C1 Gas Tank Venting Question

[Bob B.]

Hi all,

Recently, I had parked after driving my 1960 with a full tank and gas began dribbling out from around the cap. It is a non-vented cap and maybe the seal isn't hermetic, but there is a vent hose from the top of the tank. It seems that with a vent at the top of the tank there shouldn't be any buildup of either pressure or vacuum in the tank. I have also had a vacuum build up before and hear a hiss when the cap is removed. Others tell me that their tank also has the vacuum hiss when the cap is removed. Am I misunderstanding something about function of the vent tube, or does it sound like my vent tube is clogged?

Thanks,

Bob

[William C.]

Re: C1 Gas Tank Venting Question

Sounds like the tube is clogged.

[John H.]

Re: C1 Gas Tank Venting Question

Bob -

Sounds like you should remove the tank cover panel and check out the condition of the vent hose; with that configuration, you shouldn't have any pressure buildup in the tank.

[Gary Bishop]

Re: C1 Gas Tank Venting Question

My first incident with this problem on our `62 was on a National Road tour in 1990. I lost about a quarter tank of gas before I knew it. Thanks to running a CB at the time, other Members were aware of the problem and had me stop and open the gas filler cap. It stopped the siphon affect from the over filling of the tank.
It has happened once or twice since then if I do over fill the tank.
I put on a new tube for venting but it still happens once in a while.

[Jack H.]

On straight axle cars...

the gas tank received a built-in venting feature circa 11/15/56. That removed the burden of figuring out which type of gas cap to use (vented or sealed).

BUT, since the filler neck on SA cars rises ABOVE the tank to the filler door, it's NOT a good idea to 'top off' the tank so much that you're carrying fuel in the filler neck! Even with a vented tank system, you need SOME room inside the tank to absorb normal expansion of the fuel due to ambient temperature.

My advice is to stop putting gas in the tank when the pump's automatic shut off valve kicks in....

[Verle R.]

Re: On SOLID axle cars...

I agree with Jack about the SOLID axle cars.

It is a good idea to stop when it clicks off.

One time I topped off the tank on a hot day and went inside the building. Cool gasoline expands when it warms up. When I came out there was a solid stream of gas from the overflow hose and a large, spreading pool under the car.

Not a good thing!

When I hear "straight axle" I think of the front beam axle of 20's & 30's cars.

Verle