Gas Tank Repair - How to be safe?

[Whiplash]

Well I found out where the gas smell was coming from my 71. Since I had the rear end out of the car I pulled the tank. Wasn't any rust through or bad hose lines. It appears it was the gasket around the filler neck. I didn't find it until I tipped the tank over to drain the last half gallon out into a 5 gallon bucket. Low and behold instead of draining out of the giant hole for the filler neck it was draining from around the filler neck. This is what ruined my tank sticker and caused the bad gas smell only with a mostly full tank.

I have a few questions for you experts out there.

1) What's the best way to rinse/clean out the inside of the tank that won't damage the sending unit/guage but will remove the fumes?

2) Given your answer to option 1 above will the tank now be safe from any spark hazard? If I remove the bolts for the filler neck I want to be sure sparks won't be an issue.

3) Can you clean the inside of the tank with the sending unit still attached or does it have to be removed?

4) Can you remove the sending unit without a special tool?

5) There's a little bit of surface rust inside the tank probably due to the car sitting with only a half a tank for a long time. Seems to be just a ridge in one place. How can you remove this rust?

6) The outside surface of the tank has some surface rust. I could probably wire wheel this away or sandblast if that is better. What's the best way to remove this minor rust? Will the cleaning suggestion from 1) above make it safe?

7) Once cleaned should the tank be painted on the outside? Color? Brand of paint?

8) Should I just have someone else do this? I'm thinking radiator shop... Suggestions?

Sorry for the long list. I can fix the leaking gasket no problem but as long as I have the tank out I'd like to fix it for good.

Thanks for any responses.

Whiplash

 

[Ken]

I don't know squat about the C3 tanks, but I do know enough about gasoline vapors and explosibility limits, so be sure to purge the tank thoroughly before beginning any type of work that involves the possibilty of sparking.

Water will usually do the trick if enough is used, but something in an inert gas, like nitrogen, is best.

I imagine the sending unit is easily removed, and you should not have to worry about sparks emanating from those bolts; they're designed not to cause spark, plus there's enough sealant around that area that a spark is probably very difficult to create.

 

[wishuwerehere82]

If the sending unit is like other GM vehicles of that era. the unit is held in place with a Circular retaining ring that can be removed by prying up the locking tabs and rotating the ring to unlock it. it may need a little tapping with a chisel to loosen it, so make sure the tank is fully purged. CO2 from a beer tap will displace the air in the tank as it is heavier than air, also will prevent ignition.

 

[paintdaddy]

Save your self some time and aggrivation,buy a new tank,and sending unit.The last I checked on one They are on ebay for about 150 and 50 for the sending unit.Its safer and full proof.

 

[bradfordsvettes]

As far as i know the gasket is servicable i believe it is just a cork gasket . unless i am thinking if a newer model . If i remember right the seal was leaking on my 69 and made a gasket from a sheet of cork. hope this is not a bum steer but it should be obvious with the tank out Steve

 

[74bigblock]

It's not worth the hassle to repair the interior of the tank. It would require special sealants etc. Just get a new tank. If there is nothing wrong with your sending unit, then just reuse it. The tank will come with a new cork gasket for the filler neck. You should also save the gas tank straps and pads, and reuse those if they are in decent condition. It makes it a lot easier to get the replacement tank in place and bolted up... as the straps are a PITA to work with if not pre-shaped to the tank.

-Dave

 

[Red69]

I agree with other comments, if your tank is near failure, don't waste time and money trying to save it. Replace it, been there-done that! Repro gas tanks are now only $200, I paid $300 for a NOS tank 20 months ago and just before repros were available. Trying to save the old one cost half that if my time is worth anything and eventually failed anyway. If your sending unit is working now no reason to replace it. It is removable simply by unscrewing the lock-ring by tapping a bottom blade with a flat object and hammer. A rubber o-ring is sandwiched between the sending unit bottom and tank forming a seal. Buy the correct o-ring and seal it the way GM intended. If it doesn't work after replacing it, you may need to ground it first to get it going again. After having gone down that road, that is what I did.

 

[Whiplash]

I agree with other comments, if your tank is near failure, don't waste time and money trying to save it. Replace it, been there-done that! Repro gas tanks are now only $200, I paid $300 for a NOS tank 20 months ago and just before repros were available. Trying to save the old one cost half that if my time is worth anything and eventually failed anyway. If your sending unit is working now no reason to replace it. It is removable simply by unscrewing the lock-ring by tapping a bottom blade with a flat object and hammer. A rubber o-ring is sandwiched between the sending unit bottom and tank forming a seal. Buy the correct o-ring and seal it the way GM intended. If it doesn't work after replacing it, you may need to ground it first to get it going again. After having gone down that road, that is what I did.

Thanks everyone. The tank is no where near failure. Buying a new one is kind of a waste. It just has some surface rust on the outside and a small amount of surface rust on the inside. (By small amount I mean you can just see a very thin line of discoloration/rust where the tank was left half full for a while. By surface rust I mean surface, a few passes with a wire wheel or sandpaper and it would be gone. Very little elbow grease required) I just want to clean it up so it doesn't fail. The gasket on the filler neck is definitely cork and I know where to order it. My concern is how to evacuate the tank completely so I can wire wheel the outside. I also want to pull the sending unit so I can replace the sock while it's easy to get to. Finally, I'd like to spray it to keep it from rusting in the future. I will need new pads but the straps are in great shape.

Also on another note. I've been thinking about putting in fuel injection when I replace the motor. Is there any reason I cannot just use the return line that's already on the car and connection point already on the tank for the FI return line?

Thanks

Whiplash

 

[Ol Blue]

whiplash

You might consider spraying Oxysolv to remove the rust instead of a wire wheel. I've had good luck using that to remove light rust on other things.
Ol Blue

 

[GTR1999]

Whiplash,
You can certainly save it as long as the internal rust is only surface rust. I have done this. You have the tank out, call Quanta in MD and get the tank kit. It will have new screws,o rings, gasket, sender O ring and maybe a new lock ring. Buy the lock ring if it doesn't come with it. You could buy the strap cushions but they are roofing tar paper you can buy at home depot. Call Eastwoods and get the gas tank/sealing kit. It takes some time but it works. Spray the outside with cold galvanize from Home Depot or the tank paint from Eastwoods. Remove the sender, it's not hard, just be careful with it and buy a new sock for it.Total cost should be under $100, or you could just buy a new one for $200. The vendor do need your money
Good luck

 

[Bob Chadwick]

Be careful with that empty tank. The fumes in it literally make it into a bomb. It is more dangerous empty than when full.

When CHP did their article on removing the fuel tank they recommended filling it with water and then draining it.

 

[Whiplash]

Be careful with that empty tank. The fumes in it literally make it into a bomb. It is more dangerous empty than when full.

When CHP did their article on removing the fuel tank they recommended filling it with water and then draining it.

Bob,

Thanks. I completely understand the "bomb" statement. In fact that's what prompted me to start this thread. My current thoughts are to fill the tank with soapy water and work on it while it's full of water. What I was hoping for was a solution that would allow me to rinse the tank without having to worry about fumes at all. My concern with rinsing with water is whether that would actually get all the gas residue out. If it doesn't all I've done is fool myself into thinking it's safe. It doesn't take much fuel vapor to make the tank as dangerous as a grenade.

Will rinsing with soapy water remove all the gas and resulting fumes?

I'm also thinking about brining it to a radiator shop and having it boiled. If they would even take the tank at all.

I just want it safe to work on. The repairs themselves are a no brainer.

Keep the thoughts coming.

Whiplash

 

[Chuck-75]

One of my CoWorkers took his pantera tank to the Radiator shop and they boiled it and also resealed the inside. call around town and see what the Radiator shops charge?. here, it was about $200.00, same for a new repo. vette tank. Im about to remove my tank and its a lot easier to remove when empty . Im gona put carpet down under the car (just to avoid possible sparks), Ive removed gas tanks before, yr not disarming a landmine, but be VERY-Very careful, go slow. and take yr time, if yr doing any hammering? use soft metals that wont spark. (I think Brass,is one) in case you have to use a chisel. like to remove the ring retainer, and rubber mallets are great .my 94 chevy truck uses a rubber ring seal, and then has the black caulking to give more sealing around the ring.(on the outside ).hope this helps.
save the wave,

 

[Bob Chadwick]

Whiplash,

The article I read was about a year ago. I don't even think they suggested leaving water in it. My recollection is that they said to fill it and drain it.

Bob

 

[norvalwilhelm]

Any gas tank can be quick made safe for welding in about 5 minutes. My son repairs tanks and taught me how.
I remove any covers that I can then take the shop vac on blow, not suck and stick the hose in the tank. In as little as 5 minutes the tank is safe to use a flame on it but I prefer to let it sit for 30 minutes with the air blowing through the tank.
I have done numerous tanks, welding dual outlets for racing withou a problem.
In a shop time is money so they allow 5 minutes and have no problems.
It is scary the first time but I haven't had a problem introducing a welding flame into the tank after 30 minutes.

 

[Whiplash]

Any gas tank can be quick made safe for welding in about 5 minutes. My son repairs tanks and taught me how.
I remove any covers that I can then take the shop vac on blow, not suck and stick the hose in the tank. In as little as 5 minutes the tank is safe to use a flame on it but I prefer to let it sit for 30 minutes with the air blowing through the tank.
I have done numerous tanks, welding dual outlets for racing withou a problem.
In a shop time is money so they allow 5 minutes and have no problems.
It is scary the first time but I haven't had a problem introducing a welding flame into the tank after 30 minutes.

Thanks. I combined a number of suggestions to get going on the tank. I flushed it with soapy water and let the water run in the tank while I removed the bolts around the filler neck to remove. I then knocked the sending unit out and drained the tank. Once drained I used my shop vac to suck both the air and left over water out of the tank. (My shop vac doesn't have a hose connection for the reverse/blow function). I let the vac run for 30 minutes just to be safe.

Alas ad now that I have it all safe to work on I found a very small pin hole in the bottom of the tank:cry . It's nowhere near any rust so I'm thinking it's a function of friction on the frame. I was so mad I gave up on cleaning the outside of the tank for the afternoon. I'm now researching my options.

Please send comments anyone on the following:

1) Is it even worth having one small pin hole welded? My fear is if there's one there's more coming.

2) What would you expect to pay for the repair?

3) Options on replacement tank? Best vendors? Is there a larger tank? Is there a tank that would lend itself to a potential fuel injection modification?

Thanks. I'm hoping this thread isn't getting too long/old to get more feedback.

I appreciate all the previous suggestions for saftey. Thanks everyone for that feedback.

 

[paintdaddy]

I hate to be the one that says "I told ya so"but like I said,its not worth the work,they sell on ebay for 150 .At worst they are everywhere for 199.Even if you save the tank by fixing the one hole there may be places where the metal is thin and on the verge of producing another,just spend the money and have confidence that you wont have anymore problems. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=4529456445&category=10076
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=4531140616&category=34198

 

[Whiplash]

I hate to be the one that says "I told ya so"but like I said,its not worth the work,they sell on ebay for 150 .At worst they are everywhere for 199.Even if you save the tank by fixing the one hole there may be places where the metal is thin and on the verge of producing another,just spend the money and have confidence that you wont have anymore problems. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=4529456445&category=10076
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=4531140616&category=34198

I know, I know, you said it first and I agree. I just wanted to give you a chance to say I told you so and give me a chance to look at your Avatar again. Besides, now not only do I have your word for it I've also seen it for my own two eyes. I should move to Missouri, you always have to show me .

Are you familiar with either of these two sellers? Since you mentioned these tanks usually sell for $150 on eBay I'm assuming you've watched them sell before. I'm surprised they sell for less than the catalogue companies as even Quanta sells for slightly more than the catalogue companies and they seem to be the OEM.

 

[paintdaddy]

Ive bought many of them,some for myself and others for customers.Im not sure but there only a few manufacturers of gas tanks .From what I gather there are some that have oem markings for a correct look and others dont .They all fit the same .Either way as I said befor use you original straps.They are like a road map,once there off they are a little hard to get back on but almost impossible to get new ones on.I was shocked to see the prices on these tanks are even coming down.Kepp us updated.