has a wired ground, but like I said the problem was in the connector on the inside. Anyhow thanks everyone,
Petar
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Old 26-10-2007, 10:25   #13
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I have used the aviation grade Permatex to seal up the diesel tank access ports on an aluminum vessel with rubber gaskets.

I'm glad thing worked out Petar.
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