NPT Fitting Sealants & Brake/Fuel liquids

[Phil]

I know the AN fittings go on dry, but do NPT threads in the brake system (such as the ones going into the the Matco Parking Valve) get any type of sealant or lubricant like thread tape, Teflon paste, etc??

I'm not sure how brake fluid might react with the tape or paste.

Same thing for fuel on NPT fittings that have fuel flowing through them.

Thanks,
Phil

[Mel]

I use Permatex "form-a-gasket" on all NPT threads.
Been using it for over 50 years. Never let me down.

[dedgemon]

Hey Mel,
Would that be 1, 2, 3, aviation, ... ???

[Phil]

I went to buy some from ACS and ran into the same question...

1,2,3 or Aviation...

[Mel]

That would be "2, non-hardening pliable sealant"! Aviation or not shouldn't matter.

[Phil]

Perfect Mel....

It's on my next order with Spruce. Nice to have the same stuff for Brakes and Fuel...

Thanks again,
Phil

[mcencula]

I thought I had read (can't remember the source...maybe in Van's manual) to use fuel lube on NPT fittings. Is that right or am I remembering incorrectly?

[G-force]

All NPT fittings require a sealant on the threads. By design, there is a small gap between the root and the crest of the threads. In use, it is good practice to clean out, and reapply sealant anytime a fitting is removed or disturbed. In practice, I have found if you need to tighten a fitting a little bit well after it was first installed to clock it, there is not a problem. If you need to loosen it, it is better to pull it all the way out, reapply sealant, then tighten to the orientation you need. If it too loose at this point, go another whole turn tighter. While all thread sealants are called "non hardening", they do take a set or cure, hence the advice to apply fresh sealant if you need to disturb a previously installed fitting. Some sealants like the Permatex #2 mentioned above use solvent evaporation (alcohol) that evaporates to "cure" the joint. Others like Loctite 565 or 567 are anaerobic. The nice thing nowdays with the internet, the technical data sheets of most any product are easy to find. One important data point to look at when choosing a thread sealant is if it is compatible with the fluid or gas in the system you are working on.

Locktite 567: http://www.rpiparts.com/ds/56707tds.pdf
Permatex #2: http://www.permatex.com/documents/td...tive/80015.pdf

[Mel]

Originally Posted by mcencula

I thought I had read (can't remember the source...maybe in Van's manual) to use fuel lube on NPT fittings. Is that right or am I remembering incorrectly?

Fuel lube is certainly another option. I've just used Permatex for about 50 years and it works.
The important thing is that all NPT fittings need some type of sealant.

[carl nank]

Fuel lube did not work for my brake lines. I could not get it to stop leaking due to having to clock the elbows around the brake pedals. I think I will try the #2 permatex.

The fuel lube did work well with the fuel lines, but, I did not have to cloc them.