The Stovebolt Site Forums The Shop Area General Truck Talk Why does gas seem to be reproducing in my tank??!!

Ok, so I fill up completely at the station this morning and drive home, a few hours later, i come outside and gasoline has leaked out of the cap and down the side of the truck, making the paint bubble up as it went. So I open the gas cap, and the gas starts pouring out onto the ground, probably a cup came out, then i jumped on my back bumper a bit to shake some more out so when i made a turn or something it wouldnt just leak out again (I need a new cap). Anywhoo, i scrape off all the paint and put some rustoleum on it about 20 minutes ago, go outside to put on a coat of paint just about 5 minutes ago and gas is dripping back out of the cap, i unscrew the cap and the gas level is back to where it was at first, brimming at the rim! Why the hell is there more gasoline in my tank now than was 20 minutes ago, I havent done a thing to it!

this used to happen on a crappy dodge i used to have years ago. i think the gas expands then it heats up. it's cooler in the ground and when it sat in the sun for a while it would run out. i used to avoid topping it off. just don't go out for a cig. by the door.

Gas is stored under ground where it is cool, and in quantity. Then you take it out of the ground and put it in your itty bitty tank, in the warm (hot) air. Like most every thing it expands when the temperature rises.

LG

i meant to say it expands when it heats up, not then it heats up.

That's basically what it is. From now on, don't fill the tank completely full.

yer complainin about the tank filling itself for free? get out the gas can and start collecting it!

most of these ol trucks do that, park in a different spot so the filler is uphill, and as said, never try to top it right up, stop as soon as the nozzle first kicks off

Bill

My 52 did it too.
I'd only fill it up all the way if I was going to be driving a long distance right then.

Before I figured it out I'd fill up, get home, then later smell gas and have to go repark it on the side of a hill. By the morning it would cool off and I'd be fine on the way to school.

Grigg

Thanks for the info guys, I thought there might have been a racoon in there.

OK guys, I just deleted 2 joke posts. Let's remember this forum is for serious truck talk. The jokes go in the Greasy Spoon.

Thanks.

I uh... fill mine up my '65 c10 all the time, I've never had this issue since I bought it in 2003.

I also went to the hardware store and bought a BIG rubber washer from the plumbing section to fit onto my gas cap, as the paper/cardboard whatever that is was worn out. That might have something to do with it.

-W

update: after thinking on it some more... maybe I did have this issue when I first got my truck... but not since I put the big rubber O-ring on the gas cap there. The cap fits more snugly as well.

hardware store/plumbing department... take the cap with you.

The expansion factor is why I like to buy fuel in the morning on road trips. It does expand a little more than 1% with the temperature difference. Depending on the tank volume will depend on the amount expanded, however, 17 gallons of fuel would expand to about 2 1/2 cups worth.

If you do top it off to the bottom of the filler cap, then I would recommend driving the truck a bit to use up a bit of fuel.

I also suggest you look at the cap like Woogeroo mentioned as your seal may be gone.

Yeah that's what just happened to me and my '58. Just don't top off during the warm days.I was surprised that the overflow tube doesn't get it and just siphon it on to the ground as opposed to down the paint ? Why is the over flow not working ?

Overflow tube?? No overflow tube on these old trucks. What you see is the vent tube, doesn't go outside.
I have had this happen to me as well, new cap, so the gasket was good. Best bet is not to fill it up that far.

Gasoline has a thermal expansion rate that is over 4.5 times that of water! That is why the problem seems so dramatic. Gas expands a lot.

You could always add an overflow tube to the filler neck: Remove the neck, add an overflow tube, reinstall the neck and pipe the overflow out of the cab

Or just don't fill it up all the way.

As a kid, on the farm, I used to be assigned the task of filling up the old mans '72 Chevy C20 with gas when he got home from work. I got to where I could tell by the sound when the gas got to the filler neck it was time to stop.

If I overfilled it I got a boot to the butt! Ahh the art of positive reinforcement. It's an aquired skill.

John

perhaps your tank is venting else where.it has to vent somehere. is your cap vented..If it wasn't vented as as your pump removes the fuel, i8f it wasn't vented it would create a vacuum that could suck in your tank
ron

happened to me, a little bit, when i first bought my 57.
i am always use to topping off all my vehicles, but from then on, in my 57, when i feel i am getting close to full, and can actually hear it start to gurgle in the tank, i stop, and dont fill it all the way.
hasnt overflown out my cap since then.

leonard