<VV> Fuel leaks, and threaded fasteners

kevin nash wrokit at hotmail.com
Thu Sep 27 23:39:18 EDT 2018

Regarding the original post on fuel system leaks: it is ALWAYS a good idea to put some sort of thread sealant on pipe threads, as it otherwise takes an incredible increase in torque to reliably seal the connection, this is because the roots and crests of the mating threads have to bottom out to seal, otherwise they will leak there. Somewhere at the Parker Hannifin sight they illustrate this leak path with a sectioned pipe thread connection, and list the difference in torque required to seal those kind of connections when dry and when a sealant is used. Randy is correct that for a low pressure connection, grease can work, although for me I was always a little "queasy" about putting goop of any kind in fuel system fittings, as I normally didn't want to take a chance on having that goop get into the fuel system... somehow. I would just grit my
teeth and tighten the fitting as tight as was reguired to not leak.
 Other fittings like flare fittings, of course, do not leak through the threads, and must be
sealed at the flare. I've found that the use of conical sealing washers really takes care of a lot of leak problems, without resorting to lots of thread torque... particularly when a high pressure fuel system is being used, like I am for my efi. Using the soft aluminum sealing washers has made it so easy to seal the connections  that the thought of putting "thread lubricant" on these connections never crossed my mind, as the torque needed to seal is so low, there's no real advantage to lubing the threads, even if it wasn't bad practice for other reasons.
 As for thread lubricant for other uses? DONT do it unless the instructions say so, period.
Kevin Nash
63 Turbo, EFI daily driver,
running one of the coolest
alternative Corvair cooling fans
the world has ever seen!

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