Fuel tank mystery leak

[VFRhugh]

Anyone ever had a fuel tank leak under the cowl band? I thought it was coming from the cap but disproved that today. Only noticeable after filling up. Only leaks while driving. There is an annoying noise from the tank when less than half full at certain rpms. The next obvious step would be to look under the band but I thought I'd ask first. Not sure how to remove and not destroy something.
Hugh

[Gary WA]

could the neck where cap is screwed on be loose sloshing around? neck attached to tank area.

[VFRhugh]

The blue in my fist pic is a paper towel I taped to the tank to see if the filler neck or cap was leaking. It's dry around the filler area. I don't see how it doesn't leak unless I'm driving.
Still confused,
Hugh

[H. L. Chauvin]

Hi Hugh,

While driving, fuel may possibly slosh around and exit a small opening in the upper part of the fuel tank. So many Model A's were worked on by non-mechanics, absolutely nothing appears amazing anymore.

Maybe try:

1. Having someone place and holding down about (5) sheet layers of paper towels where you suspect fuel may be exiting.

2. Then back up very slowly & hit the brakes and check the towels for leaks.

3. Then, if no leaks, go forward very slowly and hit the brakes again to try to make the opening leak on the paper towels ... and again, check the towels for leaks.

4. Then is no leaks, shake car left to right and repeat test.

Please let us know.

[DaWizard]

Ya know, if this was me, I would be pulling off the cowl strip to see if the tank isn't cracked under it. Only has 2 nuts holding it down, but yea, it is behind interior kick panel.

Since you have already placed the towels down around the filler and that doesn't seem to be leaking.

Anyway you look at it, I foresee the tank coming off to repair it properly.

Just my 2¢ worth

[Benson]

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Originally Posted by VFRhugh

Anyone ever had a fuel tank leak under the cowl band? I thought it was coming from the cap but disproved that today. Only noticeable after filling up. Only leaks while driving. There is an annoying noise from the tank when less than half full at certain rpms. The next obvious step would be to look under the band but I thought I'd ask first. Not sure how to remove and not destroy something.
Hugh

Looks like the rear hood bracket is fastened down with a Phillips head screw. Ford never used them.

Maybe the screw is a self tapping screw and is too long and has penetrated the gas tank?

[DaWizard]

Hey, just had a brain fart and had to stink up the place with my escaping thoughts.

Do you own one of these http://modelafuelneck.com/, and if so, have you been using it and setting the filler nozzle to "auto" and taking your hands off it?

If you can answer Yes to both of these questions, then I am putting my money on a cracked filler neck where it meets the tank.

Now, you ask how I came up with this, well, I'll tell ya. The tank is not welded or affixed to the "cowl" where comes up through the cowl hole, and I can see the added weight of the "EPA certified filler hose handle/nozzle" adding a stress where the tank and the neck attach that Henry never even dreamed about, and unless you stand and support the added extra weight of the hose and nozzle, that weight is bending the tank at the joint where the two pieces come together. Do this a few times, and you have a flexed crack, just like breaking the pull tab off a can of your favorite liquid drink, or like removing the lid from a can of creamed corn once you have run the can opener around 98% of the way.

Just HAD to stink up the place with that brain fart.

[Steve Plucker]

Unless you are Superman and have x-ray vision, I would remove the hood and cowl band and more than likely that will show your problem.

The electronic weld, where you can see the little ripples, may have cracked thus your leak.

As it is now...you are fighting the situation.

Pluck

[1931 flamingo]

When you fill up, how full??
Is there not a gasket on the gas cap?? Rattle: look in the tank at the float mechanism, is it rubbing on a baffle?? What year/model is this??
Paul in CT

[VFRhugh]

Cowl band removal is next. I need to get over the fact that it's not leaking unless driving. Also inside the car is completely dry. Photo is what it looks like when gas is visible outside. The hood support bracket screws aren't hitting anything. Who knows why there are extra holes in each side of the bracket screws. Anyway thanks for the interest,
Hugh

[C26Pinelake]

Originally Posted by DaWizard

Hey, just had a brain fart and had to stink up the place with my escaping thoughts.

Do you own one of these http://modelafuelneck.com/, and if so, have you been using it and setting the filler nozzle to "auto" and taking your hands off it?

If you can answer Yes to both of these questions, then I am putting my money on a cracked filler neck where it meets the tank.

Now, you ask how I came up with this, well, I'll tell ya. The tank is not welded or affixed to the "cowl" where comes up through the cowl hole, and I can see the added weight of the "EPA certified filler hose handle/nozzle" adding a stress where the tank and the neck attach that Henry never even dreamed about, and unless you stand and support the added extra weight of the hose and nozzle, that weight is bending the tank at the joint where the two pieces come together. Do this a few times, and you have a flexed crack, just like breaking the pull tab off a can of your favorite liquid drink, or like removing the lid from a can of creamed corn once you have run the can opener around 98% of the way.

Just HAD to stink up the place with that brain fart.

You sure like the crass words like fart.

[Gary WA]

under side seam may have come apart also?

[Gary WA]

Originally Posted by VFRhugh

Cowl band removal is next. I need to get over the fact that it's not leaking unless driving. Also inside the car is completely dry. Photo is what it looks like when gas is visible outside. The hood support bracket screws aren't hitting anything. Who knows why there are extra holes in each side of the bracket screws. Anyway thanks for the interest,
Hugh

Are those two holes your leak??

[H. L. Chauvin]

Hi Hugh,

You're doing great in investigating.

It is not much different from repairing a metal roof leak .... search & investigate for the "source" of the leak .... hole, seam, joint, whatever? ....... then look at options for repair.

Metal water bucket leak or metal gas can leak is not much different either ...... investigate "source"!

Best of luck.

[VFRhugh]

Gary,
At first I didn't think so but if driving creates a low pressure area at this spot that could explain being dry inside the car. There is a little shoulder that might prevent fuel running back in. Removing the cowl band next. If nothing obvious will try very low pressure and soapy water. Great pictures by the way.
Will post when leak is found,
Hugh

[Big hammer]

I sealed up my gas tank, double gasket under gas cap and adapted an air fitting to the outlet with an air gauge and shut off vavle. Then I pressurized the tank at a low pressure, it held pressure for several hours confirming no leaks around gas gauge,etc!
You could use a pressure regulator to keep a constant pressure, and then you could spray a soapy mixture to find your leak! I think I kept the pressure about 20 psi !
My brothers dropped an out board motor and put a big dent in the tank :-( I used shop air pressure with a rag in the fill hole and blew the tank until the dent popped out :-)

[Y-Blockhead]

Hugh, may I suggest you try some fluorescent dye? I have found numerous evasive leaks using this dye and a ultraviolet light.

https://www.amazon.com/Interdynamics...W6ARDZGN5WQQZH

[Tom Wesenberg]

20 pounds pressure on the tank would likely bulge the tank. I wouldn't dare use more than one or two pounds. Multiply that by the square inches of surface area of just the top of the tank, and you have a lot of pressure trying to deform the tank.

[tbirdtbird]

"Maybe the screw is a self tapping screw and is too long and has penetrated the gas tank?"

That screw is beyond the pinch weld

[Mitch//pa]

Since you already know u have a leak I think you can find it without pressurizing