Big argument...er discussion. When ***embling fuel fittings (br*** non-AN) do you use (I never have) pipe dope, teflon tape, anything at all? I don't recall ever having a leak in any fuel lines (or brake lines for that matter) after ***embling with no 'stuff'. The "rocket scientists" out at the hangar (there were no AIs or A&Ps in attendance that day) say ALWAYS use sealant of some kind. What do the tried and true rodders say? tnx dwj
I had to use it on my chrome fuel pressure gauge to the chrome fuel line into the carb. There was no way those were going to seal without it...
I can't say that I never have doped a br*** fitting, that would just be a non-truth. I try not to but if it doesn't seal I dope it. In a perfect world a br*** fitting would not leak and they say you should avoid teflon or pipe dope on br*** or aluminum, because of the friction coefficient. Pretty easy to split a br*** ort aluminum fitting. Sometimes they lack perfestion. For instance I have an old intake that I out br*** fittings into the water p***age. The old intake is cast iron and the threads are not perfect. I had to pull the fittings and tape them to keep them from leaking. I never tape them up front and on anything with a small orifice in the system I am extremely carefull.
I think the teflon tape isnt reccomended because a little piece will cause big headache if it comes loose. At the wrongest time of course. DONT ask how I know. Sealing goop will melt and go through, hopefully, without causing any grief. Chrome on Chrome wont seal without an agent. From "hanger" I ***ume airplane. Use what they do.
I use fuel resistant teflon tape and put it a thread back from the end so none can get into the system. I also use the teflon sealant in a tube sometimes. Something that I do that is never recommended is that I put sealant around sending units going into the intake. I know everyone says you will not get a good ground but I have always sealed them because I have gotten seepage around the sender when I didn't do it. Never had had a problem with the sender grounding either as I think the sharp edges of the threads cut through the sealant and metal touches metal anyway in some spots when you tighten the sender down. I use an ohm meter to confirm I have contact between the sender and intake. Don
I do a lot of work on hot water pressure washers[up to 3500 psi]the factory uses blue loc-***e on all pipe threads.works great and doesnt plug nozzles etc.
All NPT threads are designed to be used with a sealant. For metal to metal seal NPTF (dryseal or AKA National pipe thread-fuel) thread form should be specified. Here's a quote from the machinerys handbook (AKA the bible of metalworking): American National Standard Dryseal Pipe Threads for pressure tight joints Dryseal pipe threads are based on the U.S.A. (American) pipe thread; however, they differ in that they are designed to seal pressure-tight joints without the necessity of using sealing compounds. To accomplish this, some modification of thread form and greater accuracy in manufacture is required. The roots of both the external and internal threads are truncated slightly more than the crests, i.e., roots have wider flats than crests so that metal to metal contact occurs at the roots and crests coincident with, or prior to, flank contact. Thus, as the threads are ***embled by wrenching, the roots of the threads crush the sharper crests of the mating threads. This sealing action at both the major and minor diameters tends to prevent spiral leakage and makes the joints pressure tight without the necessity of using sealing compounds.
My latest is teflon tape on the sender for a fan. The threads cut through the tape and the only place the tape resides is in the loose spots.
I use teflon pipe dope on tapered thread pipe fittings, including senders. I don't use it on flare nuts.
If I remember correctly Pipe Dope is not only a sealer but a lubricant so the threads don't gall and release for repairs.
After 5 years of apprentice school as a steamfitter, I always use pipe dope of some sort on tapered NPT threads. We were taught that it is indeed a lubricant to allow the tapered threads to tighten deeper forming a better seal. I like the teflon tape when used correctly. One wrap is all that is necessary. It really doesn't fill any voids. When it first came out it was very expensive compared to the brushable pipe dope and the boss would get pissed if we made several wraps knowing that most of it ended up outside of the joint sealing nothing.
Hangar "Rocket Scientists" HaHaHa... Every airport has them! Usually only useful for consuming large quan***ies of Coffee or Soft Drinks, Lame Aviation Advise, Ignoring 43.13 1b and/or the MX Manual, but mostly noted for bumming Tools, Hardware, Chemicals, Airplane Rides or Lunch from you! Where would Aviation be without them? Everyone has their own favorites, but I have found that Fuel Lube/EZ Turn works good on pipe threads, and as a Model A Fuel Valve Lubricant... Any flare (Inverted, AN, SAE) is ***embled dry... Never use Teflon Tape around Fuel or Hydraulics... Loc***e makes some good products for High Pressure Hydraulics... Oxygen needs special sealant...
never use teflon tape on a brake line or fitting. i use pipe dope or 1 wrap of teflon tape on most other fittings,it can't hurt so why not.
One way to look at this argum....discussion is to consult the warranty card that comes with your rebuilt carburetor. As far as I know, every carburetor rebuilder or manufacturer will void all warranty if teflon tape is used on a carburetor fitting. If you just have to put something on (tapered threads ONLY), a drop of blue loc***e will do the trick; and if you use blue, it will come apart without damage. Jon.
well, it would appear that the answer is yes on NPT, no on flare fittings. AI of renown agrees....once I told him what the HAMB said... I do like the blue Loc***e® on tapered suggestion. thank you all for your learned and sagacious responses. dj
The flare itself is the seal on flare fittings. Fluid should never reach the threads... inverted or straight. If it does you have a faulty fitting or flare. Teflon tape on flare nuts looks so stupid proving that the mechanic does not understand where the seal actually takes place.
Blue RTV works o.k., but lately Ive been using Permatex 59214 High Temperature Thread Sealant. Good stuff, just takes a little, turns semi-hard. I would never use Teflon tape anywhere on a car. Dangerous stuff to use on fuel lines, lube lines or anywhere a piece of Teflon might plug something. I dont use plumbers pipe dope in the garage either.
The Jalopy Journal
