Welding a leaky diesel fuel tank

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webcraft

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OK, so now Avy-J's fuel tank has several pinholes along the welds.

Going to take it to a man to look at it on Thursday, but in the meantrime, any recommendations? There are a couple of places in Glasgow advertising.

- W
 
I replaced my leaking steel tank with a very nice plastic tank. OK, it was smaller at 91litres but I can motor for at least 24 hrs which is more than adequate for me. The original tank was about 180 litres.
 
For every pinhole that's evident, there'll be another five waiting to happen. I my experience the only sensible repair is a replacement, as suggested with a plastic one.
 
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Yeah, yeah . . . everyone says replace with a plastic tank, but the tank is specially shaped to fit in the lazarette and there is nowhere on the boat to put a rectangular tank of an equivalent size.

Holes are on the seams - what about a welding repair then using a liquid tank liner ?

- W
 
Just have a tank made to fit the space either in metal or ideally plastic. Nothing unusual about this.
 
Edwin at Alutec, at Creran Marine, in your neck of the woods, does a very good job, but it's difficult to pin him down.
 
NormanS said:
Edwin at Alutec, at Creran Marine, in your neck of the woods, does a very good job, but it's difficult to pin him down.
Click to expand...

The story of trying to get anything done in Argyll.

Perm any two only out of Available, Affordable and Competent.

Thanks though, will maybe try to get in touch.

- W
 
webcraft said:
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Yeah, yeah . . . everyone says replace with a plastic tank, but the tank is specially shaped to fit in the lazarette and there is nowhere on the boat to put a rectangular tank of an equivalent size.

Holes are on the seams - what about a welding repair then using a liquid tank liner ?
Click to expand...

There's a fair chance that the welds have corroded because they were badly done. I was told by someone who inspects welds on critical systems for a day job that the most common failing is using a rod of the wrong material. So there's a good chance most of the tank is fine and it'd just need those welds grinding out and re-done.

Make sure you find a welder who knows what rod should be used to re-weld.
 
webcraft said:
Nothing unusual about this for people with lots of spare money, but no way I can afford this.

- W
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Then you have to live with what you have got or can do. If it is so far gone that welding will not produce a reliable tank then you have two choices. First is fit the largest standard size (cheap-ish) tank you can find room for and tolerate the reduction in capacity or have one made to maximise capacity and fit the space available.

Just one of those many difficult choices when refitting an older boat on a limited budget.

You never know you might get lucky and find a wizzo welder who can repair the tank.
 
I had a tractor tank welded by someone who welded for Rolls Royce and as expected it was perfect. You need to be able to remove the tank to clean it out and get at it. He pressure tested it before replacement.
 
We have a 40 gallon S/S water tank. It started to leak, via pin holes in the welds along the bottom.
I took it to a welding shop here and asked them to re-do all the welds on it, which they did.
Brought it home, and pressure tested it with about 8' of water head - and pin jets of water were spouting in many areas!
I marked all these areas, took the tank back to the workshop, and asked them to re-weld again the areas that were marked.
Brought it home, pressure tested it again to 8' of water head, no leaks, hooray.
About a year later, more leaks...... this time I tried gluing plastic angles over the welds on the bottom with liberal amounts of 5200 (the American equivalent of the high bond strength Sikaflex) and this worked for about 6 months - then it started leaking again......
The tank is now looking for a new home. Or maybe a scrap merchant.
And one day I might even build a 'built in' tank of fibreglass panels to replace it in the bilge under the saloon where it was located.
 
You didn't say (or I missed it) what the tank is made of. Stainless or carbon steel?
If stainless, then weld attack is somewhat likely and especially when welded with the wrong filler material (as mentioned above). But in a stainless fuel tank the chance that the plate/sheet is pinholed is much lower than the welds being pinholed, and a re-weld is a good option to remedy.
If a mild (carbon) steel tank then the sheet being corroded is much more likely and the presence of pinholes might mean the whole tank is finished. Rewelding is possible, but only if there's enough "meat" to weld to.
I have a 316SS fuel tank and also water tank in same material. Both 45 years old, from when stainless was real luxury stuff! No leaks so far in either, but welding was done very competently.

When pressure testing, don't use too much pressure. A bicycle pump is enough. An air compressor might distort the tank. Spray a little soapy water on the outside of the slightly pressurised tank to detect tiny leaks, watching for the bubbles.
 
we used to have custom tanks made by obp motorsport for some of our vehicles. I would make a cardboard mockup, add the dimensions, and send them pics to build from. Less pricey than you might think, the last one was around £130, but it was a few years back.
 
I have made and repaired many tanks large and small.

I would TIG weld even mild steel. Grind back all the welds and then reweld ALL the previous welded joints.

Pressure test after is very important.

I have 3 built in mild steel fuel tanks in my mild steel boat hull and 2 stainless steel water tanks
 
Custom made plastic tanks are not mega expensive.
Sourced a tank via outfit on Ebay.
They made it up to my dimensions and with the outlets the same size/locations as the old one to fit existing hoses.
The beauty of any rigid plastic tank is that it has a bit of flex in it ,this enable me with bit of "coaxing" to get decent sized one into a location that would have been totally impossible with a metal tank of any description.
Probably lost a gallon or three in a 50 gallon tank.Price was 30% of prices quoted for S/S tank.
Real challenge was grinding up the old steel tank into small enough bits to get it out....hateful job ............................
 
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I think weldng an ali tank needs an expert with a TIG welder.
I would ask around motorsport places.
Plenty of race and rally cars have ali tanks for fuel and oil.
But 'aluminium' varies a lot.
 
Can you put diesel in an aluminium tank?

So a new tank is needed. Out with the West system manual, some Epoxy, marine ply and a weekends work to produce the goods. Send the photos taken to PBO and receive a nice thank you and cheque for the article which pays for the epoxy and plywood.

Pete
 
Pete7 said:
Can you put diesel in an aluminium tank?

So a new tank is needed. Out with the West system manual, some Epoxy, marine ply and a weekends work to produce the goods. Send the photos taken to PBO and receive a nice thank you and cheque for the article which pays for the epoxy and plywood.

Pete
Click to expand...

You could just laminate over the existing aluminium. Epoxy should stick well to ali.
 
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