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Author Topic:   Proper Thread Sealer for Fuel Fittings
lucky 13 posted 04-08-2004 12:10 PM ET (US)   Profile for lucky 13   Send Email to lucky 13  
I just installed a fixed fuel tank under the console of my 15. I purchased a brass hose barb which threads into an aluminum socket. I would think that a thread sealer would be required here. Can anyone tell me which type is suitable for sealing threads in a gasoline system?


Is 5200 fuel resistant when dry? I need to seal under the fuel fill fitting to prevent water intrusion.

Thanks in advance.

kglinz posted 04-08-2004 12:21 PM ET (US)     Profile for kglinz  Send Email to kglinz     
Teflon tape.
SMLWhaler posted 04-08-2004 12:54 PM ET (US)     Profile for SMLWhaler  Send Email to SMLWhaler     
kingfish posted 04-08-2004 12:57 PM ET (US)     Profile for kingfish  Send Email to kingfish     
At the ACE hardware I frequent, they have plain old teflon tape (white) for typical plumbing connections, and a colored teflon tape (yellow or pink, I can't remember) that is specifically intended for use around petroleum products. The latter would be my recommendation.
SS17 posted 04-08-2004 01:07 PM ET (US)     Profile for SS17    
Teflon tape will work, but causes a lot of engine problems when it is wrapped onto the first thread too much and small strands end up in the fuel system. If you use it don't wrap it onto the first thread. Fuel separator instructions recommend pipe sealer made for gasoline contact, but I use the tape and it works.
Montauk posted 04-08-2004 01:09 PM ET (US)     Profile for Montauk  Send Email to Montauk     
White teflon tape is not reccomended for fuel lines, it will dissolve from contact. It can be used if you are very careful and hold it back from the end so it does not dissolve into the fuel line and plug your carburetor.
PFSQUAN posted 04-08-2004 02:09 PM ET (US)     Profile for PFSQUAN  Send Email to PFSQUAN     
Use PermaTex, which is specifically designed for this use.
jimh posted 04-09-2004 01:38 AM ET (US)     Profile for jimh  Send Email to jimh     
An excellent question, and even more amazing answers. I had no idea of the special yellow Teflon tape. I'll look for the Permatex product, as well.
lucky 13 posted 04-10-2004 11:15 PM ET (US)     Profile for lucky 13  Send Email to lucky 13     
I was in Home Depot buying a couple of SS hose clamps as I was a few short. I overheard the "plumbing specialist" who was helping a guy with a natural gas hose (for a dryer or stove I assume) discussing the use of yellow teflon as opposed to white for this application. However, I don't think I am going to use either for the fuel line. I think that the permatex is what I need. I have looked at permatex in a few stores, but none of the tubes indicated suitability for fuel applications. I'll try an auto parts store.

I seem to recall learning somewhere that teflon was not a sealer and that the threads have a tapered interference fit (which creates the seal) and the teflon is used as a lubricant to allow the fitting to be tightened with less resistance. Can anyone confirm this? If this is correct, then any teflon would work.

Thanks for the input.

whalerron posted 04-11-2004 12:08 AM ET (US)     Profile for whalerron  Send Email to whalerron     
Do not use teflon tape in an application where it will be in direct contact with gasoline. I searched for a long time for a product which was suitable for gasoline line fittings. The local NAPA dealer told me that the only product he knew of for this application is

Permatex Aviation Form-A-Gasket Sealant Liquid
Permatex Part #80019
NAPA Item #765-1210

- Ron

Tom W Clark posted 04-11-2004 01:23 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
I use Permatex "PIPE JOINT COMPOUND" Part No. 51H which is a thick black tar-like joint compound.

The label says it " a semi-liquid, universal seal for hot and cold water, steam, illuminating gas, propane gas, butane gas, natural gas, lubricating oils, fuel oils, gasoline, gasoline vapor, kerosene, ethylene glycol, glycerine and other liquids and gases."

About $3 for a 4 ounce container. Works for me.

ShrimpBurrito posted 04-11-2004 02:19 AM ET (US)     Profile for ShrimpBurrito  Send Email to ShrimpBurrito     
I discovered the white / yellow Teflon tape phenomenon awhile ago, but never realized the white would dissolve on contact. However, I am now left with this question: if yellow can be used with gas, it presumably can also be used with water and everything else. Seeing as how they are the same price, why do they even make the white any more?
jerseyron posted 04-11-2004 12:18 PM ET (US)     Profile for jerseyron  Send Email to jerseyron     
This question has come up before. For many years I had used white teflon tape on auto fuel fittings without a problem. Prior to installing a racor filter on the boat last year, I put a piece of the tape in a jar of gasoline and left it for 48 hours. There was NO disintergration or breakdown of the tape. If there was going to be a problem,think it would have happened during that time frame.
kingfish posted 04-11-2004 12:30 PM ET (US)     Profile for kingfish  Send Email to kingfish     
The yellow teflon, besides (presumably) a different chemical composition, is thicker or at least stiffer than white teflon, by feel. I've used the yellow teflon a lot around gasoline fittings, it has performed well, and is not all that difficult to assure loose shreds don't get loose inside the fuel lines. I've usually got permatex around too, but for some reason usually reach for the teflon. Less messy, maybe...
catadromous posted 04-12-2004 11:27 PM ET (US)     Profile for catadromous    
Some engine manufacturers specifically recommend against using Teflon tape on fuel fittings. So do some filter companies. As I understand it, the problem with Teflon tape arises after a few cycles of assembly and disassembly. The Teflon gets shredded and pushed into the fuel lines after a couple of cycles. Rebuilders of diesel injector pumps find little strands of Teflon tape in pumps that have 2 micron filters just upstream. You guessed it, Teflon tape on the fuel filter nipples is often the culprit.

Several of the goops recommended in this thread are good choices, but Iíll add my favorite. Gasoila NT (non-Teflon) by Federal Process. Itís a non-hardening pipe thread sealant that is compatible with gas, diesel and gasohol blends up to 15% ethanol. They also make a varnish type that does harden. This is used a lot in aviation, but I donít think it is recommended where gasohol is used.

Save the Teflon tape for water systems.


linust posted 04-14-2004 12:13 PM ET (US)     Profile for linust  Send Email to linust     
Permatex has a number of products designed for exposure to fuel. Here's the one I've been using:

for a few other possible threadlockers, see

BTW, I've learned that these liquid-based threadlockers/sealants work better than teflon tape for sealing air tool fittings (disconnects for air compressor, lines, tools). With teflon tape, I'd get a certain amount of leakage that would drain off enough air to start up the compressor after a few days of inactivity. Not so with the sealant.

lucky 13 posted 04-16-2004 10:08 AM ET (US)     Profile for lucky 13  Send Email to lucky 13     
Thanks for all of the input. I used Permatex Form-a-gasket. The tube specifically states that it can be used in gasoline systems. It has the consistancy of tar and its brownish in color.
allen723 posted 08-06-2005 01:21 AM ET (US)     Profile for allen723  Send Email to allen723     
teflon tape...when used for gas means natural gas not fuel gas. the white tape is for water.. the yellow tape is for natural gas not gasoline. Tell me if I am wrong.
allen723 posted 08-06-2005 01:30 AM ET (US)     Profile for allen723  Send Email to allen723     
the white is also used for air.

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