I just took ownership of this 08 H2 and the 2 times I filled it up with gas (till it was full) I smell gas for just a few gallons. Maybe 1/8th tank is consumed and then it goes away.

So after today's fill up I climb under there and look all around the tank and I see no signs of leakage at the filler hose or any where on top that I can see. Granted I can't see much with it mounted.

But then I see a couple of moist little spots towards the front of the tank by two holes in the tank cover. So there's either a hole in the tank way up high such that it only leaks when it's very full or one of the connections on top is leaking.

There are no drops of gas coming from the tank just the smell and a little gas moisture spot towards the front of the cover plate.

What's the common knowledge on this? Is it usually a hole in the take or one of the connections to the tank? The pump looks try all around it so I don't think it's that.

 

I got to crawling around and found a moist stain at the top of the tank around a blue plug at the front. I circled it in red. You can see there is another one of these plugs at the back which is circled blue. Does anyone know what this is?

 

I think it's called a fuel tank vent valve. I was able to get a better look with more light. The rear one has a hose that just presses on (has ****** fitting but no clamp) and the hose runs up the filler hose. So I guess that's a vent line.

The front one (circled in red) has the same hose and looks the same but I cannot tell where the hose. It actually looks to be routed towards the front.

So I think it's one of these, but the one on the H2 is blue and looks more round on top.

 

I went to the dealership and they said it's not a serviceable item and the whole tank would need to be replaced. This seems like total bunk. Oh and I believe it's called a rollover valve and they are on nearly every silverado, etc. But it is strange I cannot find anything about anyone else having issues with it.

 

Sorry I can't be of any help but if you figure something out let us know. May need help with this in the future.

 

I think I'm going to try some fuel resistant epoxy to seal around the valve. Permatex 85420 seems like a good candidate but I've never used it and need to learn more.

 

Just to update this thread, I used Permatex Motoseal Ultimate Gasket Maker around the smelly vent valve. I didn't have to lower the tank, I just used a mirror to see on top of the tank. I also put a hose clamp around the press-on hose just in case that wasn't sealing either.

Probably a dozen fill-ups later and no more gas smell. Success.

 

Good job! Cheap and easy are the best fixes.

 

I had the same issues on two vehicles in the past. One was a split vent line near the filler neck; the other was where the fuel pump and filter unit mounted to the tank.

The PO of my 2 had the fuel pump unit replaced for leaking and odors before I bought it. It's an '04. Hopefully you got yours fixed.