Gas tank repair

[patrickg]

I have a VW beetle tank that has been struck by and rubbed by the steering damper on my Myers Manx style fiberglass dune buggy. It leaks profusely now and is out of service pending repairs. Otherwise the tank is in good shape, not rusty or anything so I don't want to install some junk yard replacement every year or two as I have to dissasemble the front of the car to get to it. I want to do a good job on this one. Being mildly afraid of welding on something full of gasoline fumes I thought I might tap the TBN brain trust.

I thought maybe a little water and dry ice might help. It would makek lots of CO2 which would dispell the air (O2) so I could weld with impunity. First I want to smack it a good lick with a large hammer to dent the area needing repair in out of the way so it will never contact the steering damper again. Then I suppose I should braze the area that is cracked open. I thought I might drill a hole through the tank at each end of the crack to relieve the stress prior to brazing but would like comments from the TBN braintrust before proceeding as I am only guessing. Oh, by the way, I have never brazed anything before but understand it is a lot like soldering. I even considered tinning the crack and surrounding area and filling it with solder but then thought HECK, I bought some brazing rod and flux and it is about time I tried to use the OTHER tip that came with my Oxy-Acetylene "cuting" rig.

I went to a motorcycle shop today and bought a kit of chemicals to clean out the tank, etch it, and then plastic coat the inside to guarantee it to be leak and rust free. Any suggestions on anything to do in advance to ensure a good job or lessons learned by using this coating method will be gratefully received.

And finally, is there any good protection methods for the outside of the tank. As I will be running through a lot of water, running river beds, I would like to supress rust on the outside as well. How about a good cleaning, spraypaint, and then a good coating of automotive undercoat (spraycans)? I'm open for suggestions as my previous dune buggy experience was in the desert and on the beach along deserts. Although you get salt water at the beach it dries real well in the desert and doesn't do much damage before you get the chance to rinse it off and then being in the desert it dries again real fast.

Patrick

 

[EdKing]

My local auto mechanic uses a product called JBWeld to fix gas tanks. It is some sort of epoxy, but claims to be strong as steel. He just cleans the area up real well and uses the JBWeld to fill the hole. As far as I know, he has never had one come back. Much safer than welding or brazing.

 

[Anonymous Poster]

Safety! Safety! Safety! The reason it is so dangerous to weld a gas tank is because the metal is porous and therefore you can never adequately clean it to the point where explosive fumes will not be released when the metal is heated by welding. Make darn sure that you know what you are doing here or you are going to get into big trouble. I would give a shop that specializes in gas tank repair a call and see what they have to say.

 

[patrickg]

Thanks a lot, ED you ole spoil sport. How am I ever going to learn to braze and make explosive situations safe enough without practice?

Yeah, I've used JB Weld before. lots of marine applications. Suggested it to the mech who pulled the tank. He said he recommended taking it to a radiator shop and having it cleaned like a radiator then brazing then plasticoating the inside. First he wanted to install a poly tank inside the vehicle up on the roll bar for gravit feed. I DON"T THINK SO. NOT THE WAY I DRIVE IT. I want it to run like a bomb not actually be a bomb.

Patrick

 

[patrickg]

Kubotadriver

I do appreciate what you are telling me. It is virtually impossible to get rid of all the gas fume capability by simple means. To get combustion or an explosion requires not only fuel (gas fumes) but oxygen in sufficient quantity to make a proper fuel air ratio. By flushing the tank with CO2 and working on it only while full of CO2 there is no explosive mixture. If I were going to arc weld it with my wire feed gun I would fill it all but a very small pocket at the weld site (tank shape supports this) and have at it. Unfortunately my skill level and past experience indicate that it is a real dumb thing to attempt as it will almost surely fail. As fast as I repair a hole I burn another, fix that but burn through another etc. Been there done that, hated it a lot.

While writing this another thought came to me. Fill the tank with dry sand. This will displace most of the air and remove the oxygen to a large degree. This will reduce the effective volume of the tank to reduce its explosive power. Next hook up a CO2 source (welding gas bottle) to the fuel line connection and flush out the air from in between the sand particles. As CO2 is way heavier than plain air or oxygen it will fill up the space between the sand grains like water would and displace the air/oxygen. Now heating the tank will not cause an explosion. Even a little sand in contact with the braze area (other side from where I put flux and brass) will not cause too much problem as sand is not a good conductor of heat.

Still think you should pass the hat, buy a life insurance policy on me, and make the stakek holders the beneficiaries?

More likey you will win the big lottery which is 17 times less likely than being killed by lightening.

Patrick

 

[cp1969]

In younger (and more foolish) days, I brazed a leaky Triumph motorcycle tank.

All I did was run a piece of flex tube from the tank inlet to a car's exhaust with the idea being that the car's exhaust was inert enough to prevent an explosion, which is apparently did. Nevermind the fact that working in that close proximity of CO was a health hazard in and of itself. I don't know where I got the idea to do it that way but I wouldn't do it again.

The next tank I repaired was one that had a flap cut in it to extract solidified fuel (looked like asphalt after a ten-year sit). I soldered it shut using an enormous iron. It didn't work very well, but don't remember it leaking before I sold the car.

Today, I would probably use body putty.

I was at a chemical plant when an accident occurred which killed three workers. They were taking down a 10,000 gallon tank which had held alcohol. They were trained workers and had taken every precaution but when one of them put a cutting torch to a catwalk (not even the tank itself), it blew.

 

[Von]

Patrick,I have done a bunch of tanks when I owned an auto restoration shop. If the tank is out flush it with water 3-4 times and than pass the torch over the fill tube and you will get a small pop as the last of the fumes burn off. Then solder it, as brazing is harder to do. If you have not done it before, you may do more damage to the tank. I have both mig welded and solder/brazed them and have never had one bo balistic on me. Have fun with it, sounds like a neat toy!

 

[tgello]

patrick, my grandfather was a welder for over 75 years and fixed thousands of tanks without ond blowing up. his recipe was to claen the spot with a wire wheel prefferably bronze to not cause excessive sparking. then he would cut a patch out of copper cutting the corners off on a angle. he would then clean the area with muriatic acid ,also the edge of the patch. then he would heat up a copper soldering iron in a propane heater like the blacksmith guys use. he would solder the patch using a solder on a roll with acompasition of 50/50 witch is 50%tin 50%lead.keeping the iron pressed on the edge and drawing along while feeding the solder. the key is to have a hot iron ,but not cherry red..he told me the copper was used because it would expand and contract with the tank when at different levels of fluid and outside temps...tgello

 

[patrickg]

cp1969 Dear cp, I know what you mean, I was once younger but I'm not sure I was more fooolish. There seems to be a body of believers in the inert qualities of automotive exhaust. My friend/neighbor that I gave my removed in-ground 10,000 gal diesel tank to, ran truck exhaust in to it for a long time and then shot it with his .243 (??????? I didn't ask) Apparently he thought if it was going to go bang it would do it when shot... He was suprised that he shot right through, in one side and out the other, he didn't think the .243 would do that, sure educated him.

It didn't explode when he shot it , so he attacked it with a cuting torch (still no explosion). That was diesel, gasoline might gave made for a different ending.

Body putty is essentially (we talkin' Bondo type here?) polyester resin with filler. GRP, FRP whatever you call the typical polyester saturated glass fiber that laymen call fiberglass is not gasoline tight. Liquid gas doesn't drain through it but it will pass gasoline molecules. Not fast enough to look like condensation on the outer surface but fast enough to put a heck of a lot of vapor in the air on the outside of a container. Can cause an explosive hazzard in an enclosed underventilated space like the typical garage.

Don't use polyester resin based products like bondo or fiberglass to contain gasoline. There are epoxies that will contain gasoline and can be substituted for polyester in making fiberglass gas tanks or repairs. I had to replace a zink coated steel fuel tank in an ocean going sailboat and luckily I had learned about the polyester and found a fiberglass shop also in the know to build me one with appropriate epoxy resins.

The JB Weld product is a good choice for "that kind of repair." It happens I'm sort of looking for an excuse to use that other torch tip that came with the cutting rig and the brass rod and flux I bought a couple years ago and havent used yet.

Patrick

 

[patrickg]

Von, thanks for ringing in. Nothing like hearing it from the guy who has been there, stayed a while, did it a bunch, and shares the knowledge. I gather there is no technical reason to NOT BRAZE rather than solder or JB Weld except skill required. OK, OK I'll practice a bit first like when I taught myself to stick weld and use the wire feed gun. Tried to use the wire feed gun on a fuel tank once. What a bad joke. I would have been fun to watch. Like a bear cub with boxing gloves on trying to get honey out of a hive by treating it like a punching bag. Every time I got close to "finishing" I'd burn a hole and start again. Same results trying to make an old rusted out VW rim hold air. It was a gonner, Ghandi and Mother Teresa working together couldn't have performed the required miracle.

I have watched closely as a friend (WW II Navy vet with decades of experience) has done various brazing jobs. He has several decades of experience as a refrigeration mechanic and assures me I can braze it.

What are the top 2-3 concerns with a beginner trying to braze? I have had extensive soldering experience in electronics with resin flux and in sheet metal with acid flux using various alloys of solder and some exotic fluxes for aluminum etc. Is there something to brazing that is a lot different?

Patrick