gas filler cap leaks

[BluTrukker]

My 68 has a new gas tank in the factory location(PO installed). The problem I have is gas leaks out any time I make a right hand turn with more than a half tank of gas. The cap is pretty new. it also looks like the PO used a file to smooth out the very top of the neck, maybe that is causing it, I don't know. Is there any type of gas cap that can correct this? Possibly one that fits down inside the neck and expands?

[elektrik]

Originally Posted by BluTrukker

My 68 has a new gas tank in the factory location(PO installed). The problem I have is gas leaks out any time I make a right hand turn with more than a half tank of gas. The cap is pretty new. it also looks like the PO used a file to smooth out the very top of the neck, maybe that is causing it, I don't know. Is there any type of gas cap that can correct this? Possibly one that fits down inside the neck and expands?

I recently had the exact same problem-I swapped out my old gas tank for a new one (in fact, I haven't even gotten rid of the old one-still in the garage, )...

Anyways, I was leaking gas all over my new paint job-was getting pissed; however, the way I ended up fixing it was by troubleshooting a (seemingly) unrelated problem-I had a new tank, sending unit and locking gas cap but my gas gauge wasn't "working". I also noticed when I removed my gas cap that all these fumes and pressure would release from the tank, and that my gauge would work (temporarily)

The solution (for me anyways): I took the gas cap (it was plastic), found the smallest drill bit I could find, and drilled a miniature hole in my gas cap-that relieved the pressure, made my gauge work and stopped the spillage (because the cap could seal correctly)...

[68jimmy]

Originally Posted by BluTrukker

My 68 has a new gas tank in the factory location(PO installed). The problem I have is gas leaks out any time I make a right hand turn with more than a half tank of gas. The cap is pretty new. it also looks like the PO used a file to smooth out the very top of the neck, maybe that is causing it, I don't know. Is there any type of gas cap that can correct this? Possibly one that fits down inside the neck and expands?

Go to your favorite auto parts and ask for a stant non-locking vented gas cap for a 67-70. The one I picked up is chrome non-locking and looks original. It has a thick rubber o-ring and is very snug as you twist it on, I no longer have issues with leaks when turning or any pressure buildup. I was using a locking stant cap previously...

good luck.

[El Jay]

I don't know the part#, but I got locking caps from my local CarQuest store.
Haven't had a more problems with leakage on either truck.

[Brad]

In the past I've just used compressed cardboard- like what's used for gaskets- that I had laying around and made 2 donuts and added them to the rubber. It helped seal the filler tube.

[68c10guy]

is the gas cap supposed to be vented?

[HoupPhotography]

Originally Posted by 68c10guy

is the gas cap supposed to be vented?

That's a good question, mine isn't. I had the same problem, gas spilling out of the filler neck... I looked at my gas cap and the rubber was deteriorated in some area's, bought a new one at checker and the problem went away.

If your adding anything to the filler cap, it's the wrong one. Thre are a few that look the same, the difference is the inner cylinder. Be POSITIVE that the one you have is correct for your application.

[Sicmaro]

the tanks should be vented...... mine did the same thing, I just re-bent the lip of the filler neck where the cap locks onto it and it holds the cap tighter and no leaks.

[68jimmy]

Originally Posted by 68c10guy

is the gas cap supposed to be vented?

Not sure if it was 71 or 72 when the tank came with a vent as part of the fuel sending unit or not... But I do know that my 68 requires a vented cap otherwise it build all sorts of pressure especially now that the weather is warming up.

[prg machine]

Originally Posted by 68jimmy

Go to your favorite auto parts and ask for a stant non-locking vented gas cap for a 67-70. The one I picked up is chrome non-locking and looks original. It has a thick rubber o-ring and is very snug as you twist it on, I no longer have issues with leaks when turning or any pressure buildup. I was using a locking stant cap previously...

good luck.

Is "stant" a brand name?

[BluTrukker]

I was wondering if "stant"is a brand or he meant "standard". Anyway I plan on stopping in to the parts store next week, so I will check.

[BluTrukker]

68jimmy, do you have a pic of the cap so I know what it looks like?

[prg machine]

Originally Posted by BluTrukker

I was wondering if "stant"is a brand or he meant "standard". Anyway I plan on stopping in to the parts store next week, so I will check.

I wonder what it is?

[Sinister]

Originally Posted by prg machine

Is "stant" a brand name?

Stant is a brand name...

[elektrik]

Originally Posted by Sicmaro

the tanks should be vented...... mine did the same thing, I just re-bent the lip of the filler neck where the cap locks onto it and it holds the cap tighter and no leaks.

That's why I just drilled a tiny little hole in my gas cap, because I figured it was a *cheaper* fix than modifying my gas tank =]

[Longhorn Man]

stant p/n 11623 for 67 - 70.

[BluTrukker]

Thank you very much everyone.

[prg machine]

Originally Posted by Longhorn Man

stant p/n 11623 for 67 - 70.

who sell dat??????????????

[Longhorn Man]

I know advance auto does... with stant being the biggest name in thermostats... I'm willing to bet any parts house can get it, or cross reference the number at least. But that's a good number. I've held onto it after getting one for my first truck, then second and third, and I've lost a cap, had one stollen (with the fuel) ran over one... and managed to wear a couple out.

[rwgregory]

I have a Stant locking cap on my '67 GMC. The cap used to fit loosly on the filler neck when installed and would spew fuel out whenever turning right at anything above a crawl. I got 3 large O-rings at the parts store and put them over the snout of the gas cap. Now the cap fits snugly up against the lip of the filler neck, still breathes, and only spits out a drop or two of fuel when turning right.

[68jimmy]

Originally Posted by BluTrukker

68jimmy, do you have a pic of the cap so I know what it looks like?

Here is a link with a picture...

http://www.partsamerica.com/ProductD...rtNumber=11623

[eightbanger]

I decided to buy a new cap from Classic Parts as the old one was loose and had some paper wraped around to try and make a better seal by the PO but the new Stant one did not fit the neck, so I thought I had choose the wrong year or maybe it was for a stepside, so got another and made sure this time, but it was the same as the last one...now i've added an extra rubber washer to the origianal and it's fine.

[72-c20]

Originally Posted by 68jimmy

Not sure if it was 71 or 72 when the tank came with a vent as part of the fuel sending unit or not... But I do know that my 68 requires a vented cap otherwise it build all sorts of pressure especially now that the weather is warming up.

my 72 K20 did not have any vent fittings in the tank, and just one fitting on the sending unit.... no charcoal venting in the engine bay either....

according to some stuff I've been reading the the vents were not put on the 20-30 series trucks (some GVW cut-off)...

I replaced my tank with a '72 style tank, and a new cap, and I capped all the vent fittings on the tank, but my old vented cap does not fit the filler neck at all.

not sure if my new cap is going to cause a problem or not.... I don't think it's vented....