Hot Rods Fuel leaking out of tank overflow / vent line

I just installed a Tanks fuel tank in the 31 Model A Sedan under the back window, the vent tube is ran down thru the floor to the outside but seems to be leaking. Is this ran incorrectly and needs to be above the tank or do I have to much hose that it is acting as a syphon?

Thanks for any advice, Kerwin

 

The vent tube needs to run up and above the tank in a loop before it runs down to the ground otherwise fuel will slosh around and leak like there's no tomorrow. You may need to place an additional vent away from filler side of tank. In my 35 phaeton I ran the vent from the tank up through floor to the belt line in a loop and then back down through floor exiting at the rear near the chassis, tank and fender. Too hard to pull trim off to photograph however 15yrs now since built and still no issues.

 

mgtumpy has it right, up with a loop in it.
I also put a pcv valve.
in the end for safety purpose- like a roll over.

 

Thanks guys, that helps a lot!

 

I'm wondering if that will also apply to this type of rollover vent valve. Installed in the top of my RPU gas tank there is no way I will be able to have a loop higher than the valve as the top of the tank is practically even with the top of the bed. .

 

And obviously no one has a clue to this one.
I'm thinking that since it has a check ball that will close when the fuel level is high then it will only vent when required and will not siphon because of the check ball rollover design.
That's my theory and I'm sticking to it.

 

If the check ball is steel it won't be floating.
If you can get one that is straight then you could put a loop in the hose on the way back down.

 

This problem has reared it’s ugly head again now that I’m installing my vent/ rollover valve for the final time.

My valve does in fact have a separate phenolic plastic ball above the steel ball.

The plastic ball floats when the tank is full and stops fuel.

As the tank needs air it will breathe.

The steel ball is of course for rollover shut off.

This info is from the maker of the valve, Tanks.

I’m still not sure if I’m going to have issues with any fuel smell or where to route the vent given thephysical limitations of my tanks location in the bed of my RPU.

 

Change your truck theme too moonshine and run a copper tubing like they do in the stills or like you can do for brake lines at the m/c.

 

Kerwin, Were you able to fix the problem? I’m having the same issue. Wondering if my vented cap is not venting. It only does it when I fill the tank full.

 

I use aluminum tubing for vent tubes as it's super easy to bend tight and I always bend a loop before heading down. If I can't do the loop above the tank I do it as close to the top as possible. Sometimes I use a 90 degree fitting out of the vent tube, then the loop behind the tank, and then down. I always put a PCV valve on the end of the tube just to avoid fuel spills and keep bugs from trying to crawl up an open tube.