Lister D de-soldering fuel tank

Hi,
    I have a lister D fuel tank, condition isn’t to bad, except I have two large deep dents, that require flattening out.
  My first thought was to just just fill them, but as there pretty deep, 1/2” in depth and 4“+ or so wide, That’s a lot of filler!
   I did read some where, that it is feasible to de solder tank, folding back outer to gain access, then tapping dents out, then re soldering.
  Has anyone done this, seems a bit of a performance but I’d rather attempt it, than use huge quantities of filler! Plus I do have the time, and soldering skills
Option 2, attempt to pull them out, but that may require drilling holes, as metal thick
 Your thoughts much appreciated
  Mark

Can you push them out as much as possible with a bodywork 'spoon' via the filler hole and then finish off with filler?

Hi,
I’ve tried a few times to push them out via filler, but a lot of resistance due to thickness of metal, and the dents are at other end of tank and awkward to push on them from filler

Mark,

I make my own tanks to the same design, I would suggest you remove the end cap nearest the dents and use a bodywork spoon or similar lump of suitable metal, don't unsolder the main body as you may loose its shape. The tanks are soft soldered together.

Maryalice

Hi,
Yes that’s what I plan to do, remove end cap and attack it from there, I’ve also uncovered a few pin holes some a little larger, think there solderable, and I will seal tank once done

While in the tank get a patch of copper sheet and cover the holes with it by soldering in place, then put a thin skim of filler on the outside just to fill the holes. I use emersion tanks copper as it's thin and easy to use.

Thanks, yes I like the idea of a copper patch on the back, I shall do that!
Cheers