Another vote for Locktite 567 here.. whatever you do, don’t use fuel lube as a sealant! Too many people have, and it works for a little while, but it’s a lubricant, not a sealant, and eventually, it will leak, and the next person has to take apart every fitting and reseal it!
Good 'ole Aviation Form-a-Gasket (brown Permatex) is hard to beat...but there are dozens of choices.
I thought you weren’t supposed to use anything on npt seals except the torque of the fitting. What am I missing?
I thought you weren’t supposed to use anything on npt seals except the torque of the fitting. What am I missing?
Form-a-Gasket #3 is a non-hardening resin sealant. It doesn't form solid chunks, and dissolves with plain isopropyl alcohol.
https://www.permatex.com/wp-content/uploads/tds/80019.pdf
567 is an anaerobic methacrylate adhesive, the same family as Loctite/Permatex threadlocker products. It cures to a solid, and dissolving it requires a Loctite solvent.
https://datasheets.tdx.henkel.com/LOCTITE-567-en_GL.pdf
https://datasheets.tdx.henkel.com/LOCTITE-SF-768-en_GL.pdf
Mostly we use aluminum fittings, sometimes in tight places, so increasing the removal torque isn't a plus. It's already too easy to round the flats, and they're often screwed into fragile things. In addition, female threads should be cleaned before reassembly, so old sealant isn't pushed into the fluid line.
Like Bill, I too have some 567 in the sealant bin for specific applications, and yeah, it's good stuff. However, it's rarely used for anything I may want to take apart in the future.
I thought you weren’t supposed to use anything on npt seals except the torque of the fitting. What am I missing?
Thanks for posting the link Bob
I think that is the very same article that was used as research reference when the NPT fittings sealing recommendations chapter was added to Section 5 in the construction manuals.
This is a great explanation. The one thing I did notice that is different than the reference I think I’ve seen on Van’s site is the amount of tightening past finger tight. If I recall correctly, the Van’s reference said 1/4 turn past finger tight, whereas the link above says finger tight plus 1-2 turns. Is the difference aluminum vs steel?
I think you may be confusing the B nut that is on a flared line fitting versus NPT threads.
There is a difference between the two.
You have to use sealant on NPT (Tapered Pipe Thread), otherwise it will leak.
Permatex #2 and/or Locktite 565 (or 567 or 592). Apply sealant 2-3 threads from the "front" (opening) of the nipple.
In a previous thread (no pun intended), everyone was all about 565 for keeping the threads sealed, especially fuel drains. This thread is all about 567. What are the differences and where are each used? Are they interchangeable? Curious (confused) minds want to know.....
In a previous thread (no pun intended), everyone was all about 565 for keeping the threads sealed, especially fuel drains. This thread is all about 567. What are the differences and where are each used? Are they interchangeable? Curious (confused) minds want to know.....
Yup, the 565 is great.. 567 is the same with a higher temp rating.. I don’t think there’s a place where you NEED the higher temp rating, but it can’t hurt..
Which is why 565 is the one on the list of recommended sealants in Sect 5 (Par 5-27) of the construction manual.
I only bought the 567 over the 565 because that’s what Amazon had in stock at the time!