Older international dump with fuel tank problem venting

[john510]

I have a older 1983 international Dump with a cummins 300 big cam and it has square fuel tanks

I noticed that no matter how full the fuel tanks are they seem to seep a little out by the cap.
it almost like its venting steam back into the tank and causing pressure out even though I have a vent in the tank

Whats causing the steam effect back in to the tank? Im sure its the return line but why the steam effect and how to stop it?

 

[2xR]

I've never seen a truck that wouldn't puke a little fuel from around the cap when it was full of fuel, and, sloshin' down the road. Guys with the shiny tanks don't completely fill up so they won't ride down the road with fuel streaked on the tanks.

If yours is really, really, bad you may need to replace the fuel cap gasket, or, you may want to try only filling to about 80% capacity.

 

[Racer X 69]

The "steam" is fuel vapor. Any fuel that does not get used by the engine is bypased back to the tanks, and it gets heated up by the engine, hence the "steam".

And 2xR is right about the seepage. No matter how tight you screw the caps down, they will always leak a bit. On the square tanks the threads are pipe thread, and the only way to completely seal them is with pipe dope, and you don't want to do that, you would need a pipe wrench to get the caps off each time you fuel.

 

[mechman]

You do need to make sure the vents are actually clear - they can plug up over time. You need to check them, not assume. Also, the caps shouldn't leak, if the gasket is good unless you filled the tank too full. Tanks are only meant to be filled at 80% capacity - that's about 4 inches or more below the top.

 

[pop]

check the vent like mechman said & the hose coming off them. check the cap some older trucks had vented caps.