The Stovebolt Site Forums The Shop Area General Truck Talk Gas expansion

51, 3/4 ton, 235, new gas tank, I have filled the tank with gas in the cool of the morning, parked in front of the house. The truck is sitting at a slight angle against the curb. The day has heated up and the truck is in the sun, gas starts leaking out from the filler cap. I did not top off at the gas station. The immediate fix I did was to pull that side of truck up on to the curb, no leak. What is going on and what can keep this from happening. Different kind of gas cap????

happens to us all, just hafta live with it - you listed the exact reasons it happens, just filled tank warms up with truck leaning to the filler side, so you know what to avoid, no way to prevent liquid expanding with temp

Bill

I never fill my Harley for the same reason. Even on a cool day like today (mid 40's) it seems to expand and dump two gallons on the ground.

An unvented gas cap would create a different problem if you did change out the vented one to stop the gas from leaking out. An unvented cap would create a vacuum in the fuel system, eventually resulting in fuel starvation issues.

These vehicles were built before automatic nozzles. An experienced filling station hand could hear when the tank was approaching full and he quit filling. With today's automatic nozzles, it is possible to overfill them. Next time you fill it, watch the gauge and quit when it shows full.

Yes, older style nozzles were longer, went further down the filler. I think I will try and develope my ear to the noise of gas coming up the filler. Probably have to hold back the seal on the nozzle though. Many thanks

Didn't the old nozzles produce a whistle that stopped when it was getting full? I don't have problems from expansion because I always listen for the noise in the pipe. The only problem I have is trying to hear when someone has a radio blaring away.

The old nozzles weren't built with a whistle, but there was a change in tone when the tank neared full. Some cars had a loud whistle, but it was from the shape of the fill pipe.

I listen for the change in noise also.I don't fill the tank when I know I'm going park soon after

I wondered where the sound used to come from in the good old days! My 38 Master which I would imagine is similar to the truck, doesn't have the little air bleed passage in the filler like my 51 GMC does. I am wondering if it will be a little trickier to fill up when I use it some day.

There are some of the old ones that were a bear to fill with an automatic nozzle. We got the automatics in the early 60's. I don't remember the specific models that would keep tripping the nozzles.

When I fill my '38 coupe I fill at the low speed setting on the nozzle. If I use the fast setting it will sometimes splash some out when it shuts off. When it shuts off I stop filling (no rounding to the next dollar or even the next quarter) to keep from over filling. The only issue I've had with gas dripping past the cap was this fall on the VCCA tour when we parked in one lot on an extreme angle.