The International Cessna^® 170 Association

You guys will yell at me because i don't have the part number but mabe you can advise anyway. The fitting that mates the feul line to the carb purchased with the appropriate part number at great expense I realize now is leaking at the carb. It looks to me like a pipe thread going into the carb. Seemed to go in smoothly and with several test runs of the engine it didn't leak. Today I found a little gas definately leaking. Have you guys run into this and is it legal to put some sealer of teflon on the threads to seal it uP?????? Thanks G

It has been my experiance that depending on the mechanic teflon tape is OK but not with all of them. I've never seen any "offical" guidence either way at least that I can recall.

The problem that most mechanics have with it is that if not carefully applied a piece of teflon tape could be stretched over the end of the fitting and then either partially block the fluid flow or break of clogging at some other location causing restricted fluid flow.

From my totally unlicenced seat here in from of the computer I'd say that if indeed the fitting you are talking about is a tapered pipe thread then carefully applied teflon tape insuring no part of the tape extendes over the edges of the threads would be OK. When I occasionally use it I start the tape about a half thread from the end.

BTW there are are other forms of pipe thread seal and I've used them as well. Again depending on who is looking over my shoulder this OK. And again I don't start at the end of the threads so no sealing material can enter the fluid area.

parker fuel lube is the proper stuff to put on fuel line fittings.

Hey Tom. Perhaps you could tell us why Parker Fuel Lube is the "proper" sealant.

And if it's a "lube" why do you use it to seal?

Guys before you all go nuts on each other let me say sorry for my horrible spelling of "FUEL" thanks and carry on G

OOOOHH you where asking about a FUEL line. Well that is totally different.

I don't think we'll go nuts on each other I really want to know more about why and how Parker Fuel Lube is more exceptable than other forms of thread sealant.

You want fuel? Ask and ye shall receive.

Teflon tape should NOT be used as a thread sealant on petroleum lines.

OK that's great Blueldr but WHY.

Perhaps I know/knew this but that but that info must have gotten flushed to provide room for some other piece of useful information.

N9149A wrote:Hey Tom. Perhaps you could tell us why Parker Fuel Lube is the "proper" sealant.

And if it's a "lube" why do you use it to seal?

Parker fuel lube is a alcohol based grease, that petrol products will not desolve. And it will allow the fitting to be taken apart.

Use it very sparingly do not get any on the first thread of any fitting.

use a tiny bit on your primmer plunger and the "O" ring will be there many years, and the plunger will operate smoothly.

Parker fuel lube, you old army / navy guys will know it as "Gas Tight", "Grease- Valve plug" It was formulated for the assembly of fuel systems during WWII, it has a mil spec, and it works.

proper stuff to use? You bet.

Thanks Tom I appreciate that explanation. I would seem there isn't any question that Parker Fuel Lube is an acceptable sealant and lube for aircraft use.

I'm still hoping that someone could tell us why you shouldn't use teflon tape or the liquid teflon seal on aircraft pipe threads. Of course it can't be used to lube O rings or fuel valves.

I've often thought this is sealant thing might be on the lines of Mogas verses Avgas or to use MMO or not discussion. Perhaps the use of Parker Fuel Lube exclusively is a hold over from before teflon tape day's and teflon tape has not gained expectance in the A&P tool box for no other reason than A&Ps are taught to use the fuel lube.

The best reason not to use "teflon" tape or sealant on fuel fittings is because it will shred into tiny fragments when the threads are screwed together, and fine particles of the tape may clog/interfere with carburetors and fuel injectors. The "paste" type of "teflon" sealants also contain tiny fragments of the synthetic and will do the same thing.
If you don't have "Fuel Lube" then use of Permatex No. 2 is acceptable substitute...again with the caveat not to get any on the first one or two threads. (Permatex is approved for aviation use. No. 2 is non-hardening. No. 1 will harden.)