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Soldering a fuel tank


Paul Coleman

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There's probably a very good reason why I shouldn't do this and I think I know what the answer is but I'll ask it anyway... If I cut the bottom off my rusty fuel tank and just leave a 0.5" flange all the way around and then cut a piece of sheet steel to fit the bottom of the tank which butts up against the flange what's to stop me soldering this in place? I could weld it but it would be very difficult to make sure it was completely fuel tight. Solder on the other hand would flow nicely into all the gaps and cracks if the metal was nice and shiny.

I suspect the answer will be that vibration on the fuel tank could cause the solder to crack (basically a dry joint) which could then leak fuel out. But I'm interested to know what others think. Of course an alternative would be brazing but I don't have anything that will get that hot.

Cheers, Paul.

Lotus Esprit [meaning] a 1:1 scale Airfix kit with a propensity to catch fire

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Bottom line for me Paul ius that you have invested a HUGE amount of time and no doubt cash in this project.

Dont scrimp on anything to do with fuel or electrics or you might just end up watching your pride and joy go up in smoke the week after you finish it. :devil:

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I've just had a new bottom welded into mine, cut out old one and cut new one and weld in, hey presto....

Mark

Flush tank out lot and lots with water before welding.. Did I say lots?? and lots more....

Mark MacKenzie  Elise S2 135 Sport 

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I've just had a new bottom welded into mine, cut out old one and cut new one and weld in, hey presto....

Mark

Flush tank out lot and lots with water before welding.. Did I say lots?? and lots more....

Did you weld it yourself? What sort of welding did you use mig/tig/arc/gas?

Paul.

Lotus Esprit [meaning] a 1:1 scale Airfix kit with a propensity to catch fire

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Also consider finishing the inside of the tank with a chemical coating (Frost's do one).

They're designed to stop leaking tanks leaking, but I think they would also give a great protection against rust, which forms at the base partially due to water being more dense than petrol.

Oh yes, my tank appears to have started failing, having just put the gearbox back in, I'm not happy.

Andy

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Yes, I'm going to cut the bottoms out and then have them blasted inside (the outside's already done). Then as you say paint the inside with the stuff from Frosts - including the new bottom that I'm going to make. Normally, people just pour the suff in the filler pipe and slosh it around but I want to make sure that every part of the inside is covered. Then weld the bottom on and paint the outside. I don't know what type of welding would be more suitable though?

Paul.

Lotus Esprit [meaning] a 1:1 scale Airfix kit with a propensity to catch fire

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I've just had a new bottom welded into mine, cut out old one and cut new one and weld in, hey presto....

Flush tank out lot and lots with water before welding.. Did I say lots?? and lots more....

Apparently the best way to do this is to connect the empty fuel tank up to a diesel engine and let the tank fill with diesel fumes for ten or fifteen minutes. Dont know the chemical reaction or anything but I was told this by a professional welder who repaired a fuel tank for me once. We connected it to an old diesel Landrover for a while and it didn`t blow up when he welded it but at your own risk etc etc.

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Not sure about painting the bottom of your tank then welding it in place. Wont the paint just catch fire or at best melt leaving your tank unprotected inside. I thought the whole idea about pouring it in and sloshing it about was to try and form a complete skin inside the tank thus providing additional protection from it leaking. I have just ordered the kit from frosts as Im replacing both tanks in my S1. I couldnt find a Left Hand one so bought a V8 tank and cut 70mm from the middle and had it mig welded back together at the local welders who also mentioned filling the tank with carbon monoxide from a running exhaust (NO MATTER HOW LONG ITS BEEN STANDING FOR). I had to mod the fuel transfer outlet from the RH tank so that it was the same diameter (25mm) as that of the V8 tank. I mig welded a new pipe into the tank and then soldered around the weld to be sure there were no leaks (fingers crossed). Sloshing frost kit next week hopefully..

Phil

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There's probably a very good reason why I shouldn't do this and I think I know what the answer is but I'll ask it anyway... If I cut the bottom off my rusty fuel tank and just leave a 0.5" flange all the way around and then cut a piece of sheet steel to fit the bottom of the tank which butts up against the flange what's to stop me soldering this in place? I could weld it but it would be very difficult to make sure it was completely fuel tight. Solder on the other hand would flow nicely into all the gaps and cracks if the metal was nice and shiny.

I suspect the answer will be that vibration on the fuel tank could cause the solder to crack (basically a dry joint) which could then leak fuel out. But I'm interested to know what others think. Of course an alternative would be brazing but I don't have anything that will get that hot.

Cheers, Paul.

Hi Paul

I have welded quite a few VW fuel tanks for buggies and kit cars, all I did was empty the tank, leave it in the sun for a while to evaporate all the residual fuel, pour in a litre of cloudy ammonia, slosh it around for a while, cut the tank as necessary, then weld it up with the Oxy Acetalene.

Never had a drama, but I always poked an oxy flame into the filler from the other side of a wall to be sure, before starting with the angle grinder.

You would have to seal the openings up to hold the ammonia in upside down, I did this with plastic & gaffer tape.

We found this a lot easier than the car exhaust way.

Wear goggle or your eyes will smart.

B) ..............xisab

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Never had a drama, but I always poked an oxy flame into the filler from the other side of a wall to be sure, before starting with the angle grinder.

Too late I've already cut the bottom out with an angle grinder!! The tanks had been empty for the best part of a year and were as dry as a bone. I take the point about vapour but I just can't see there being enough vapour left after a year to ignite. Next step is to get the insides blasted and then cut some patches for the bottoms. I'm going to get the bottoms seam welded on using TIG and then solder over the top of the weld all the way around just to make doubly sure.

Paul.

Lotus Esprit [meaning] a 1:1 scale Airfix kit with a propensity to catch fire

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