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Thread: Fuel Tank Leak?

  1. #11
    Senior Member
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    Default Re: Fuel Tank Leak?

    Quote Originally Posted by JoeRuscito View Post
    ...from the factory... "Yes we are using the new sealant and yes you should be fine.. You installed according to the directions.

    You will get sealant residual in the system and therefore a good practice is to clean the inline filters after about 10 hours of operation… Also be sure to sump the header tank.. especially the first fuel runs.. "
    WOW is all I can say to that! Out of curiosity what brand is this new blue goo? Likely solvent based if it needs to sit open. If so, some are not compatible with alcohol (ethanol). I'd do some research.

    YMMV, Greg

  2. #12
    Senior Member jiott's Avatar
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    Default Re: Fuel Tank Leak?

    I also say WOW! What if someone uses it that way on a fuel fitting downstream of the last filter. The residual could easily clog up the very small jets and orifices in the carburetors. Its been awhile since I read thru the FAA publication on recommended practices for aircraft construction and maintenance, but I believe pushing sealant into the fuel system is totally against their directions.

    The stuff Kitfox recommends is Permatex Permashield 85420 Gasket Dressing and Sealant. When you read the application directions it says nothing about threads, but talks only about gasket and flange surfaces. It is specified as being fuel, ethanol resistant.

    Personally, I will continue to use it by applying to the male thread only and leaving the last couple of threads bare.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  3. #13
    Senior Member efwd's Avatar
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    Default Re: Fuel Tank Leak?

    If I may add my 2 cents worth. I didn't deliberately place this sealant to the tank threads first but I did apply it to the fitting threads and installed it. I found that I was not holding air in the tank via the balloon on the cap vent tube. I removed and reinstalled the fitting about three times, each time I reapplied the sealant to the male threads. By then I had residual sealant on the tank threads and it did end up sealing up. I fully expected to find debris within the fuel system and as I have stated before the only stuff I found (still finding it a bit) was the little white granuals that resemble sand. Because of this finding during fuel samples, I have removed the large fuel filter and cut it open. I found absolutely nothing in that filter. I think at the 100 hr I will change the inline filter I have coming off the header tank. I suspect that that is where all the debris might be. Either that or the sump drains are doing a fine job at capturing it and Im purging it on fuel sampling.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  4. #14
    Senior Member jrevens's Avatar
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    Default Re: Fuel Tank Leak?

    Interesting. My instructions specifically specified Permatex 80938 (9AR) for this. I recently had to remove one of my tank quick drains and asked John at Kitfox what they now used. He said it was the 9AR. It is creamy white in color as opposed to the blue 85420 you guys are talking about. I think that the 9AR has possibly been discontinued by Permatex, but I was able to get a new tube on Amazon, at a ridiculously high price. Threading and sealing a metal fitting directly into a tapped fiberglass hole is potentially problematic, and there should be a better way. If I was starting over, I believe I'd drill and tap the tanks oversize, then bond brass threaded reducer bushings into the tanks with a structural epoxy. A metal to metal joint on fittings that may have to be removed would be a much better design, IMHO. Better still would be to redesign the tanks slightly to allow that to be done while also providing additional clearance to better accommodate the metallic bushings.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  5. #15
    Senior Member JoeRuscito's Avatar
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    Default Re: Fuel Tank Leak?

    Guys I really appreciate all of the input, not that I feel any better about the situation as a whole... I think I will simply have to diligently check the filters through the first hours. Maybe to some extra time running on the ground before any flight takes place. My wonder remains, will everything that might release, release in the first few hours... or might I have a nasty surprise many hours down the line. I may scope the inside of the tanks/header tank with a camera just to see how much is in there...

  6. #16
    Senior Member jiott's Avatar
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    Default Re: Fuel Tank Leak?

    I built my whole kit using 9AR on every tapered threaded fitting including fuel, brakes, oil and coolant and have had zero leaks for 740 hours; I like the stuff. However I recently used it up and bought the blue 85420 which I have not used yet. My understanding was the 9AR is no longer available and Kitfox factory has been selling the 85420. I always used the 9AR by putting it only on the male thread, but don't remember what the actual instructions on the tube said. I believe the 9AR was also described as a gasket/flange sealant rather than a thread sealant.

    I understand from this forum that many folks have been using Loctite thread sealants on their projects with apparently good results (those thread sealants instruct you to apply only to the male thread). My own hesitation in using them is that they cure to a hard non-flexible condition which is fine for metal to metal fittings torqued to proper tightness. But for a metal fitting into fiberglass where the torque value is extremely low I want the non-hardening sealant that remains flexible and of course is compatible with ethanol containing fuel. My 2 cents.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  7. #17
    Flying Felix's Avatar
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    Default Re: Fuel Tank Leak?

    Hello everyone,

    Have you thought of researching Hylomar Universal Blue? It does not harden and it works well with various fuels. Might be worthwhile to look into it.

    Happy flying!

    Flying Felix

  8. #18
    Senior Member Dave S's Avatar
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    Default Re: Fuel Tank Leak?

    Per John's comments - exactly what I found to be true.

    Permatex 9AR was re-branded Permatex Tack & Seal Gasket Sealant Item # 80938; and, the tube clearly has 9AR in parentheses following the Item number 80938.

    It's the same stuff; or, similar enough to be indistinguishable in physical characteristics or uses.

    Business just loves to rebrand stuff.





    Quote Originally Posted by jrevens View Post
    Interesting. My instructions specifically specified Permatex 80938 (9AR) for this. I recently had to remove one of my tank quick drains and asked John at Kitfox what they now used. He said it was the 9AR. It is creamy white in color as opposed to the blue 85420 you guys are talking about. I think that the 9AR has possibly been discontinued by Permatex, but I was able to get a new tube on Amazon, at a ridiculously high price. Threading and sealing a metal fitting directly into a tapped fiberglass hole is potentially problematic, and there should be a better way. If I was starting over, I believe I'd drill and tap the tanks oversize, then bond brass threaded reducer bushings into the tanks with a structural epoxy. A metal to metal joint on fittings that may have to be removed would be a much better design, IMHO. Better still would be to redesign the tanks slightly to allow that to be done while also providing additional clearance to better accommodate the metallic bushings.
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  9. #19
    Senior Member JoeRuscito's Avatar
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    Default Re: Fuel Tank Leak?

    Quote Originally Posted by Danzer1 View Post
    WOW is all I can say to that! Out of curiosity what brand is this new blue goo? Likely solvent based if it needs to sit open. If so, some are not compatible with alcohol (ethanol). I'd do some research.

    YMMV, Greg
    This is the blue goo in question:

    https://www.amazon.com/Permatex-Perm...a-585235998177

    It does state that it is resistant to ethanol.

  10. #20
    Senior Member Maverick's Avatar
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    Default Re: Fuel Tank Leak?

    Would someone describe what the banjo fittings are or show a picture of these. I'm not familiar with this term.

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