Re: Leaking gas cap

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Posted by deanostoybox on January 05, 2021 at 19:58:11 [URL] [DELETE] :

In Reply to: Leaking gas cap posted by DAN on January 05, 2021 at 19:11:27:

A non vented gas cap will seal. The problem with a non vented cap is that bugs like to seal the vent that that the gas tank has in the center on top. One fellow drilled a hole in the hood to make the vent hole accessible.
My 8N came with one of those "safety" caps that is supposed to keep the gas from leaking out if the tractor were to turn upside down. It has 4 holes on top and extends about 4" into the tank. One warm December day I was pulling a truck bed with a chain to knock down some weeds. Had a couple of weeks of cold weather so gas was winter blend, but it was 85 and bright sunshine that day. Tank was at about 8 gallons and there is no battery door on the tractor. I kept feeling something cold and wet hitting me in the face but saw nothing coming out of the radiator. Then it happened again when I turned and the light was right, I could see gas spraying out of the holes on the top of the gas cap. Bought a vented cap like used on the NAA and hundred series. It would leak going up hill or when taking off from a stop sign with the tank over 1/2 full. Bought a non vented cap and it sealed up real well. Had put it on when hot in the late morning, was working on another tractor late evening and it was cooling down. Heard a metallic thunk coming from my tractor. Went over and opened the gas cap and sure enough could here it sucking air when I did. Put the vented cap back on and ran it that way never filling the tank more than half until the time came to remove the hood again. Then I cleaned out the bug nest from the tank vent and soldered a piece of 1/4 fuel line over the hole and to the top of the tank bringing the other end to near the back of the tank where I changed over to 1/4 rubber fuel line, then down if front of the battery where it changes back to another steel fuel line which is tucked behind the starter. It has a 1/8 pipe nipple soldered to the end and screwed onto that is a "dope smoking pipe" bowl which has a screen inside and a cover with a "flame hole" in it. Put the non vented cap back on and good to go - for about six times putting gas. Then that cap started to leak as the brass spring material that holds down the seal was made from cheap material and had lost it's tension. So I dug around in the junk and found an old vented cap from some truck or something. It had a worn out cardboard seal. I welded up the vent hole and put the rubber seal from the new but defective on the old truck cap to replace the worn out cardboard one, put a thick O ring behind it to provide the necessary pressure for the seal and have been running that way for almost 4 years with no problems. If the tank were to puke some gas out the vent it would go on the ground, not on top of the hot engine or exhaust manifold or electricals. Bugs cannot get past the creen and if some dauber should plug the flame hole it is readily accessible under the starter. that has not happened yet.

When Ford came out with the NAA series the went to a vented cap but put it in the middle of the tank so that gas sloshing around or going up or down a hill would not leak out of the vent in the cap. Based on my own observations it seems that the amount of gas that leaks is small and with a hot engine and the fan blowing air back there that most of he gas will evaporate before it becomes noticeable. I think most folks have a battery door so may be unaware that the gas cap leaks a bit under certain conditions, hence the often made recomendation to use a vented cap when the tank vent gets plugged.

As to non vented caps, the one that NAPA sells (Sparex) is sure pretty, but that is what I had that lasted 6 fills then started to leak. If you can find a non vented cap of good quality and keep the tank vent hole open you wil be able to solve that problem.

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