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Fuel resistant sealing compound?

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by titus, Jun 15, 2015.

  1. So, I replaced the unreliable OE fuel pump on my KTM with the recommended solid state unit, and to do this I had to make up an acute bend in the line, using three brass corner pieces. I used 'fuel resistant' tape provided by an auto shop on the threads of the brass pieces, and it all went together nicely.
    Six months later the joins are weeping fuel. Not a flood, but enough to be a worry.
    My question is - what PROPERLY fuel resistant compound should I use to seal the bits and pieces this time?
    It shouldn't need to be pulled apart again so can be permanent.

  2. #2 oldcorollas, Jun 15, 2015
    Last edited: Jun 15, 2015
  3. I think the Loctite is a pressure curing sealant like threadlockers (as it is methacrylate ester based) but with Teflon to allow disassembly, and to aid in fuel resistance

    oh, for permanent you ned something that will cure in place.
    some 1pack epoxy paints are fuel resistant but may not sure in a joint
    eg http://www.kbs-coatings.com.au/product/gold-standard-tank-sealer/
    and the POR stuff
    some say JB weld will work... but in joints, may not cure or take a long time to cure

    for permanent, cure in-joint, possibly fuel tank epoxy? :D
    for example, http://www.caswellplating.com.au/store/store.php/products/epoxy-fuel-tank-sealer
    I can't remember the name of the 2-pack stuff i used years ago (it ended up a grey colour). could have been this?

    it also depends on what the joints are and how they are supposed to seal.
    if they are non-parallel threads, I'd go with the 567, as that's what it is designed to do.
  4. Thanks OC. There's no particular need for it to be permanent, just to not deteriorate over time.
    I had some 5699 lying around but that was for a different job. It looks like the 567 is the go.
    If not, I'll encase the bastard in JBWeld :LOL:
  5. sealing from the outside is also a valid method :D works for radiator tanks (don't forget the Chux superwipes for reinforcing :eek: )
  6. There are oil and/or fuel resistance gasket pastes. "Repco".
  7. Um, yeah. Auto stores ain't autostores, Sol...
  8. 3bond.
  9. 1104 seems to be the one that specifically mentions fuel, or is there any other?
  10. check threebond.com
  11. #11 oldcorollas, Jun 15, 2015
    Last edited: Jun 15, 2015
    which one? (edit) 1104 looks like "rubber"
    silicones are not really compatible with fuel, and their anaerobics look like normal threadlockers? are they ok?

    has fluid compatibility chart on P38/39
    for gasoline/petrol, 567, 565, 569, 545, 577, 542, 565, 243, 263..
    some are faster cure, have different chem resistance etc

    567, slow cure, good chem resistance, 204C
    565, rapid cure, general purpose, 150C
    569, for hydraulics
    545, pneumatic/hydraulic, small fittings, easy to assemble and remove

    looks like their normal anaerobic threadlockers are also fuel resistant too?
    mebbe try medium strength locker, and see if it leaks in 6 months :) (says here 100% strength after 5000hrs with fuel)
  12. What about good old fashioned Permatex Form-a-gasket No1?

    From http://www.permatex.com.au/_product...ermatex+Form-A-Gasket+No.+1+Sealant-1296.aspx
    Fast-drying, hard-setting sealant designed for sealing rigid materials and flanges, or patching holes and joints where permanent assembly is desired. Temperature range -54C to 204C; resists common shop fluids and fuels.

    Suggested Applications: Freeze plugs, threaded connections, manifold gaskets

    Edited to add;
    I presume you are talking threaded joints, if so I see no problems with the Permatex, no need to go to exotic or high tech solutions for a problem that has been around for as long as petrol fuelled motor vehicles have.
    ie, no need to reinvent the wheel.
    • Like Like x 1
  13. sound similar to the old "STAG jointing paste/compound" ?
    probably ok as long as it actually dries in the threads (alcohol evaporation to cure)., otherwise you might rely on the outer dry bit to do all the sealing?

    wonder if you can send a baggie of white paste in normal envelope? :D (I have a tube of 567 that will last me for life)
  14. Thanks OC, but I'm pretty sure I can get hold of 567 locally.
    My experience with Permatex has only been with oil-tight applications, not fuel, so I was wary. And we also have the added complication of (some) ethanol now being added without notification.

    I think some of these products are a bit gooey and gummy to be easily used on threads, but I'll grab a couple and see how we go. At least the problem is upstream of the pump so there is no pressure involved.
    • Like Like x 1
  15. #15 gunissan, Jun 15, 2015
    Last edited: Jun 15, 2015
    Being cautious is only being sensible. (y) It is most certainly oil-tight, and fuel-tight with good-old-fashioned petrol. I've used it for this myself.

    Good point, cautious again, I'm with you. I've got no clue how ethanol proof Permatex might be. Maybe an email to the company might be enlightening?

    Edit to add;

    Some light reading for those who might be interested.

    It's a thick liquid, similar to other thread sealing compounds used elsewhere, so with reasonable care (small amounts) when applying I think a neat result is certainly possible. Nevertheless, your bike, your call.

    Good luck.

    oldcorollasoldcorollas I've not come across that Stag stuff before. Have you used it yourself?
  16. yup, smells great :D
    is sort of non-hardening.. ish.. so that you can separate parts later.. and now that I look back into fog of memory, I did use it on (car) carbies..
    is not like a glue.. more like.. tar...
    is the sort of stuff an old English mechanic might use on MG's :D (that's my image)

    checking MSDS's suggest they are not so different (I learn new stuff everyday ;9 ).. but the permatex may have higher pine resin to pigment ratio = less viscous when "dry"?

    Permatex is:
    mostly kaolin (clay) ~55%
    "rosin" (pine tar/resin) ~25%
    isopropyl alcohol as a solvent ~15%
    plus other non-important stuff (TiO2, castor oil, emulsifier) <5%

    Stag is:
    "pigment" (could be anything, like clay or TiO2) ~30-60%
    Pine tar (rosin) ~ 5-15%
    Shellac + ethanl solvents, 10-20% each (that's why it smells good :D )
    +other crap <5%
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    • Agree Agree x 1
  18. #18 oldcorollas, Jun 15, 2015
    Last edited: Jun 15, 2015
    looks like it! functionally the same.
    differences could be due to permatex improving the formula and being made in a factory, and stag is mixed in black cauldrons to the same recipe as in the dark ages? :D (ie, made from mixing Bug and Tree resins ;) )

    only functional difference may be rate of hardening due to volatility difference between IPA and ethanol.. and slight stiffness difference between shellac and pine tar

    "alcohol" would be used for cleanup of both
  19.  Top
    • Like Like x 1
  20. nothing wrong with a scientific threadjack ;)

    well.. just looking up properties of rosin..
    it's the sticky stuff left over when you distill out the turps....
    so it's obviously soluble in turps.

    also said to be soluble in alcohols (again, obviously).. but IPA vs ethanol.. same resin, same effect, I'd suggest same susceptibility to the alcohol functional bits
    dichloromethane/chloroform too (just in case you have any lying around ;) )

    also soluble in benzene and toluene... and potentially other aromatics... which is a problem for petrol..
    so basically unleaded is various naptha fractions, and aromatics... and rosin is soluble in all of them..
    then again, the sealant stuff is majority clay, but I wouldn7t rely on it for a pressure situation where fuel could be forced into it

    also, TG/melting point of rosin is around 70-80deg... so probably not so good with engine heat..

    dry some Permatex stuff, then see if you can clean it off with petrol? :D still might be ok in thin loaded flange type joints