748 Tank Leak

Discussion in 'Technical Help' started by Roadtrip, Sep 4, 2024.

  1. Noticed a slight weep coming from the drain bolt so replaced the bolt and washer and topped up with a bit of fuel only to notice its still weeping, then removed a bit of paint,

    You can see its coming from the edge where the drain plug meets the tank metal, a few mm of a darker half circle which is the petrol, There is no bubbling of paint or rust so i can only assume it might have rusted a bit inside around the drain plug, no movement of drain plug when i tighten the bolt up and the bolt seals perfect,

    Whats my options,
    Tank sealer or is it possible to weld around the outside of the plug but it is very close to the fuel pump base plate or the inside and would there be enough room for a welder to get to it with the base plate removed, another tank?


    Anyone else heard of it leaking around the plug before.

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  2. Not sure tank sealer would be successful. I'm going to go seriously off the wall and suggest silver solder using an old fashion iron that you heat separately. Andy
     
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  3. I thought Tig welding is the way forward but some electrical or plumbers solder is a good shout and worth a try. If you get it hot enough to flow and if there isn't any paint stuck in the groove it going to work.
     
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  4. Thanks all for the ideas much appreciated :upyeah: would sooner go the welding/solder route, then have the fun of fitting a new O ring to fuel pump base plate :)
     
  5. Silver solder has way too high a melting point not far off brazing temperatures. Using it would destroy the paintwork for several inches around. If it is cleaned properly and with a good flux, lead solder will work although it will need a substantial soldering iron to get enough heat at the joint as the tank will act as a massive heat sink
     
  6. I’d give Belzona a try. Clean the area well and seal around the drain plug. Its a durable metal repair and resistant to most chemicals
     
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  7. I also use PTFE tape on the threads...just to add to the overall security of sealing everything properly. :upyeah:
     
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  8. i had this problem a few months ago, around a mount

    the sealant repairs are temporary at best, dont waste your time, they sound good on paper (and cheap),

    if its around joint get it brazed, they put a heat dam around it to stop the heat doing damage, obviously the tank was empty, i think they have a fan blowing air in while they do it.

    cost me £160, but hard to find some one local to do it, luckily its hidden, so i did a good paint repair

    you can see its a pucka solid job, won't be a problem again

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    #9 southlondonCBR, Sep 5, 2024
    Last edited: Sep 5, 2024
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  9. Looks a nice job do you have a link for them
     
  10. It was a fella in Hastings
     
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  11. Don't Goggle "Looking for a Fella in Hasting"
     
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  12. Showed the tank to a fabrication firm today who cleaned up the area a bit more and will do the job with a Laser welder, never heard of one myself,
    A few date stamps

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  13. Laser welding is really cool. Literally, keeps the heat very localised.
     
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  14. I've just been reading up a bit about it...I thought the technology wasn't really in use yet, and the videos were kinda bullshit...It could be a real breakthrough for the home builder. :upyeah:
     
  15. It's been around at least 20 years. We had some stuff laser welded back then but it was very specialized. I'm not sure if it's much good for proper structural welding yet. I stick to Tig for now.
     
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  16. I asked about the paintwork and he said exactly what you said and paint loss about a centimetre around the plug? a thin bead all around the plug which will help as its very close to the fuel pump base plate,

    Fingers crossed it works and there isn't anymore problems with the surrounding area o_O if so he can fix it :D
     
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  17. i'm being lazy not reading all the comments, but have happily "soft-soldered" many car and motorcycle steel fuel tanks** over the years, and as long as there is no underlying corrosion "pickling" still going on/still about, then it's permanent if done properly*. Lancia chose to soft-solder outlet and return pipes on some of their '60's and '70's cars and i've never had a problem with them leaking as a result of that process, again, if done properly.

    * does depend on the application, i'm sure many of you know, and it's probably covered above, but it's all about adequate surface area (like brazing and similar).


    ** ditto water radiators and heater matrix, i used to enjoy it.
     
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  18. Dropped the tank off this morning and just picked it back up,
    The chap who does the laser welding said he couldn't laser it as setting it all up and with the shape of the tank and paintwork ( up side down) in the machine would not be the best option, so they tig-mig ? weld instead, next job leak test :splat: Nice clean job with minimal paint damage £30 well spent.

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  19. Looks a nice neat job.
     
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