1987pachanga22

I have recently pulled my aluminum 96 gal tank out of my 217 Mirage intruder so that I can repair and replace some rotted wood. Now that I have all of the wood replaced I was about to reposition the tank back into its location when I noticed a small wet spot below the tank and what I found is that there is a very small crack right where there is a welded bulkhead inside of the tank.

So my question is how do I prepare the tank to be welded and or sealed in this area?

One last detail about the location is that it is a very rough looking weld that sticks out about 1/6” so it is not an easily patched smooth area.

f_inscreenname

If we are talking about your 1987 Pachanga 22 in your sig? You may want to consider a new tank. You are talking about a 25 year old tank. If you are going to fix it take it to someone who fixes gas tanks. They are a bit different then the average weld.

1987pachanga22

It is not out of the Pachanga but it is of the same vintage.

What is the difference between an average weld and a gas tank weld?

The tank is not corroded at all or in need of actual replacement because the aluminum materials are in great shape inside and out. This small crack is due to that fact that I flexed the tank through an already welded seam too much while moving it around for other repairs. I am not worried about the structural ability of this aluminum weld but I am worried about preparing the tank for welding without danger. I would gladly take it to someone that does tanks but I am unaware of anyone within a 4 hour drive that does this work.

mr3dman

you have to fill the tank with an inert gas like nitrogen/co2/ helium etc that wont allow combustion of the gas fumes. Keep the flow on while welding. also, better to use a heavier than air gas like co2 and tilt the tank so the weld is below the fill so the co2 etc..gas stays in the low area you are welding. Helium you have to tilt up. Ventalation or self contained air for yourself goes without saying I hope.

1987pachanga22

Thank you! That is the information that I was looking for.

I am still open to any other suggestions about other alternative methods of sealing or closing the crack.

Perlmudder

Probably not the best choice but what about the sealing stuff they sell at truck stops. I don't remember what it is called but you work the putty in your hands then cover the crack and it hardens?

dereknkathy

i brazed a hole in a motorcycle gas tank, heck 25 years ago. filled it with water. 5 times. held torch over filler hole. blew a flame 4 feet in the air. this from the residual gas soaked into a 4 gallon steel tank. a 100 gallon alum tank will put you in orbit. i don't think anybody who makes gas tanks will touch it. replace the tank. any glue-type patch on outside will leak, sooner rather than later. replace the tank. the moeller polyethelyne tanks are quite good, last forever, very tough, and half the price of welded aluminum. no baffles though. their one downside.

Hydrant

I've seen guy's get a bunch of dry ice pellets and drop in the tank. The CO2 will displace the gas vapors.

Using any inert gas that is under constant flow inside the tank will rid the fumes, but like the previous poster stated you have to tilt the tank to whichever gas you use.

Just found this one.

How to Weld or Repair a Motorcycle Gas Tank Safely

In order to weld a gasoline fuel tank safely, first remove all traces of fuel. Before welding, wash out your fuel tank with warm soapy water, then rinse with clear water. This should remove fuel residue.

Next, you'll need to remove all traces of flammable gasoline fumes. To remove the fumes from the gas tank, insert small pieces or pellets of dry ice into the filler neck of the tank. As the dry ice comes in contact with air, it will sublimate directly into carbon dioxide gas, which is the fog effect dry ice is known to produce.

Dry ice produces no liquid but rather sublimates from solid to gas. Because CO2 gas is heavier than oxygen, it displaces, or pushes out oxygen from the fuel tank. The fumes will be pushed out of the tank and without oxygen present, the risk for fire or explosion when welding can be eliminated if done properly using this dry ice technique.

Please use caution when handling both dry ice and flammable liquids. If you attempt your own repair, understand your limits and do not attempt a repair beyond your scope of understanding. Consult a professional if you are unsure about any of the advice presented in this article.


http://www.continentalcarbonic.com/d...th-dry-ice.php

jason y

on motorcycle tanks all we have ever done is wash them out with soapy water a bunch of times and let air out over night then went to town rewelded in some new fuel petcocks on one. with a tig . on the drag car i welded in a sump with a mig..old man showed me this we took the tank found a car with a hot exhuast/one with a catalytic converter usually,
put a hose from tail pipe to the tank and let the tank vent let the van run for about 20 -30 minutes then went to town.. find some one with a mig that knows how to use it they can fix that no sweat..
my guy that done the bike tank i didnt even leak check it i asked him what he thought he said what would be the fun in that .. put gas right in it no leaks.. he welds race car torque converters up on a daily basis

1987pachanga22

I have just talked to one of the local radiator shops in town who said NO PROBLEM! I guess they have a sure fire way to clean it out and at $125 there is no reason for me to worry anymore. Thank you guys for your helpful ideas and mr3dman for the actual information but I think I am going to let the professionals take care of this one.