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enter image description hereHi there, I have a 1965 VW Beetle (in Australia) that I am trying to repair. To get it running, it just seems that I just need to repair two holes at the bottom of the fuel tank (it is leaking petrol/gas). Are these holes part of the design (they don't look like the result of damage)? Is there parts associated to filling these holes?

Does anyone know what part I need and how (and where I could get it from Australia) to plug these holes?

Thanks in advance!

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    I think you got your money's worth out of that tank. Might be time for a new one. Corrosion might have dug hundreds of thin spots in that tank and these are the two that happened to rust through- the whole tank bottom might be dangerously thin. Might want to have the tank ultrasounded to look for more thin spots.
    – Harper - Reinstate Monica
    Commented May 25, 2022 at 23:28
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    I've used POR-15's fuel tank repair to good effect before now, but on tanks that were hard to come by. If a replacement is easy for you I'd just replace it
    – Caius Jard
    Commented May 26, 2022 at 18:18
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    I vaguely remember that old fuel tanks were protection against corrosion by the fuel itself. So if it has been without fuel for a long time, you will have to check that the fuel tank doesn't have any more "weak spots". Fuel dripping out of the front of the VW and getting transported by the headwind towards the hot engine in rear...doesn't sound like very desirable.
    – Klaws
    Commented May 27, 2022 at 11:08

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Those holes are not meant to be there. This photo of a new tank doesn't have the holes. The holes look like someone has drilled into the tank to remove the fuel at some point. Whether that was to steal the fuel or just to get the fuel out before getting rid of the car.

It probably isn't worth repairing since replacement tanks are readily available, but with suitable safety precautions taken to avoid explosions, it should be possible to braze or solder a patch over the holes.

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  • Soldering's a good idea - I didn't think of that as an option. Need some seriously large soldering iron for the job, and probably some lead-based solder and flux.
    – Criggie
    Commented May 25, 2022 at 7:36
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    @Criggie No need for a soldering iron, just a propane blowlamp will heat the area to solder. Just need to take precautions against explosions. I also have an old fashioned large copper soldering iron that is pre-heated by a blow torch which could be used for this.
    – HandyHowie
    Commented May 25, 2022 at 7:42
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    I'll double down on with your suggestion to have "suitable safety precautions taken to avoid explosions" ... CANNOT be too careful in this department.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented May 25, 2022 at 12:57
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    @paulster2 Yes, I didn't describe how to do this, because I don't want to make it sound less dangerous than it is. Just wanted to highlight the risk of an explosion.
    – HandyHowie
    Commented May 25, 2022 at 13:32
  • I would purge the tank of vapours by mostly filling it with water, but that's a great heatsink and it will also steam up and pressurise the tank making the patchwork harder. The answer is likely to use a really hot iron, a pre-tinned "patch" and to get on-and-off again quickly. Using a similar approach I once re-soldered a wire to a rear-window defroster without damaging the glass.
    – Criggie
    Commented May 25, 2022 at 19:45
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Back in the day, it used to be possible (in the UK) to wander around a scrapyard and unbolt random bits off stacked piles of dead vehicles, and that was how I kept several cars going.

Fuel tanks though were almost always deliberately punctured by the scrapyard, using something pointy and sharp. Any residual fuel in there would then simply evaporate. There were several safety reasons for this.

  • The fuel system doesn't tend to vent much, so any fuel in the tank stays in there. Ditto fumes.
  • Dead vehicles were usually stacked several high. It's easy to rupture the fuel system (in any number of places) when dropping one car on top of another.
  • People salvaging parts aren't always careful to avoid damaging the fuel system or ensuring leakage of stray fuel is avoided.
  • Even in the absence of other sources of damage, rubber/plastic fuel lines would simply deteriorate and leak.
  • Larger parts were often removed with cutting gear, presenting the risk of heat or sparks to ignite anything combustible.
  • With lights, mirrors and other shiny surfaces, there's a risk of just the sun causing hot spots which would light off anything combustible.

And from a "consumer" point of view,

  • You've no idea whether the tank on a dead vehicle is damaged or not until you fill it up with fuel, which isn't safe.
  • A fuel system exposed to the air will corrode on the inside, causing rust particles to clog up your carbs/injectors.

Generally it wasn't in a scrapyard's interests to open themselves to all these problems. An old screwdriver rammed through the fuel tank solved it fairly quickly and neatly.

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Are you sure those are the only holes? Looks like at some time there was water in the petrol, and it sank to the bottom (petrol floats) so it rusted away the steel, and someone (you?) has cleaned the rusty edges up. Look for pinholes, perhaps use air pressure and soapy water while blocking all the normal holes.

Welding a fuel tank is not recommended - you'd need to purge and the whole thing with inert gasses or water, but welding near water will make a lot of heat which is steam that interferes with the weld.

The common repair is a 2 part epoxy like JB Weld, which claims to be petrol-resistant. It is hard because you don't have any access to the inside.

I'd go with a thin stainless steel patch, which is completely "glued" to the tank with well-mixed epoxy, and a well-prepared surface on the tank and the patch. Then another layer of epoxy on the outside once the first one has set completely. You might choose to use some fibreglass or other structural cloth as an intermediate layer.

Some people use fibreglass, but it may not be fuel-proof. Check the labels before buying anything.

Your other options are a used tank from a donor car, or a brand-new reproduction tank. Check locally for a VW specialist who can advise.

You might prefer a new plastic or aluminium tank, perhaps with better mounts or more capacity, or more crash-damage resistance.

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    I'm with you on this, it's possible to fix but if it's started to rust out it's likely to continue. @TerrenceJ, you can patch this but it may not be a lasting fix.
    – GdD
    Commented May 25, 2022 at 8:00
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    Does the tank have internal baffles? If not, the 60mm opening on the other side gives some degree of access to stick a flat object in to spread the JB weld on the inside. Seems like it'd be awkward but doable.
    – Dan Is Fiddling By Firelight
    Commented May 25, 2022 at 15:17
  • @GdD yeah if its rusted on the inside there are tank treatment chemicals that can be added and sloshed around to "set" any established tinworm, and then vented. Finally there's other products that will place a plastic-like liner layer inside the fuel tank. Both of these work better with a tank that has its holes patched already, so a little chicken-and-egg. A replacement tank is best, but probably most expensive option.
    – Criggie
    Commented May 25, 2022 at 19:41
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Do not weld gas tanks unless you know what your doing! Its best to solder the holes with a BIG solder iron very hot. I have fixed a lot of tanks. I use copper sheet or copper pennys to solder over the holes. Just use a good flux, any tin/lead solder should do. pre tin the patches and tank. that way you can see if its clean enough for solder to flow over the area. if not, wire brush it and try it again with more flux.

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  • Those holes are clearly not part of any engineering design, in the factory or as any retrofit… if they were, they'd be both round and evenly placed. At risk of being called ignorant I wonder why, in this day and age, guys here don't think think there are several adhesives that will happily and much more safely take the place of welding or soldering. At risk of being boring, I've read of several cases where welders really did kill them themselves by exploding their tanks… not text-book scenarios but real cases.
    – Robbie Goodwin
    Commented Jun 2, 2022 at 18:52

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