1950s Have NEVER seen this before!

[Jon S]

I filled the tank for the winter last November and drove the car 1 mile to the house. The car has been sitting in the garage since then. Today I smelled gasoline in the garage and took the vented cap off and saw gasoline dripping out of the filler pipe. I did not overfill the tank in November and had to siphon a lot out to stop the leaking. I tried to attach a video or picture with no success. It is up to the top and dripping. What could be causing this???

[Clewisiii]

Gasoline can absorb water from the air. Does your tank have an open to air vent. And has it been humid.

[Jon S]

Picture:

Gasoline can absorb water from the air. Does your tank have an open to air vent. And has it been humid.

Interesting- the Ethanol laden gasoline is known for absorbing water - never thought of that. I believe my 1958 has an open to air vent

[The Tassie Devil(le)]

Your tank is vented, both at the filler neck (see the little indent on the rim) ans a full tank that was filled up in the winter, will expand the contents as the outside weather warms up.

This can create a problem like you say.

I have always been told that if one completely fills a tank, then one needs to go for a reasonable drive to get the full level down a bit to stop what you encountered.

If you ever fill up a Jerry Can and let it stand for a time, when you go to release the cap, there will always be a pressure-relief then the seal is loosened.

Bruce.

[Jon S]

Thanks Bruce. Never has happened before.

[Jon S]

I took the gas cap off the Cadillac this morning and looked with a flashlight. Where I could see gasoline 3/4 of the way down the filler pipe last night the pipe is totally dry so I guess with the cold weather the gas has receded back into the tank.

[Lexi]

Jon, rather than having to start your car during the winter to burn some gas off, I can think of an alternative. There are a number of gasoline siphon/extracation tools available. The best would probably be one of those straight siphon tubes that are equipped with a copper manifold that is loaded with a ball bearing. You simply insert the flexible clear tube into the gas filler neck and push it down into the fuel. Then vigoresly shake the tube up and down which creates a temporary vacuum leading to a pressure differential at either end of the line. This triggers the the flow of gas through the tube. The secret behind this tool is that it is in reality a self priming pump, (caused by your shaking the line). Have it empty into a suitable container with enough room to accept the flow of fuel. Once it begins it flows quite fast, and you can stop shaking the tube and let it continue to siphon on it's own. This way, you don't get a mouthful of gasoline (as that technique is not required here), and you don't have to start your car in the frigid cold. Not good for our aging engines. Should probably add this to the tools we never heard of thread that TJ started. Clay/Lexi

[Eric DeVirgilis CLC# 8621]

Plain gasoline will do the same thing with respect to temperature changes.

[tcom2027]

Kinda begs the question, why fill the tank all the way up the filler neck?

Air space or head space as it's known in industries using or transporting liquids, especially light fuel, headspace in a container, whether a fixed tank or a tank trailer is beyond critical.

Additionally tanks that have liquid drawn from then have to be vented or the negative pressure created by the pump drawing the liquid out (bladder tanks excepted.) will collapse the tank.

To expand on Tassies' comment, I have a couple of plastic gas containers. I overfill them a lot when I am going to use the fuel immediately. I remember filling them early one morning with the idea of filling my tractor as soon as I got home. One thing led to another and I didn't get around to it until mid afternoon. Temp had climbed from about forty five (F) to seventy five or so. THey were sitting in the sun in the back of my pickup the entire time. When I finally got around to fueling the machine the containes looked like they were about to give birth. I gingerly loosened the vent caps on two of them. Whooosh! I had left the cap loose on the third container, so no worries.

Many cars from the time frame we are discussing have vent tubes running alongside or in the filler tube which vents the tank. If one of the openings of the tube is blocked by fuel,the tank can't vent properly. Packards' design whistled as the tank filled. When the whistling stopped the tank was full. Che'cool

If the filler neck is completely filled in normal operation the expansion wouldn't have much effect as enough fuel would be drawn off to uncover the vent tube very quickly.

In states that require vapor recovery nozzles it's not a problem as the automatic shutoff pretty much takes care of the overfilling problem. As an aside,in our modern cars it's important not to top off the tanks as regularly overfilling can have deleterious effect on the vapor recovery system, mainly the filter causing the CEL to be lit. Depending on the model, it can be an expensive repair.

Obvious solution, don't overfill the tank or if you,do drive around a little. With the rate of fuel burn on cars of the era we are discussing it doesn't take very many miles to empty the filler neck. We live seven miles from a town of any appreciable size and there is a short six percent pitch on the way. I use the fuel stop in town. We drive our old cars on the top half of the tanks so when it's lay up time they all have at least a half a tank of fuel. Never had a fuel quality related problem in thirty years of owning collector cars.

tony.