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Fuel Tank Leak

Discussion in '365 GT4 2+2/400/412' started by Ferraridoc, Mar 7, 2020.

  1. Ferraridoc

    Ferraridoc F1 Veteran
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    Jun 20, 2012
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    I had previously fixed a fuel smell in the boot by noticing a slight discolouration in the insulation on the LHS tank (see "New 400i Coming" thread). There was a slight crack where some numpty had hit the top with a hammer or something, and two holes drilled by an even bigger numpty - probably mounting something on the boot board. I fixed both with epoxy.
    Today I get the car back from a service, and filled the tanks to the brim - the fuel smell was so bad, I almost threw up. It seemed to be from the right, so I pulled off the boot board and the RHS bumper tube. Photo coming...
     
  2. Ferraridoc

    Ferraridoc F1 Veteran
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    You can see the discolouration of the coating. I have started to strip it off where I think the leak is, expecting to find a seam, but there doesn't seem to be one there. Such a complex form must have seams - does anybody know where they are? Perhaps a diagram ot picture?
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  3. Ferraridoc

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  4. raemin

    raemin Formula Junior

    Jan 16, 2007
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    Lyon (FR)
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    Can'you try a tank sealer? If you tap the lower port, you could put the tank sidewise and properly apply the sealer?

    My brother bought some new uncoated tanks long ago (aluminium, flat black painted). these are in a rack 6980km away from were I am right now...could take some pics by the end of next week.

    By the way what's the use of the coating?
     
  5. Ferraridoc

    Ferraridoc F1 Veteran
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    I don't want to take the tank out at this point.
    I really hope that I've got the problem solved by then, but a few pics would be most informative, thanks.
    The coating protects the alloy, provides a bit of thermal insulation, and reduces condensation. Cold fuel on a humid day will cause condensation on the outside of the tank, which is... bad.
     
  6. raemin

    raemin Formula Junior

    Jan 16, 2007
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    R. Emin
    Does not protect alloy, as the "bare" tanks are painted, that's why I was considering using theses "as-is", but thanks for pointing out the condensation issue.
     
  7. samsaprunoff

    samsaprunoff F1 Rookie
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    Good day,

    On a side note about sealers... A colleague of mine has a friend that owns a specialty Industrial epoxy paint company and they use one of their paint products as a sealer for inside old gas (petrol) tanks for the old cars they restore. They mix the epoxy paint (2 parts), pour it into the empty tank, "swish" it around (they have minutes before the paint starts curing), then let cure for 24 hours. Effectively this seals any small pin-holes, etc that might have developed over time. The epoxy paint they use is virtually impervious to any chemicals, etc and the only way to remove it is via grinding, etc. Interestingly they have been doing this for over 20 years and have had no issues. Given that my tanks are empty I was thinking of doing this as well.

    Cheers,

    Sam
     
  8. Highmiler

    Highmiler Formula Junior

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  9. Ferraridoc

    Ferraridoc F1 Veteran
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    Thanks, Greg, but I can't find that thread. I'm trying to find a leak, which looks like it's along a seam from the wetness pattern, but it may be a single pinhole and the fuel has wicked through the porous coating. I'll check it again in a minute, and hopefully the wetness has contracted around the offending defect overnight. I'm hoping to seal it with a bit of epoxy.
     
  10. Ferraridoc

    Ferraridoc F1 Veteran
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    Thanks Sam. I'm hoping not to get to that point! My working hypothesis is a split along a seam, but I haven't found a seam where I thought there was one, hence the call out for info. I'll keep plugging away. Hopefully plug a small hole, fill up the tank (I've drained out 60 litres), and watch carefully - all in between helping my 10 year old build his P51 D Mustang!
     
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  11. Highmiler

    Highmiler Formula Junior

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    Here is the material I used.
    [​IMG]
    HighmilerFormula Junior
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    This patching compound is made by Flamemaster and is called "CS 3204 Class B Aircraft Fuel Tank Sealant". The paperwork says it meets MIL-S-8802F. The distributor and packager of this stuff is Located in Sun Valley, CA. Phone; 818-982-1650, Fax; 1-818-765-5603. I got mine from Van's Aircraft Supply in Oregon for @ $32.00 the quart..

    For those unfamiliar with Mil-Specs: these are stringent specifications produced by the US Military to ensure that what they buy is what the salesman claimed it to be. Most SAE Standards began life as Mil-Specs.

    Greg
     
  12. Ferraridoc

    Ferraridoc F1 Veteran
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    So I've scraped a bit more for the coating off, and noticed something curious: the stain on the coating isn't evaporating, and the little bits of stained coating don't have a petrol smell, in fact they're a little oily. Maybe somebody spilled something oily in the boot 20 years ago and stained the coating that way. Maybe I've been barking up the wrong tree. So I'm going to removed the rest of the boot lining so that both tanks are exposed, and then pour the petrol back in until it's brimming again, and watch closely. Should get to it by... April
     
  13. simon klein

    simon klein F1 World Champ
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    It's probably not much help but Marc found the source of my raw fuel smell in my 365, a couple of years ago,had to do with rubber fuel lines and breathers etc.
    He tells me that yours has sustained damage in that (RH) area of the boot....something to check out.
     
  14. SouthJersey400i

    SouthJersey400i Formula 3

    Mar 14, 2007
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    Ken Battle
    If no crack in tank the next obvious source after filling the tank is the seal on the fuel guage sender. I replaced mine and now have a lot less odor in trunk.
    Ken
     
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  15. Ferraridoc

    Ferraridoc F1 Veteran
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    Thanks, Ken - all options will be entertained. Hopefully it will be that simple.
     

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