Fuel Tank Leaking from Sending Unit

[JoLin]

Bit of an oddball problem. I have a 16' Sylvan with a poly-something, below deck 24 gallon tank. The deck above the tank sagged over time and eventually created a slight 'bow' in the tank itself. I get some fuel leakage from the sending unit because the flange is sitting on a slightly concave surface.

I fixed the deck and I'm looking for a solution to the leakage short of replacing the tank (short and simple- I don't want to shell out the bucks). Thinking that a double gasket and Permatex 85420 (Permashield fuel resistant) gasket dressing might do the trick.

Any thoughts on that, or other ideas? The boat's in Florida (I'm in New York) and I want to have a plan of attack when I go down there in November. I do plan to pull the tank out and have it cleaned as there's junk in it I haven't been able to get rid of.

 

[tpenfield]

Even a single gasket with the permatex may do the trick. I am thinking the bowing of the tank broke the seal that the original gasket had.

 

[GA_Boater]

The pressure from the deck on the sender may have compressed the gasket and now a fresh gasket will probably fix you up. It can't hurt to double up the gasket.

I would use the Permatex between the gaskets to stick them together and none on the tank/sender sides in case the sender needs removal in the future.

 

[smokeonthewater]

Bow the sending unit plate to fit the tank

 

[JoLin]

Bow the sending unit plate to fit the tank

Possible, but if I remember correctly the flange is pretty thick and the bow would have to be very slight. When I'm down there I have to work on the boat in the open, without any access to the garage and tools (like a bench vise) that I have at home. It's tough to 'finesse' stuff

Sounds like I'm on the right track with new (maybe doubled) gasket and sealant. Personal experience tells me it oughta work, but sometimes you guys come up with weird and wonderful new ways of doing things

 

[smokeonthewater]

A block of wood with a bow cut in it along with a hammer and 2x4...
Can be notched on site with cordless tools as needed would make short work of the metal work.

I would shy away from trying to use gaskets or sealer to mate poor fitting parts especially on such a critical system as fuel.

I strongly suggest either making the plastic fit the metal or making the metal fit the plastic.... The latter is likely easier.

You COULD buy a new sender and then build your shaping jig at home. Then simply work it to fit on location.

I suspect that you would dont it VERY east to bend the sender plate once set up.

 

[smokeonthewater]

One more option would be two heavy aluminum or stainless backer plates inside the tank... Each a half circle with holes drilled and tapped... Each would require one extra hole outside the sender diameter to fasten it to the tank....
Then bolts through sender could be tightened down enough to flatten plastic flange.

 

[JoLin]

A block of wood with a bow in it is a possibility. Thanks for the suggestion.

I've thought before of a backing plate, but the tank plastic is thick and very stiff. It assumed the concave 'set' over who knows how many years. It won't be drawn back into place easily. The plate has to be narrow enough to fit through the hole. So, unless the plate is very thick, I think it will bend before the tank does. I don't have the equipment to work with heavy gauge metals, even at home.

 

[thumpar]

How much access do you have to the tank? Any chance it could "pop" the bow out of it. Kind of like paintless dent removal.

 

[Grub54891]

I myself shy away from double gaskets on anything. 2 gaskets has a chance of blowing one out. You could make a single gasket with thicker material, and a bit of sealer would be better. If possible you could make a backer out of aluminum, oval shaped to fit through the hole, and a round topplate to fit the sender. The best cure, and safest is a new tank.

 

[JoLin]

The best cure, and safest is a new tank.

At over $500. for the replacement I'll try some other option(s) first.

For those concerned with the safety aspect, let's remember that the sender is at the the very top of the tank and the fuel is not pressurized. A gasket won't 'blow out.' and suddenly flood the boat with fuel. Whether it's a single gasket with sealant, a double gasket with sealant, or a bowed sending unit flange with a gasket... it's only the weight of fuel against it when the boat is bow high, that I need to be concerned about. Right now I get fuel seepage and fumes at the sender. I need to eliminate them.

Whichever option I choose will either seal it or it won't. I'll know soon after I try it.

Thanks for all the advice, guys!

 

[JoLin]

How much access do you have to the tank? Any chance it could "pop" the bow out of it. Kind of like paintless dent removal.

Afraid not. The plastic has taken a set that can't be corrected without somehow re-forming the top of the tank. Heat might do it, but now we're talking about a process that's beyond me and my Harbor Freight heat gun . I also don't know if there are internal baffles that have also become misshapen over time.

 

[Fed]

Don't forget the gaskets and/or sealant under the screw heads, they're just as important as the main gasket.

 

[Grub54891]

Agreed, there is little pressure on the sender itself. I just don't like doubled up gaskets to Bandai anything. Now if it is just seepage, a single gasket, and sealer would probably do the trick.

 

[smokeonthewater]

Keep that heat gun away from the boat!

Honestly it likely WOULD do the trick but I HIGHLY doubt that it is ignition protected....

You would have to fill the tank close to full with water to safely use it and also be sure you had fully ventilated any fumes...

I know you didn't say you were gonna use it but just figured the potential danger made it worth discussing just in case.

Now a good industrial steam source might be just the trick... Have de-icing equipment in the trunk??? Lol

 

[JoLin]

Never had any intention, Kevin. I should have added a line about me and my $9.99 heat gun potentially disappearing in a mushroom cloud....

 

[smokeonthewater]

I was 99.999% sure you wouldn't but....

Mushroom clouds are bad umkay.