MTFCA Forum

My '14 T has a very minor fuel tank leak in the area where the sediment bowl screws in and I'm going to attempt a soldering repair. I have a large electric soldering iron, and the tank is not rusty inside or out, so should I be concerned about a big bang ??? Not going anywhere near it with an open flame, just the soldering iron, solder and flux (tank is removed). The threaded receptical soldered to the tank, and the brass sediment bowl both have perfect threads but there is a minor leak in the soldered section within an inch of the threads . Comments.....

If it is an electric iron, or one heated on a fire which is away from the tank, you should be OK, but a torch or arc welder, is a no no.
Norm

We use a flame to weld on gas tanks all the time when making repairs. While I am not implying this based on above comments, I have found in listening to folks' concerns, it is that generally people who give advice about not welding on fuel tanks have never done it themselves and typically are working off of hearsay. They have read about it on social media site, or saw a picture somewhere depicting a gas tank was welded on and blew-up the whole building. The percentage of gas tank that "blow-up" compared to ones that are successfully welded on is very, very low. So below is how we successfully do it.

To begin with, drain the tank of all fuel. Next, thoroughly wash the interior and exterior of the tank using water and Dawn dish soap. On areas you cannot reach with a brush, fill the tank with soap & water, then use compressed air on a piece of brake line tubing to agitate the soapy water. Repeat this process until you can flush and only clean water exits. Remember, it is the fumes that ignite. The water has flushed away 95% of any residual fuel that can make fumes. The water has also banqueted what remaining fumes might be lingering. Place the compressed air back inside the tank thru the outlet port and have the fill-port open for the air to escape. Use a soft torch flame on the outside of the tank and move rapidly starting near the outlet port and moving over the entire exterior. This flame will warm the tank enough that the water will begin to evaporate and any remaining fumes are evaporated and displaced in the compressed air. Once the interior of the tank has been purged of the water, the gas fumes are gone too. This entire process from beginning to end will take about 15-20 minutes. The reason for needing the tank to be totally clean and purged of moisture is so the flux will not be diluted as you are prepping for the solder. You cannot 'over-flux' in this since this is the key to having a successful repair.

And, ...I know some are going to say that I am hiding behind a computer screen making up advice. Below are a few pix of tanks we have done in my shop. We are the largest restorer of Model-A gas tanks, and as of a couple of years ago we surpassed the 300 count of restored tanks. This number does not include the stray off-brand auto and tractor tanks we have done. So using an open flame from my experience is the prefered and much superior method to make repairs on a tank.

When I did the one on our 21 I just made sure to blow it out with an air compressor after letting it air out for a while and then soldered it with a torch. With an electric iron, I would still do these steps but I would most certainly be less worried. Most definitely better to spend a bit of extra time and play it safe.

A former student in the school where I taught was killed when the gas tank that he was soldering with an open flame exploded. Use an electric or gas-heated soldering iron. Thoroughly clean the tank as has been described in this thread, then if possible leave the tank out in the sun for a couple of days (obviously) with the gas cap off and the valve and strainer removed.

I have soldered a number of gas tanks.
Here is a bit of science; to have combustion you need an air to fuel ratio of no richer than 10-1 and no leaner than 14-1.
Hollywood does us no favors when it shows someone flipping a cigarette at a open gas tank and the car explodes!

When your tank is too far gone. T tanks are available but what about
others I had a 24 Franklin which also had the gauge in the top of the tank.
Yeah ,you had to get out and go around to the back to see how much gas you had ! I went to a company that made boat gas tanks. They made up an exact duplicate and put the gauge in too. So for those that have something other than a T you might try it.

So to summarize?

DON'T use a flame UNLESS you have purged and cleaned the tank thoroughly.

DON'T use a flame if you are not really sure what you are doing.


(And yes, exploding tanks are not just things in social media but they really really do happen to people we know. Probably because they did not follow the flush thoroughly rule. To get a combustion ratio you only need a tiny amount of fuel vapour. )

Bruce, I just did the same repair you are considering. I don't know yet if I was successful but the solder joint looks good. One issue you might have is getting the joint clean. My seeping was at the flange where the pipe comes out and as I heated the joint I could see a slight crack with some oily residue which I quickly hit with a bit of acid flux. The key to good solder joints is the acid flux and a clean surface and not over heating the joint I was told by an old timer radiator guy. He gave me a few sticks of solder and a jar of the acid which worked great.

Another option that some have used with success is coating the inside of the tank with a product like POR 15 gas tank sealer. It has good results but requires a lot of time and work and you must follow the instructions perfectly. Good Luck

The tank on my '10 leaked around the outlet. On the advice of a friend I drained the tank, let it air out and then hooked it up to the exhaust pipe of my modern car and filled it with the fumes for about 15 minutes. I was then able to solder it with my torch without issue. Don't know if I was just lucky or that method is safe. Unfortunately it started leaking again after about a month and my second attempt was equally short lived. I finally gave up and bought a new tank as they were still available at the time from the vendors.

The details by Brent are very good.
I did once alter a Chevrolet tank to fit in the trunk of a 22 Dodge Roadster body which I installed on a Model A frame. The A chassis came from a neighbor who removed the Roadster body to put it on a V8 frame.Since the A has a cowl tank, I put the tank in back and used an electric fuel pump. I still used the A engine. I wanted to move the filler neck from the side to the top. So I attached a plate to the opening in the side and cut a hole in top for the filler. I used an aceteline torch to heat things up. I knew the tank could explode, so I filled it with water. I couldn't get it hot enough to melt solder so I poured out the water. I don't know how long the tank had been empty because I got it in a wrecking yard. When I applied the heat, the tank jumped off the ground but did not explode in my face. After that I was successful doing the work. That was around 1954 when I did that. Someone whose house had burnt down had two cars setting in the yard which were free to anyone who would haul them away. The other car was a 24 Star sedan. My friend took the Star and I took the Dodge. I wanted to make a "Hot Rod" Everything went OK and I was already driving it around. But there were no top support rods for the radiator because the Dodge body didn't have a place to mount them. Only the hoses held the radiator on. Well! It ran until one day the radiator moved back into the fan and ruined the radiator. Anyway I think I got about 9 dollars for everything when I sold it. The friend got 75 dollars for the Star.
Norm

I have the same issue, leaky solder around the flange. I’ll clean it first, but don’t have any compressed air on hand. What I’d like to know is whether there is a way to do this safely without air - or an exhaust pipe.

So far, this is the plan:
Clean exterior with acetone, wash afterwards with simple green
Clean interior with water and simple green ( or Dawn dish soap ) repeat as necessary.
Let dry in sun for several days.

Does this sound reasonable, or is it an invitation for interior rust?

This 26 tank had been in a barn loft for no telling how long. I soaked it in a electrolysis tank for 2 weeks. I had no issues using a propane torch to solder this copper repair patch to it.

Stan
The air in a tank sitting in the sun will pretty much just warm up. After following Brent's great instructions, hook up a vacuum cleaner backwards to blow air through the tank. Works just like compressed air.

Save yourself a lot of anxiety and effort. Clean the area thoroughly, as f you were going to paint it, then use J-B weld or some there epoxy. Fiberglass resin will not work, must be epoxy, not polyester resin. No worries, little fuss, and if it fails you just grind off the epoxy and try again.

Loftfield wrote: ↑

Tue Mar 26, 2024 8:18 am

Save yourself a lot of anxiety and effort. Clean the area thoroughly, as f you were going to paint it, then use J-B weld or some there epoxy. Fiberglass resin will not work, must be epoxy, not polyester resin. No worries, little fuss, and if it fails you just grind off the epoxy and try again.

Agree. Had a seep on an under seat gas tank due to minor pin hole near the strap. Used this epoxy after sanding and cleaning the area. Slathered on and when dry no seeping again, lasted for years.

I'm not trying it. Not after I saw a motorcycle fuel tank launch 100 feet into the air while a friend tried to braze a hole. Repeatedly washed out also. I told him don't do it but he blew me off. As soon as the flame got near the tank it shot straight up into the air. Blew open like a clam shell and landed almost in the exact spot it took off from. To this day I don't think he realized it was gone until it came back. JB Weld is what I'd use. Or take it to a professional.

I’ve done both procedures to gas tanks in the last few years. Brent has outlined a perfectly safe procedure, but using the epoxy was sure easy. I stopped gas weeping from pinholes in my round tank with a light smear of J.B. Weld and a little sanding. Is it advertised as gas proof, can be painted and the one time repair has been working for nearly four years now.
Solder repairs to a cowl tank outlet were difficult to get clean enough since the crack was from the inside out through a thick section of the old solder. Varnish kept oozing from the crack and flooding the area with liquid flux kept cooling it off. I also felt like the tank needed to air out for a week after repeated washing and ran an air line while soldering with the torch. So after a week and a whole day that repair re-opened during assembly and had to be redone, where the epoxy just had to dry overnight after a good scrub and drying with compressed air.
I don’t mind doing things the long way and If I had two tanks and extra time I’d go for the torch repair, but if I was trying to drive the car sooner than later I’d at least try the epoxy fix as it is easy to remove if it doesn’t work. -Chris, in Boulder

I could not possibly disagree with Brent more strongly. I was a public school teacher, and one of my students was killed when repairing a gas tank with an open flame. He had done all of the things that have been mentioned to insure that there were no gasoline vapors in the tank. I would strongly recommend that an open flame not be used for the repair. I will agree that there's a good chance that you will get away with an open-flame repair, but if you are one of the unlucky ones, the consequences could be dire.

Think we need to put the arguments on repairing a gas tank in the proper perspective.
As stated, several times, the danger of an explosion is the presence of fumes in the tank not in the method of repair.
So the amount of heat applied better not be equal to the flashpoint of the vapor present.
--
From https://hypertextbook.com/facts/2003/Sh ... pher.shtml
"Gasoline has a flash point of about −45 °C. The flammable range of a liquid is the ratio of the flammable liquid to air that would create a volatile mixture. The flammability range of gasoline is between 1.4 and 7.6%. If the ratio of gasoline to air is less than 1.4%, then the mixture is to thin to burn. The mixture cannot burn when it contains more than 7.6% gasoline because it is too rich to burn.The vapor density is the weight of a vapor relative to the weight of air. The vapor density of gasoline is heavier than air and therefore will sink when in air."
--
And you know about a rich fuel mixture in a running engine
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YES that's a minus sign −43 °C = -45 °F --
--
The tank that was stored in the barn for years was without fumes. Cleaning the tank with a volatile fluid may add another combustible vapor. Putting the tank in the sun for a few days, with the filler cap opening towards the ground for the fumes to escape (potato removed too) may be the best way for fumes to escape.
--
Not sure what ratio solder is being used but likely Ford used 50/50
--
Bottom line no fumes - no problem. Case where there was an explosion - underestimated fumes
--

With the current tort laws I'm not recommending anything. We have buried a friend that had welded gas & diesel tanks for 40 years. I've seen
them blow up using the exhaust method ( engine to rich & hole in muffler ) I have seen a tank blow while it was being made (that had never had
gas in it yet) Torch was set with a carbonizing flame that may have left to much acetylene to linger in the tank. This can also happen when
brazing with a soft flame. If there is no oxygen there can be no combustion? I would assume that keeping oxygen out would be a lot like
welding stainless steel tubing to prevent oxidation of the weld inside the tubing it is filled with inert gas such as CO2 or argon with a constant
flow in & out so no oxygen can find it's way inside. The inlet needs to be sealed for the air so none is brought in with the inert gas.
The cost of having a professional do the job should be less than the ER deductible if just one detail is missed.
Craig.

DHort wrote: ↑

Tue Mar 26, 2024 3:04 am

Stan
The air in a tank sitting in the sun will pretty much just warm up. After following Brent's great instructions, hook up a vacuum cleaner backwards to blow air through the tank. Works just like compressed air.

DAVE, Or sneak you 'lady's' electric hair dryer out of the house and into the garage; put it on the hottest setting, and dry the tank thoroughly. Then replace it back before she notices it is gone.

ModelTWoods wrote: ↑

Tue Mar 26, 2024 12:21 pm

DHort wrote: ↑

Tue Mar 26, 2024 3:04 am

Stan
The air in a tank sitting in the sun will pretty much just warm up. After following Brent's great instructions, hook up a vacuum cleaner backwards to blow air through the tank. Works just like compressed air.

DAVE, Or sneak you 'lady's' electric hair dryer out of the house and into the garage; put it on the hottest setting, and dry the tank thoroughly. Then replace it back before she notices it is gone.

I guess you missed the point of the flash point being minus 45°F. Using the hair dryer on the hottest setting may be a bit premature.
Sucking fumes into a shop vac's through its electric motor with brushes isn't a good idea either.

John Codman wrote: ↑

Tue Mar 26, 2024 10:35 am

I could not possibly disagree with Brent more strongly. I was a public school teacher, and one of my students was killed when repairing a gas tank with an open flame. He had done ALL of the things that have been mentioned to insure that there were no gasoline vapors in the tank. I would strongly recommend that an open flame not be used for the repair. I will agree that there's a good chance that you will get away with an open-flame repair, but if you are one of the unlucky ones, the consequences could be dire.

Hi John, ...you are definitely welcome to disagree with me however I think I could make a very compelling argument that your student did NOT do ALL of the things as I instructed in my post above. For there to have been enough residual vapors to cause an explosion, then most true experts will testify that your student likely did not purge the tank as I instructed to do above.

As far as proving/disproving this myth about tanks blowing up, several years ago I took the liberty to drain both Model-T and a Model-A gas tank however I intentionally did not flush them. I only allowed the remaining fuel residue to dry. Suited in my babbitt-pouring attire (face shield, apron, gloves, etc.), on separate occasions I intentionally stuck a candle lighter into both of the tank and pulled the trigger to know firsthand what to expect if one of my employees were to do something incorrectly. Both tanks did have the fuel vapors ignite with a scary 'wooff' however neither tank deformed nor did either tank even jump off of the floor. Because of what I experienced both in these two tanks, -and what we have learned restoring quite a few other tanks, I feel fairly certain in making a public statement that your student either was not instructed on the proper protocol, -OR more likely that (s)he failed to follow their instructor's directions in 100% entirety. No one is discounting that an explosion can happen however someone must be educated on the proper and safe methods.

Secondly, this open flame advice is not correct either. Not all gas tanks can be repaired without using some sort of an open flame, -whether that open flame is generated from a torch or from an electric welder. Look closely in the pictures I showed above and you will see those tanks were cut open. This is a prerequisite on many tanks that need to be media-blasted and cleaned on the inside. Therefore, Soldering with an electric iron is definitely not going to work in this application, ...and being brutally honest here, an improper executed solder job (i.e.: too cold of a joint to have proper bonding and flow) on a Model-T tank has the possibility of allowing an end or seam of the tank to rupture and then potentially spill fuel onto a hot exhaust pipe.

Having been around fuel tanks for the majority of my life, I will relate the ways I have seen tanks that are filled with combustibles and/or HAD combustibles in them at some time in the past, be repaired.

The safest way to repair an empty combustible tank it to fill it with inert gas. Purge the tank with Argon or CO2. CO2 is the easiest to obtain. Find a dry ice seller. Purchase some dry ice (in small pieces if possible), get the dry ice into the tank and roll the area to be repaired as low as possible. CO2 is HEAVIER than air and will displace air and fumes up and out of the tank. Wait a few minutes to ensure the vapors have been displaced (I recommend putting a hose over the filler and directing it to a safe distance) and complete your repair. No oxygen and/or fuel vapors means you will be safe using an open flame.

The next safest is using the exhaust method as mentioned above. I recommend using diesel exhaust if possible.

A simpler CO2 method is to buy seltzer water or any carbonated drink WITHOUT SUGAR in it. Pour a few bottles into the tank and wait for the vapors to dissipate. Repair the problem, drain the fluid and dry out the tank.

A controversial method used by welders is to perform the repair on a FULL TANK. I have witnessed this method several times on a hydraulic thank. A welder, welded a crack in the side without anything more than ensuring the oil level was ABOVE the repair point. No oxygen = no flame or explosion hazard. This welder told of times he did the same on leaking fuel tanks though he did not address the fuel that had/was leaking during the repair.

Finally, if these methods are beyond your comfort zone: Take it to a professional!

When I was getting fire fighting training in the Navy, they had 5 gallon Jerry cans lined up along the fence, all with out lids. The instructor stated the cans had all been there for at least 6 months, open to the air and weather. He chose a man, sent him to pick out any can, and make sure to dump out any accumulated water that might be in the can. The man chose one, dumped out the accumulated rain/snow melt water and gave it to the instructor. The can was placed in a "blast cage" and a fuse was laid then lit. When the fuse burned down to the can, the can blew up. Thus, indicating, fuel vapors can exist for much longer than you think they can.

The KEY to safe repairs is to ensure the fuel to air ratio is BELOW the combustible limit.

Good Luck

We could discuss this until the cows came home.
The safest thing to do is never get out of bed! Anything else you do might risk injury.

So to summarize,

It can be done, but according to experienced perspectives, results can vary from safe to fatal. Fuel to air must be below the combustable limit - the best means of displacing fumes is mechanical, either by air, exhaust or CO2.

Extended soaking in an electrolysis tank is one approach, boiling it out is another, provided a capable radiator repair shop is nearby and isn't scared of anything that isn't plastic. Fumes can last a long time according to the jerry can demonstration, don't be fooled into assuming safety.

Alternately, JB tank weld can be used, with experiences generally favorable. Clean, sand, clean and prep again before applying.

Here's what I did:

I first rinsed the tank out with water, letting it dry in the sun for several days. I then filled it with water and about 1 1/2 liters of Simple Green before rolling the round tank back and forth along a wooden deck for a couple times, turning it into a washing machine. It was then rinsed with water until it ran clear, letting it dry in the sun for several more days. All the vapors are gone, and a match test (tied to the end of a long pole) showed no response.

At the Railcar shop, whenever we had to weld on a fuel tank, we pumped it full of nitrogen. Jim Patrick

I had the same issue with my T tank. Leaking where the sediment bowl screwed in. I took it to a radiator shop and they fixed it no problem. They steamed it first to remove any combustible gasoline.

when you are at an antique shop or a swap meet, keep an eye out for one of these copper soldering irons.
I use the oxygen acetylene torch to warm the copper head up to a dull red. They will hold the heat for a fair amount of time, and are totally safe to use, since there is NO open flame.
And, they are just the ticket for repairing radiators also. A torch is too hot and will carbon up the brass, and is not near as controllable as an old time copper soldering iron. The old iron puts the heat exactly where you need it, and nowhere else.