1972 Gas tank

[Jim Gagliardi]

My 72 had a tank replacement somewhere along the line. When I fill the
tank I get some leakage which seems to be from the top of the tank. I was
told that there is some type of vent or valve on top of the tank that was
prone to leaking. The guy I talked to said to epoxy it shut. Is there such
a thing? I could not find anything in my shop or assy. manual.

Thanks, Jim

[Jeff Chester]

Re: 1972 Gas tank

Here's my best theory on what to do... And old nice 72, with gas tank problems.
Please replace the tank, and sending unit.. I've seen too many fire balls.....
of after maths of them....
jc

[Jeff Chester]

Re: 1972 Gas tank

Here's my best theory on what to do... And old nice 72, with gas tank problems.
Please replace the tank, and sending unit.. I've seen too many fire balls.....
of after maths of them....
jc

[Joe L.]

Re: 1972 Gas tank

Jim------

There is a pressure-vacuum valve on the top surface of the tank, about 6 inches to the left of the filler opening. Most of the valve is internal to the tank and the entire assembly is soldered into the tank. This valve first appeared on late 1969 tanks and continued through 1974. This valve is required if, (a) you are going to use the non-vented fuel cap used for all 70-74 Corvettes and, (b) you're evaporative emissions control (EEC) system is to function properly.

The pressure vacuum valve is, as far as I know, not serviced seperately (I KNOW for sure that it was never available from GM). I would not recommend sealing it. Instead, I'd recommend replacing the fuel tank.

[Joe L.]

Re: 1972 Gas tank

Jim------

There is a pressure-vacuum valve on the top surface of the tank, about 6 inches to the left of the filler opening. Most of the valve is internal to the tank and the entire assembly is soldered into the tank. This valve first appeared on late 1969 tanks and continued through 1974. This valve is required if, (a) you are going to use the non-vented fuel cap used for all 70-74 Corvettes and, (b) you're evaporative emissions control (EEC) system is to function properly.

The pressure vacuum valve is, as far as I know, not serviced seperately (I KNOW for sure that it was never available from GM). I would not recommend sealing it. Instead, I'd recommend replacing the fuel tank.

[George C.]

Re: 1972 Gas tank

Replace the tank, that's your best bet.

[George C.]

Re: 1972 Gas tank

Replace the tank, that's your best bet.

[Jim T.]

Re: 1972 Gas tank

Jim I would also check the filler neck gasket. If you would remove the gas lid assembly, and clean the water catcher of dirt, remove the gas cap, them remove the water catcher. If the water catcher is old you could use some vasoline or something similiar to ease the removal over the filler neck. Now you can examine the area around the filler neck and see it could be leaking. Joe Lucia has done a post on this a couple times about a gasket material that is superior to the original cork gasket. I am not sure that the original gasket is still available from GM. You can also see some the top of the tank and the valve mentioned is to the left of the filler neck, perhaps with good lighting you could examine this.
Another area that could be leaking is where the return hose connects to the right side of the top of the tank. This is a difficult area to access but warrants checking.

[Jim T.]

Re: 1972 Gas tank

Jim I would also check the filler neck gasket. If you would remove the gas lid assembly, and clean the water catcher of dirt, remove the gas cap, them remove the water catcher. If the water catcher is old you could use some vasoline or something similiar to ease the removal over the filler neck. Now you can examine the area around the filler neck and see it could be leaking. Joe Lucia has done a post on this a couple times about a gasket material that is superior to the original cork gasket. I am not sure that the original gasket is still available from GM. You can also see some the top of the tank and the valve mentioned is to the left of the filler neck, perhaps with good lighting you could examine this.
Another area that could be leaking is where the return hose connects to the right side of the top of the tank. This is a difficult area to access but warrants checking.

[Jim Gagliardi]

Re: 1972 Gas tank

Any reccomendations on where to buy a new tank?

Thanks, Jim

[Jim Gagliardi]

Re: 1972 Gas tank

Any reccomendations on where to buy a new tank?

Thanks, Jim

[Terry M.]

Re: 1972 Gas tank *TL*

Jim,

Try to find the point of the leak. On 1971 & 1972 (also 1970 with NA9 evap Emissions) there is a plastic fuel vapor separator on the left (driver's side) of the tank, high up. The plastic deteriorates and cracks. I am not aware of a source other than salvage yard for this item. Perhaps others can advise a source.
You have several other excellent suggestions posted by others. Try to find the source and repair it. Leaking gasoline is NOT a good thing.

Terry

[Terry M.]

Re: 1972 Gas tank *TL*

Jim,

Try to find the point of the leak. On 1971 & 1972 (also 1970 with NA9 evap Emissions) there is a plastic fuel vapor separator on the left (driver's side) of the tank, high up. The plastic deteriorates and cracks. I am not aware of a source other than salvage yard for this item. Perhaps others can advise a source.
You have several other excellent suggestions posted by others. Try to find the source and repair it. Leaking gasoline is NOT a good thing.

Terry

[Joe L.]

Re: 1972 Gas tank

Terry----

As far as I know, the plastic seperator, originally GM #7028035, is not available in reproduction or from any other replacement source, other than used as you point out.

This is going to create an interesting dilemma for 70 with EEC and 71-74 restorers, or even just owners, as time goes on. These pieces are plastic and subject to deterioration. They are also very necessary if the EEC system is to remain functional and safe. We'll have to see if someone "steps up to the plate" to reproduce and make available this piece. The problem is that since it's a fuel system component, product liability issues might stand in the way.

[Joe L.]

Re: 1972 Gas tank

Terry----

As far as I know, the plastic seperator, originally GM #7028035, is not available in reproduction or from any other replacement source, other than used as you point out.

This is going to create an interesting dilemma for 70 with EEC and 71-74 restorers, or even just owners, as time goes on. These pieces are plastic and subject to deterioration. They are also very necessary if the EEC system is to remain functional and safe. We'll have to see if someone "steps up to the plate" to reproduce and make available this piece. The problem is that since it's a fuel system component, product liability issues might stand in the way.