Gas Tank Leaking After Filling - Around Filler Neck Grommet

[BrokenHero]

Hey guys -

I've read the other similar threads but the issue seems to vary from car to car. So here's my scenario - any help is appreciated!

I have a recently installed, brand new gas tank.

I've been driving the car fairly regularly with no issue in the gas tank department. Filling it all the way, etc

Today, after driving in about 10-15 miles, then parking it for a few hours at a park, I decided to top off the last 3-5 gallons at the gas station. My gas gauge never goes above half and used to be fully broken so I err on the side of having a full tank. I also have some Sta-Bil in there.

Immediate after filling it up, the gas tank starts to leak at the station. I drive home. It's still leaking. I'm freaking out, thinking all 19 gallons are going to flow out of this tank in my apartment's parking garage.

I finally find the area that's dripping and put a pot under it. I wipe up the gas on the concrete. I send a video to my mechanic friend. He says it seems to be coming from the neck grommet so once the gas goes below that point it will
stop leaking. Good thing the leak isn't at the very bottom of the gas tank.  Over the next few hours the pot only gets like half full so the problem doesn't seem super urgent anymore.

That said, it's still dripping and I'd like to know if this is just a function of filling the gas tank up too much (although, I have done this with no issue recently), if the gas tank was installed incorrectly, if I need to just move the grommet down, if the filler neck is in disrepair, and why we this might have happened all of a sudden.

Another thread mentioned the rubber vent hose and I'm not sure how to check if that's functioning properly.

I am doing some trunk repair, and have a decent amount of cleaning products and heavy stuff back there. Perhaps something was shifted or jarred out of place recently?

Is this fixable myself or bring to a mechanic? Thanks!

Ted

[Kern Dog]

How old is that grommet? Maybe it has shrunk over time and even split?

[70 sublime]

Do you have the small breather tube on the back side of the filler neck pipe ?

[Wingnut426]

Did you pop the gas cap to see if the tank was pressurized?

[BrokenHero]

Thanks all

- the grommet actually looks pretty new. Doesn't look crusted, very black, not gray or brittle looking. I assume it was put in when they installed the gas tank a year or so ago. I could be wrong though.

- I do have the small metal breather tube behind main tube. Pic attached.

- I popped the gas cap to fuel the car and another few times during the process of collecting the leaking gas, but didn't notice it was pressurized and it didn't do anything noticeable at all.

Thanks!

[RiverRaider]

It could have been a new but old stock grommet or a cheap one.  I have seen ethanol and other fuel additives eat up those before. 
Any chance ethanol in your fuel? 

[JR]

My money is on a bad grommet. Maybe it was cracked or split when the tube was inserted.

I'd also blow out that vent tube with an air hose when you drop the tank just to be safe.

[JerseyJoe]

My car is doing exactly this.
It's the filler neck where it enters the tank, if it was from the vent it would be leaking from the frame rail.
The repro grommets are probably just okay with a perfectly round surface but they are thin at the opening and can tear or deteriorate quickly. I'd bet your filler tube is pitted (like mine) just past that original undercoating, allowing the gas to get by. New filler tubes are $70 from Vans Auto.
There's probably some low-buck "fixes" but doing it right is probably best with gasoline  

[BrokenHero]

Thanks for the help, everyone!

Yeah, JerseyJoe, I'm guessing it's the filler neck. Good call on doing it right when it comes to gasoline.

Have you installed your new filler neck yet? I was thinking of ordering one along with a grommet to be safe and hiring a local shop to install it, just to be smart. I don't have a ton of tools and space right now.

[JerseyJoe]

Haven't done it yet, I just spent a bunch on engine goodies. But it's not a tough job at all.
There's three screws for the cap, 3 screws for the tube, and 4 screws for the rubber floor seal.

[BrokenHero]

Sounds good, thanks!