gas cap leak - The 1947 - Present Chevrolet & GMC Truck Message Board Network

shelby987 · 01-05-2006, 06:10 PM

ok.....so gas is at $2.40 a gallon, and everytime I fill my tank I figure I splash/slosh at least $1.50 all over the side of the truck. I tried taking a large O-ring, cutting it down the center, and using it as a make shift gasket, but it doesn't seem to seal correctly, and without that spacer, the cap and the cardboard gasket are even worse.....any suggestions?

Yes, I have tried not filling it to the top, I never use the automatic fill on the pump, but I only have the 16 gallon tank in the cab.....and only filling it half way full everytime isn't really an option.

ChevLoRay · 01-05-2006, 06:31 PM

I misunderstood his problem. So, I'm deleting my comment. Thanks, guys.

alf1096 · 01-05-2006, 06:37 PM

he is talking about after he fills up and the gas sloshes out of the tank then you are driving, not while filling up. Maybe try a different gas cap.

Longhorn Man · 01-05-2006, 07:08 PM

Any parts store will have them in chrome for you for less than 10 bucks.

powder2 · 01-05-2006, 07:14 PM

there is a papeer gasket on the gas cap get another one and put with the origanal one it will solve your problem it worked for me someone off of here told me to try it

Longhorn Man · 01-05-2006, 07:24 PM

All mine have had a thick rubber flat gasket.

1978steven · 01-05-2006, 08:42 PM

I had the same problem with my 71'. Got tired of it, and bought a new cap with new seals on it at Auto Zone. Problem solved.

**Green Machine** · 01-05-2006, 09:05 PM

Got a NAPA nearby ? Stock shelf item usually. Don't expect it to last forever though, 2-3 years and you may need a new one when the gaskets wear out.

**Stocker** · 01-05-2006, 11:01 PM

Ditto Green's NAPA advice, though I typically get a lot more than 2 to 3 years out of 'em!

RJ100 · 01-05-2006, 11:30 PM

If you dont want to change caps , get a piece or cork gasket material and make a new gasket. It worked fine for me.

Fred T · 01-06-2006, 12:42 AM

Go to the parts store and get a new cap. They are now unvented (by law) and the gas doesn't slosh out.

**Green Machine** · 01-06-2006, 01:14 AM

Well, not to be picky, but they do have a spring loaded vent that lets air into the tank as the gas gets used up else you would pull a vacuum in the tank and the truck would stall out. The vent and seal however are meant to keep the gas and vapors in and some pressure can build up in the tank. I still don't fill mine to the top because it doesn't seem 100 pecent tight. Also check the fill neck over real good, they can get bunged up over the years, straighten and bend as needed to get the cap to sit tight as possible.

shelby987 · 01-06-2006, 08:57 AM

So the rubber gasket can't be purchased seperately?
I know my father has a 55 chevy, and he had to get the guy behind the counter to go through 10 different gas caps before he found one that fit right...figured this wasn't going to be an off the shelf item.
No on the napa by the way....autozone carry this perhaps?

chevyfarmer · 01-06-2006, 09:15 AM

I have had this problem before on different trucks, and the double cork gasket has worked on all of them except one. I put a tank in a 67 and the cap leaked, tried several things including a new cap but it still leaked. Finally I discovered that the tank had been in a truck that was in an accident and it had actually damaged the surface where the gasket should seal. It was bent, not allowing it to seal. Might want to check that as well.

Longhorn Man · 01-06-2006, 09:36 AM

Auto zone maybe, I know for a facr advance auto has them on hand. I used to have the number here for the cap, but it'd disapeared on me. They have always had them in stock every time I went for one. It is still vented, I think fred's reference are to 71 and newer, which, by law, can not be vented (emissions regulations that started in 71)

**pjmoreland** · 01-06-2006, 03:37 PM

The Stant 10623 is what I used to buy for my '67. I'd have to buy a new one about every 2-3 years because the rubber seal would crack.

I have found that when I'm twisting my gas cap on, it gets tighter as I'm turning it, and then at the end it gets loose. If I don't quite tighten it on all the way and stop turning it before it starts getting loose, it seals better.

Longhorn Man · 01-06-2006, 03:40 PM

That may be the one I am thinking of.. smooth chrome with the sticker in the center? (peel it off and use carb cleaner to remove the glue0
My olf GMC was like that with the twisting, but the one ton isn't. I dunno WHY some trucks are like that, but it is worth paying attention to if your cap pukes down the side.

BowTieMan · 01-06-2006, 06:21 PM

I went to autozone and they looked u the number on the computer and mine seals good.

And why is it at some gas stations when you fill it, it doesn't shut off and it pours out?

shelby987 · 01-07-2006, 09:44 AM

thanks everyone, I went to advanced and they had it....the guy behind the counter seemed very concerned that the engine and drivetrain questions were answered correctly after I told him it shouildn't matter........so I did a test, and a gas cap for a 70 2wd half ton with a 350 is an acceptible replacement for an original gas cap on a 70 4wd with an I6!
Anyway....$4.xx and it works like a charm.....filled it to the neck, drove down the worst dirt road around and no gas residue on the bed whatsoever!

**truckdude239** · 01-07-2006, 10:05 AM

Quote:

Originally Posted by BowTieMan

I went to autozone and they looked u the number on the computer and mine seals good.

And why is it at some gas stations when you fill it, it doesn't shut off and it pours out?

i have yet to have a gas sations handle to cut off filling up my truck i normally just put 25 buxs in it and its full i've always tought it was beacause the tanks are different then new tanks

76bonanza · 01-07-2006, 11:57 AM

Mine always shuts off on my 68 with original tank on my 76 it would never shut off.

01-05-2006, 06:10 PM	#1
shelby987 Registered User Join Date: Mar 2005 Location: Just outside Durham, NC Posts: 894	gas cap leak ok.....so gas is at $2.40 a gallon, and everytime I fill my tank I figure I splash/slosh at least $1.50 all over the side of the truck. I tried taking a large O-ring, cutting it down the center, and using it as a make shift gasket, but it doesn't seem to seal correctly, and without that spacer, the cap and the cardboard gasket are even worse.....any suggestions? Yes, I have tried not filling it to the top, I never use the automatic fill on the pump, but I only have the 16 gallon tank in the cab.....and only filling it half way full everytime isn't really an option. __________________ 1969 SS 350 Camaro Sold 2008 1970 3/4T K20, stock height with 33's, 250 I6, 3 on the tree, and locked front and rear 4.10's 1980 Chevy Malibu 2 dr Sold 2007 1993 Olds. Cutlass Ciera Wagon Traded 2006 2003 Saturn L200 w/5pd. D/D My list spans 5 decades with One common thread.....GM!

01-05-2006, 06:31 PM	#2
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Re: gas cap leak I misunderstood his problem. So, I'm deleting my comment. Thanks, guys. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was. Last edited by ChevLoRay; 01-06-2006 at 12:03 PM.

01-05-2006, 06:37 PM	#3
alf1096 Registered User Join Date: Aug 2005 Location: Texas Posts: 124	Re: gas cap leak he is talking about after he fills up and the gas sloshes out of the tank then you are driving, not while filling up. Maybe try a different gas cap. __________________ 1970 Short Stepside----Process of Restoring 1983 1/2 Silverado

01-05-2006, 07:08 PM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: gas cap leak Any parts store will have them in chrome for you for less than 10 bucks.

01-05-2006, 07:14 PM	#5
powder2 Registered User Join Date: Oct 2003 Location: Abilene Texas Posts: 287	Re: gas cap leak there is a papeer gasket on the gas cap get another one and put with the origanal one it will solve your problem it worked for me someone off of here told me to try it

01-05-2006, 07:24 PM	#6
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: gas cap leak All mine have had a thick rubber flat gasket.

01-05-2006, 08:42 PM	#7
1978steven Registered User Join Date: Oct 2004 Location: Currently New Windsor, NY but Texas is home Posts: 332	Re: gas cap leak I had the same problem with my 71'. Got tired of it, and bought a new cap with new seals on it at Auto Zone. Problem solved. __________________ 2002 Silverado 2500HD LB7 CCSB LT EFI Live by Rob at ATP, Edge CTS Insight DSP 5 control, S&B CAI, PPE boost valve, Pro Fab AIH, AirDog II 165, PPE WIF sensor delete plug, 5" stainless exhaust, Cognito braces & HD tie rods, H2's 315/70 R17 BFG's 2004 Tahoe LT 2006 Silverado Z71 LS 1971 Chevy C10

01-05-2006, 09:05 PM	#8
Green Machine Senior Member Join Date: Jul 2004 Location: Estherville, Iowa Posts: 3,371	Re: gas cap leak Got a NAPA nearby ? Stock shelf item usually. Don't expect it to last forever though, 2-3 years and you may need a new one when the gaskets wear out. __________________ 1968 C10 307 3spd Long Fleet ------ http://67-72chevytrucks.com/vboard/s...d.php?t=201103 1970 C10 305 Super T10 Long Fleet --- http://67-72chevytrucks.com/vboard/s...d.php?t=202285 1971 C20 383 TH350 Dana Posi ----- http://67-72chevytrucks.com/vboard/s...d.php?t=206894 2001 GMC Sierra 1500 C3 6.0

01-05-2006, 11:01 PM	#9
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,595	Re: gas cap leak Ditto Green's NAPA advice, though I typically get a lot more than 2 to 3 years out of 'em! __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

01-05-2006, 11:30 PM	#10
RJ100 Registered User Join Date: May 2005 Location: roanoke wv Posts: 60	Re: gas cap leak If you dont want to change caps , get a piece or cork gasket material and make a new gasket. It worked fine for me.

01-06-2006, 12:42 AM	#11
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Re: gas cap leak Go to the parts store and get a new cap. They are now unvented (by law) and the gas doesn't slosh out. __________________ Fred There is no such thing as too much cam...just not enough engine.

01-06-2006, 01:14 AM	#12
Green Machine Senior Member Join Date: Jul 2004 Location: Estherville, Iowa Posts: 3,371	Re: gas cap leak Well, not to be picky, but they do have a spring loaded vent that lets air into the tank as the gas gets used up else you would pull a vacuum in the tank and the truck would stall out. The vent and seal however are meant to keep the gas and vapors in and some pressure can build up in the tank. I still don't fill mine to the top because it doesn't seem 100 pecent tight. Also check the fill neck over real good, they can get bunged up over the years, straighten and bend as needed to get the cap to sit tight as possible. __________________ 1968 C10 307 3spd Long Fleet ------ http://67-72chevytrucks.com/vboard/s...d.php?t=201103 1970 C10 305 Super T10 Long Fleet --- http://67-72chevytrucks.com/vboard/s...d.php?t=202285 1971 C20 383 TH350 Dana Posi ----- http://67-72chevytrucks.com/vboard/s...d.php?t=206894 2001 GMC Sierra 1500 C3 6.0

01-06-2006, 08:57 AM	#13
shelby987 Registered User Join Date: Mar 2005 Location: Just outside Durham, NC Posts: 894	Re: gas cap leak So the rubber gasket can't be purchased seperately? I know my father has a 55 chevy, and he had to get the guy behind the counter to go through 10 different gas caps before he found one that fit right...figured this wasn't going to be an off the shelf item. No on the napa by the way....autozone carry this perhaps? __________________ 1969 SS 350 Camaro Sold 2008 1970 3/4T K20, stock height with 33's, 250 I6, 3 on the tree, and locked front and rear 4.10's 1980 Chevy Malibu 2 dr Sold 2007 1993 Olds. Cutlass Ciera Wagon Traded 2006 2003 Saturn L200 w/5pd. D/D My list spans 5 decades with One common thread.....GM!

01-06-2006, 09:15 AM	#14
chevyfarmer Registered User Join Date: Feb 2005 Location: Owosso, Mi Posts: 242	Re: gas cap leak I have had this problem before on different trucks, and the double cork gasket has worked on all of them except one. I put a tank in a 67 and the cap leaked, tried several things including a new cap but it still leaked. Finally I discovered that the tank had been in a truck that was in an accident and it had actually damaged the surface where the gasket should seal. It was bent, not allowing it to seal. Might want to check that as well. __________________ 67 short wide 355ci 3 on tree 69 short wide 250ci 3 on tree 68 long wide 283 3 on tree 72 2wd Blazer project 454 5 speed

01-06-2006, 09:36 AM	#15
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: gas cap leak Auto zone maybe, I know for a facr advance auto has them on hand. I used to have the number here for the cap, but it'd disapeared on me. They have always had them in stock every time I went for one. It is still vented, I think fred's reference are to 71 and newer, which, by law, can not be vented (emissions regulations that started in 71)



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01-06-2006, 03:37 PM	#16
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,426	Re: gas cap leak The Stant 10623 is what I used to buy for my '67. I'd have to buy a new one about every 2-3 years because the rubber seal would crack. I have found that when I'm twisting my gas cap on, it gets tighter as I'm turning it, and then at the end it gets loose. If I don't quite tighten it on all the way and stop turning it before it starts getting loose, it seals better.

01-06-2006, 03:40 PM	#17
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: gas cap leak That may be the one I am thinking of.. smooth chrome with the sticker in the center? (peel it off and use carb cleaner to remove the glue0 My olf GMC was like that with the twisting, but the one ton isn't. I dunno WHY some trucks are like that, but it is worth paying attention to if your cap pukes down the side.

01-06-2006, 06:21 PM	#18
BowTieMan Registered User Join Date: Dec 2003 Location: Glendale Arizona Posts: 747	Re: gas cap leak I went to autozone and they looked u the number on the computer and mine seals good. And why is it at some gas stations when you fill it, it doesn't shut off and it pours out? __________________ "A true hotrodder wouldn't be content untill he had created a car so violent, so hairy, so totally sick that the very act of dropping the hammer would result in instant death. Anything less results in the need to go faster." - Tony DeFeo

01-07-2006, 09:44 AM	#19
shelby987 Registered User Join Date: Mar 2005 Location: Just outside Durham, NC Posts: 894	Re: gas cap leak thanks everyone, I went to advanced and they had it....the guy behind the counter seemed very concerned that the engine and drivetrain questions were answered correctly after I told him it shouildn't matter........so I did a test, and a gas cap for a 70 2wd half ton with a 350 is an acceptible replacement for an original gas cap on a 70 4wd with an I6! Anyway....$4.xx and it works like a charm.....filled it to the neck, drove down the worst dirt road around and no gas residue on the bed whatsoever! __________________ 1969 SS 350 Camaro Sold 2008 1970 3/4T K20, stock height with 33's, 250 I6, 3 on the tree, and locked front and rear 4.10's 1980 Chevy Malibu 2 dr Sold 2007 1993 Olds. Cutlass Ciera Wagon Traded 2006 2003 Saturn L200 w/5pd. D/D My list spans 5 decades with One common thread.....GM! Last edited by shelby987; 01-07-2006 at 09:44 AM.

01-07-2006, 11:57 AM	#21
76bonanza Senior Member Join Date: Mar 2003 Location: St robert Mo Posts: 2,001	Re: gas cap leak Mine always shuts off on my 68 with original tank on my 76 it would never shut off. __________________ 1968 c10 lowered 3" 4" 355/Th400 built by Hatfield racing in joplin MO

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