repairing dent in M gas tank

S2710

Well-known Member
I have a Farmall M with a dent in the top of the tank. The dent is about 8 inches long and about 2 inches wide and at the deepest part about 3/4 of a
inch. What is the best way to repair it? Can a person fill it with bondo or will you have to pull it out first? The biggest reason I would like to repair
it is the inside of the tank is perfect,just like when it came from the factory 70 years ago.

Bob
 
If the dent isn't too rigid you might pressurize the tank with compressed air and push most of it out. Putting bondo on it is asking for trouble as gas eats up bondo quick. You would be better off using an epoxy such as PC-7 epoxy however gas will get too if soaked long enough. Using a filler you would have better luck if you would strip the area to bare metal, use a epoxy primer and then the filler. Then when you have it level epoxy prime the area again. This will help seal in the repair away from the affects of the gas they make today.
 
Dunno, but the compressed air idea would make a bomb. That's what high explosives do, generate huge amounts of compressed violent air shock waves. Don't do that idea, at least. You might actually DETONATE THE GAS FUMES, IF ANY, BEFORE ANYTHING ELSE.
 

That is too deep to try to fill. What I would do would either buy one of those dent pullers like Eastwoods sells, that enables you to weld a post to the surface to have something to pull on, or just weld a few little cap screws head down to the dent and use my slide hammer to pull it out.
 
Motorcycle guys have been pushing out dents with compressed air for years . Braze a shrader valve to an extra tank cap . Apply heat as well if needed. { way too thick for bondo] . Your pressurizing it not exploding it.
 
I would shy away from the air pressure. Sounds more like a "crease" than a shallow dent. Air will NOT push out a crease and marginal on even a shallow dent. I use the elect stud welder like Eastwood sells. I bought one from auto store years ago..paid for itself first time use pulling a door crease out of a Camaro with the guard beam in behind outer panel. Weld on a row of studs and slide hammer them until dent is 95% out (leave it just a tad low so it will fill) then snip off the studs, grind and fill. I'm sure you don't have one and are probably not going to buy one for just this project. Take it to a good body shop and I'm sure they would use theirs to pull it for you and then it will take very little filler to smooth out. Make sure they hold an air blower nozzle blowing into the tank while doing this as the stud weld will "glow" when penetrated good. With air blown in it will never have a fuel / air ratio high enough to support combustion. If tank is a clean as you say, it probably wouldn't even be a problem anyway.
 
Randy thanks for the reply. Yes it is a crease. I am not going to buy a stud welder, so I have a dent puller the kind that you drill a hole and put a screw in and pull it out. Do you think I could do that and after I get it pulled out can I put screws in with a rubber washer and then use bondo to finish it.

Bob
 
nope, dont drill holes in the tank. the tank on an m is pretty sturdy. it also has a baffle in it. i have straightened them using the stud welder, and also used a pick rod thru the filler neck hole. you will need to get some heat on the dent to work it out. that means cleaning all the fumes out of the tank before working on it. if you dont have the equipment to straighten it, either take it to a body shop and let them pull the dents, or just bondo the dent as is. it is not the best, but, way better than drilling holes.
 
Next best if no stud welder would be to either braze or solder or mig weld washers on edge so you can hook a slide hammer or other suitable pull device in the hole in washer and pull out. Grind off washer weld as apposed to tearing it off as you will then end up with a hole to repair. If you drill holes to pull with then you have to weld them shut...if you have a welder to do that then use it to weld washers on instead.
 
Glen thanks for the advice, I think I will shine it up and fill some of the crease in with JB weld and bondo over the top if you think that will work.

Bob
 
nix the jb weld. you can use a fiberglass reinforced filler like kitty hair to fill the major portion, do your rough bodywork, then skim coat it with bondo. napa will have the kitty hair. tiger hair has a longer coarser strand fiberglass,which you wont need for your application.
 
Nobody said anything about putting 200 psi in the gas tank. It usually only takes 30-40 psi to push out a dent. That is completely silly to think compressed air could ignite gas vapors.
 
I wonder why so many are opposed to drilling holes and using a slide hammer. It is easy to solder the holes and if a hole is too big to solder easily just cut some round heads from galvanized roofing nails and solder them over the holes. I dad a nice Eagle gasoline can for my chainsaw and dropped a tree on it. I cut a hole about 2 inches in diameter in the bottom and pressed the dents out with a heavy bar then made a galvanized patch over the hole and soldered it in place. I am a retired sheetmetal worker and am competent at soldering. Did this at work after hours.
 
with the situation he has, i would rather he didnt drill holes. the tank is good, but has a dent. once you drill a hole, its there forever. it sounds like he is limited on the tools he has available, so its easy to end up in a worse situation than you start with. with a mig welder, he could use some tack and pull plates, weld flat washers to pull off of, or even use solder plates to pull the dent. i did an m tank a few years ago that was stuffed in good. chained the tank to the frame rack, mig'd some tack and pulls to the dents, then used heat and a long pick to work the dents out.
 
The way I repair dented gas tanks is to find a better one..
Theres lots of M Farmall tanks available..Earlier this year
I could have gotten one for $50 from a nice M that was parted out..
 
Carry the tank into a couple of auto body shops and ask for an estimate. They should be able to do a better job the first time and at a reasonable cost. Unless you plan to repaint the entire tractor, I would be tempted to either leave the dent or replace the tank.
 
For what it's worth, any time I see anyone using any kind of welder on a gas tank, I prefer to be about 100 yards away with my fingers in my ears.

I learned that the hard way when one blew up.
 
I have done the following on several gas tanks in the past.Hope I can explain it clearly. Leave the empty tank fastened to the tractor. Hook a 1 1/4 dia rod that has a 90 degree or more bend in it to the cherry picker. Put the other end of rod into the tank , get it rite under the dent or what ever. Carefully lift the rod with the " picker" . It mite take several tries , but it has always worked for me.
As a caution , I wrap a piece of rubber on the tank end of the rod , hopefully to elimate any sparks if the rod slips. If there are small dents left, they were filled with Bondo.
If needed, we have litely hammered on the tank just to" fine tune the dents.
 
Well for me, after all this, I have to know how this all worked out. You have to tell us, what did you finally do?
 
Thanks for all of the ideas fellas. I think I will try oleclint's idea and if that don't work I will use the kitty hair like Glennster said. I don't need to fill the tank full because the tractor only gets used for tractor rides, and light chores.

Bob
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top