# Plastic fuel tank leak



## Paul40

I just bought a White Yardboss GT1650. It has a plastic fuel tank that leaked at the fuel outlet when I bought it. Turns out someone had used a metal tire valve stem for an outlet. I replaced the valve stem with a brass fitting that fit quite tightly into the plastic hole and sealed it with automotive GOOP, both inside and outside the tank. It held for about a week, but today noticed that the gas had disolved the GOOP. Anyone out there have any ideas? I'm not sure what kind of plastic the tank is made of, or if there is such a thing as a cement that adheres to the plastic without being eaten up by the gas.

'55 MH 55, '08 Craftsman DYS 5500, White Yardboss GT1650, Gilson CV8


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## farmertim

Hi Paul,
a good two part epoxy putty should fix the hole/crack and not be dissolved something like "devcon" if you have that stuff there.
Cheers


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## Oldchevysguy

Interestingly, the best, permanent repair that I've experienced is cutting a one gallon milk jug into 1/2" strips and 'carefully' melting them into the suspect areas. The area must be thoroughly cleaned and wiped down with denatured alcohol (or Isopropyl alcohol).

I have done two plastic diesel tanks. One repair is over 5 years ago and still leak free.


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## Mickey

Think you'll find most fuel tanks are made from Polyethylene. Down at the molecular level PE is just a very high density paraffin wax. (speaking from an ME's experience designing a lot of plastic parts) It's hard to find anything in the way of "glue" that will stick permanently. Along the line of what oldchevyguy suggested is plastic welding. That's where you apply a melted filler of the same material to the intended joint.

Harbor Freight offers several different low cost products and filler rods that just might fit the bill. Was in to HF a few days ago and I think I remember seeing one of these welders on sale.

Search results for: 'plastic welder'

Another low cost approach is to thread a screw into the hole and include an o'ring under the screw head. Best to use a self tapping screw with a washer head.


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## Paul40

Thanks for the info and suggestions. I'm going to be doing some experimenting with the epoxy and the "welding" with the plastic bottle. The fitting I used actually cut a thread into the plastic, but the plastic is quite thin, no heavier than maybe 15-20 mil, so can't get much of a thread going. I also tried making a nut out of a coupling so I could tighten it up from inside the tank, but the tapered thread pretty much ruled that out. Just couldn't tighten it with the limited access. I'd put the GOOP around the fitting in an effort to reinforce it. I agree that the plastic is likely polyethylene, and that there is nothing I'm aware of that will stick to it well. Might have to break tradition and take it to a pro. Drats!!

Happy tractoring!


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## Country Boy

I use a product called "Seal All" at work to seal up the occasional gas tank. It is gas and oil resistant, and some of the carburetor manufacturers recommend using it for sealing up welsch plugs in their carbs. Comes in a tube much like Goop. Its a contact cement and sealant. Its in a yellow tube.

Seal-All Adhesive Product Information


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## jhngardner367

Go to the local motorcycle shop,and buy one of the metal valve-stem kits for tubless tires.They have a flat end,and 2 neoprene washers,a flat washer,and a hex nut.They are easy to put into the tanks,with a neoprene washer on each side of the hole,just put on the flat washer,and tighten the nut.I've done this for several years,and haven't had any trouble with leakage. Just remember to take out the valve core .


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## ErnieS

I used JB Weld on a plastic tank and it held pretty well. If you spread a fair layer at your crack and pull a vacuum on it for a minute or 2 and then a couple pounds of pressure, what happens is you pull the stuff in and then flatten the stuff that makes it inside, locking it in place.
My repair lasted a year until I gave the mower to the new owners when I sold the place in Florida.


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## wjjones

Oldchevysguy said:


> Interestingly, the best, permanent repair that I've experienced is cutting a one gallon milk jug into 1/2" strips and 'carefully' melting them into the suspect areas. The area must be thoroughly cleaned and wiped down with denatured alcohol (or Isopropyl alcohol).
> 
> I have done two plastic diesel tanks. One repair is over 5 years ago and still leak free.



That is a good idea i need to repair a tank leak as well, and plan to try that..


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