: Gas tank hissing -- B Body



hueterm
06-23-10, 01:48 PM
This is re: one of my RM Wagons, not a FWB -- but does anyone know why there is a hissing noise from the gas tank when I go to fill up? My RM Sedan did the same thing, so I don't think it's vehicle specific...

It's usually when I'm pretty low on fuel, and when the weather is hot.

Sometimes it hisses forever. If there's that much pressure in the tank, spitting on it the wrong way looks like it would cause it to explode....much less a wreck...

I can't find a fully vented cap, only one with a vent button -- any ideas?

77CDV
06-23-10, 01:53 PM
It's venting. If I run my two newer cars low on gas in hot weather, when I go to fill up, I have to release the cap slowly to allow the pressure to escape. There's something about it in the owner's manual IIRC.

hueterm
06-23-10, 02:01 PM
So if I get a vented gas cap, will that make the check engine light come on?

Stingroo
06-23-10, 02:02 PM
Not sure, mine does this too. I thought it was normal.

It vented for awhile the first time I filled it, but I ran it down pretty much alllll the way to the E (poor college student life :thumbsup:)

hueterm
06-23-10, 02:08 PM
You need something to make the fumes reconstitute into gasoline so you can drive further ;-)

HUF
06-23-10, 03:03 PM
Mine does it too regardless every time I refill.

Stingroo
06-23-10, 03:24 PM
You need something to make the fumes reconstitute into gasoline so you can drive further ;-)

LOL if only...

mjs182004
06-23-10, 03:27 PM
Both of my cars do it, and many friends cars do it. so I always thought it was normal.

The-Dullahan
06-23-10, 04:28 PM
I have to release the cap slowly to allow the pressure to escape.

This is bringing back memories of Steam-Powered transportation. Wish I had a garage, I'd build a new one.

As for the hissing, it is fairly normal, from what I have heard, though I have never driven a car that DID that, I have heard it and heard ABOUT it from a number of people. It seems to be most prevalent on semi-new cars. from the early 2000's, though that probably has nothing to do with it and I've heard about it on cars quite a bit older.

I drive around all day in my big, black box in direct FL sun and don't have that happen. the Position of the gas cap (Directly behind the bumper) may have something to do with this though.

Benzilla
06-23-10, 04:30 PM
All of mine do it. But only of it's really low.

77CDV
06-23-10, 08:42 PM
So if I get a vented gas cap, will that make the check engine light come on?

Probably.

Aron9000
06-23-10, 09:30 PM
I wouldn't worry about it. My 1991 does that, in fact if its really hot and low, you can feel a little bit of pressure push on the cap when you take it off.

JimMLINY
06-24-10, 11:21 PM
with called it, "running on fumes", vented cap or not when the tank is low and you go to fill er up, a hiss is what you hear especially in da summer months, totally normal.

Now if you hear a hiss when you are changing out snow tires for summer tires in spring and are underneath the jacked car just checking out underbody brake lines and such that is another usually expensive story!