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1981 U1300L
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1,302 Posts
Discussion Starter #1
i geting ready to do something about the rust that has formed on the exterior of the tank where it contacts the support bracket. its not rusted thru or leaking yet. im sure ill findsome deep pitting when i get it off and clean it up. my question is....how to fill the pitting, and protect against further rust. weld? braze? jb weld? i know many of you have had exactly the same issue....what process works best?
 

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'88 U-1300L, '70 406, '78 406, '78 416 project, '82 406, '57 404, '65 404, '70 404, '68 Haflinger.
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1,849 Posts
B101UK's suggestion is ideal. If you don't want to work with solder/lead, POR 15 seals smaller perforations, and POR-15's putty will handle the larger holes. Sand blast first as he said and apply the POR-15 to the outside. A second coat while the first coat still has 'tack' will fill better.

I did this to a 404 gas tank in 1999 and it's still holding fine. That tank had some kind of corrosive splattered on it before I got it and had at least 50 small holes in the tank. I later bought a replacement but have not needed it!
 

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1984 406
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565 Posts
I did this to my 406 tank a while back. Check out this thread "406 FUEL TANK WANTED. " It shows my pictures and the advice from everyone when I started. Yes some of my solder could have been better but hey, it holds fuel and it usually is covered in mud.
MUD
 

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1984 406
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565 Posts
I power washed mine first with a really good degreaser a couple of times and then sand blasted it. I tried a small butane torch like you use to solder copper pluming lines together but the metal was too thin and melted through. I finally just sat down with a small soolder iron and a few beers and filled the holes. It took a few times of checking with water but I got it. Then I just followed the directions on the POR-15 can. I just used 60-40 solder also. Good luck!
MUD
 

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BenzWorld UNIMOG statesman
Unimog 404.1 Diesel (sold :( )1995 LMTV 1078
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5,856 Posts
if i drain the diesel and place a hose into the tank with argon or c02 will this make a safe job of brazing the tank?
I've heard diesel exhaust works well.

This is diesel though. Its less of an issue than a petrol fuel tank.
 

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1973 404.1
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16 Posts
I had a problem with the gas tank in a 75 911S. Bought a new one from Arizona so not to have rust. Not long after it also became a problem. Took Months, almost a year, to figure out that is was a crack rubber 90, part of the tanks breather, that routes through the wheel well. Damage snowballed and it became very expensive.

This time I sent the tank to Moyer Gas Tank Renu. Moyer Fuel Tank Renu - antique gas tank repair restoration, classic car gas tanks GASTANK
they sand blast inside and out, repair if needed, and coate it with some stuff inside and out which is baked on. Has a lifetime warranty, no more rust

It cost around $400. including shipping there and back, and that's because the Porsche tank is an odd shape, a depression for the spare tire to sit in, and has a long fill tube. A friend paid just under $200. for a 73 comet. A mog tank should be even easier for them to do.

If your tanks are rusting on the inside this is a good option or replace them with new. Moyer will cost more than new tanks but you might aviod a costly nightmare if you all are getting your machines wet often.

If I had it to do over I would buy the single tank or add another tube between the tanks at the bottom. The jerry can is your reserve tank.

When welding a gas tank replacing the oxygen with any gas thats not an oxidizer should work. A friend ran a hose from his exhaust pipe into the gas tank and ran the engine while he welded. I would think a full tank opposed to one empty, would be safer also. Personally I wouldn't do it. Spend some money and fix or replace.

One more option is the Redneck fixall. Duct Tape. There should be one that is fuel resistant.
 

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1981 U1300L
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1,302 Posts
Discussion Starter #11
well....i may have to puss out on the brazing idea...im still remembering a local welder sent to the hereafter while fuel tank welding not too long ago. im leaning towards sand blasting, followed with the entire line of por-15 products! if a sudden windfall comes my way id get one of those sweet aluminum tanks from england...thanks for all the input
 

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mogless, except for my friends MB4-94. And a bunch of other diesel junk.
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2,512 Posts
Kris, I just fixed a tank (non mog) a quick and easy way. The repair looks good, and I expect to get a few years out of it. Pressure washed the inside, what I could get at, with some detergent. Sandblasted the outside. Used sprayglue to adhere a layer of fiberglass cloth over the whole tank. Coated the cloth with THIS STUFF
and used the 205 fast hardener. No explosion, no shipping, probably good for a long time. I did my mog tank the same way with polyester resin, but that stuff has MEKP and is really nasty to work with. The epoxy is ok to work with. HTH,
 

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1962 404, (sold now, saving for the next)
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126 Posts
Just FYI - There is a product called Red-Kote that I've seen used on old bike tanks, it is some kind of polymer coating. You pour it in, slosh it around and pour excess out. It gets used when the original paint is valuable. It looked ok fresh but I can't vouch for its long term performance. Fuel Tank Sealer
Don't use a similar stuff called "Kreem", it tends to get gooey then come off and cause more problems than the rust.

As far as welding, I watched a guy seal up a large leak in my BMW's aluminum tank when I sprung a leak from internal corrosion in Utah. He just dumped the fuel out and ran a hose from his truck into the tank and welded it up. I stepped back really quickly but he said if the fuel system was working right there was little to no oxygen in the exhaust.
 
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