NPT Thread sealant?

[HotRodHudson]

I need to install the heater hose pipe into my sbc water pump. In non automotive applications I use Teflon Tape or pipe dope but I’m not sure what to use in this NPT thread automotive application. Products I have are in the pictures below.

 

[Noltz]

I've used Teflon on nearly this exact application before. 4.3 intake heater ****** broke & I was tasked to replace it. I still have the tap from cleaning up the thread.

Standard white teflon.

 

[Katzen]

One more vote for Teflon tape. I’ve used it many times in applications like that. There are also automotive specific pipe/plug sealants out there too. I prefer Teflon tape, as it assures the sealing agent stays on the threads.

 

[nadogail]

Teflon Tape applied correctly for the win. The liquids and pastes can migrate throughout the system.

 

[64C10]

I usually use Loctite 565 for cooling system fittings. I’ve pulled enough Teflon tape out of hydraulic systems that I won’t use it for anything anymore.

 

[Wrench97]

Any of the pipe dopes will work just fine, I too have stopped using tape after finding pieces of it where it should not be.

 

[rustyjames]

The Permatex #2 has never let me down.

 

[Walkers]

If you want to crack the water pump housing, then Teflon tape for sure! It is Not a sealant, it simply lubricates so you can squeeze those tapered threads in tighter than you thought you could. Right stuff, silicone, or any pipe sealant will work fine. To be clear Teflon tape works fine, but the chances of you over tightening it exceed 100%.

 

[rlitman]

If you want to crack the water pump housing, then Teflon tape for sure! It is Not a sealant, it simply lubricates so you can squeeze those tapered threads in tighter than you thought you could. Right stuff, silicone, or any pipe sealant will work fine. To be clear Teflon tape works fine, but the chances of you over tightening it exceed 100%.

Teflon tape IS a packing sealant (and it works as well on valve stems as it does on NPT threads). Yes, it does lubricate too. Using torque as the hard limit for plumbing tapered fittings is just plain dumb however, but if you work like a gorilla, sure, you'll crack some things.

To my eye, that is a steel fitting with rolled threads. Rolled pipe threads (I mostly encounter those on copper fittings, but the issues are similar) tend to have poorly shaped threadforms that seal poorly without heavy application of a thick sealant. If it were me, I'd fill the threads flush with my thickest pipe dope. Then warm it with a heat gun until it starts to bubble, let it cool to an even thicker state, and wrap with 3-4 turns of pink teflon tape starting at the second thread. Finish by using your best judgement as to tightening. What I'd suggest to guide this is to hand fit the fitting dry, count the number of turns it goes in, and then when doped up, turn it to there plus 2 more turns and see how it feels.

As for teflon tape getting into a system, it will never do that so long as you follow two simple rules.
1) Don't tape the leading thread, and
2) Use a dental pick to remove the coils left behind when you take a fitting out.

 

[blazemaster83]

I too have steered away from tapes. I use this stuff at work called Fastseal ATS.

FasSeal-ATS™ Anaerobic Thread Sealant with PTFE

fedpro.com

 

[Wrench97]

Teflon tape IS a packing sealant (and it works as well on valve stems as it does on NPT threads). Yes, it does lubricate too. Using torque as the hard limit for plumbing tapered fittings is just plain dumb however, but if you work like a gorilla, sure, you'll crack some things.

To my eye, that is a steel fitting with rolled threads. Rolled pipe threads (I mostly encounter those on copper fittings, but the issues are similar) tend to have poorly shaped threadforms that seal poorly without heavy application of a thick sealant. If it were me, I'd fill the threads flush with my thickest pipe dope. Then warm it with a heat gun until it starts to bubble, let it cool to an even thicker state, and wrap with 3-4 turns of pink teflon tape starting at the second thread. Finish by using your best judgement as to tightening. What I'd suggest to guide this is to hand fit the fitting dry, count the number of turns it goes in, and then when doped up, turn it to there plus 2 more turns and see how it feels.

As for teflon tape getting into a system, it will never do that so long as you follow two simple rules.
1) Don't tape the leading thread, and
2) Use a dental pick to remove the coils left behind when you take a fitting out.

It's the removal process that usually leads to tape contamination of the system.
Water pump fitting on a SBC is a low pressure application a little pipe dope is all that is needed to seal, most of the time they have nothing applied and seal fine.

 

[64C10]

As for teflon tape getting into a system, it will never do that so long as you follow two simple rules.
1) Don't tape the leading thread, and
2) Use a dental pick to remove the coils left behind when you take a fitting out.

Don’t rely on procedure alone. The different chemistry and additives found in systems can attack the tape, and you end up with whole new problems. Hydraulic oils will turn it into a bubble gum-like substance that migrates throughout the system until it finds a passage to plug.

Knowing how many different alcohols and solvents have been put into things in the name of “the environment”, it’s become a gamble to use the stuff on anything but a domestic water line.

 

[HotRodHudson]

It’s good to hear everyone has found the product that suits their needs, which hopefully means I’ll get it sealed up without issue. When I first tried it I only went around the male threads 3 times w/ my Blue Monster Teflon tape. It didn’t feel like it was sealing well and it screwed in too far as the Teflon back edge wasn’t visible before it was tight enough. So I pulled it apart, cleaned old tape out with a pick & wrapped it 5 times with a tiny bit of the Permatex thread sealant on the outside of the Teflon tape, just a a safety measure. This time I counted my turns & I was a little over 1 turn beyond dry fit. I didn’t gorilla tighten it but did get it gud’entite! The pipe was steel but the water pump housing was aluminum.

I’d read that if the pipe was really pitted guys will put a little Permatex #2 or Permatex thread sealant on the pipe ****** then slip the hose on & tighten it. They say it had sealed up leaking connections. I’ve only ever used some Sil-Glyde on the pipe end to help ease the hose over it but it’s a good idea.

The only time I’ve used Permatex thread sealant with PTFE was on some stainless steel bolts on my 37 Hudson’s side cover/water jacket. I’ve no idea why but it didn’t hold & I had leaks past the threads. An old timer told me to try thread locker like Loctite Blue 242 & it worked like a charm! I can see why Loctite 565 was recommended.

 

[ez-duzit]

Stay away from Teflon tape for most uses. Use LeakLock.

 

[ChevyEFI]

I never had a problem with Teflon tape in cast or alloy and water pumps. I also never had a problem with the permatex teflon paste in a tube (super common at parts stores.) A friend who was meticulous about his (and hers) cars turned me onto paste 20 some years ago when it was a new(er) practice and could be had in a tube at the dealer counter.

 

[jsaw]

I like to use Teflon paste.

 

[rlitman]

Don’t rely on procedure alone. The different chemistry and additives found in systems can attack the tape, and you end up with whole new problems. Hydraulic oils will turn it into a bubble gum-like substance that migrates throughout the system until it finds a passage to plug.

Knowing how many different alcohols and solvents have been put into things in the name of “the environment”, it’s become a gamble to use the stuff on anything but a domestic water line.

I'm calling BS here. The few chemicals I am aware of that will attack teflon without also dissolving metal lines will eat through any other elastomers (rubber or polymers) long before they damage the teflon. In fact, teflon is called for in may hydraulic seals for just this reason.

 

[64C10]

I don’t know the chemistry of it, nor do I claim to. I do know for a fact though that the regular old plumbers teflon tape will turn into gum in a hydraulic system from having had to remove it, especially from suction screens. Also given that the added thickness has been known to crack castings, I prefer something that allows for tighter tolerances. My opinion only.

 

[zmotorsports]

I steer clear of any teflon tape products. Probably from my years of working on hydraulic systems.

I use either Loctite 565 or the one I really prefer is ARP's thread sealant.

 

[Black300zx]

About the only automotive NPT thread application that I've had issues with are when a single-wire sensor is involved that needs to ground through the threads to the block in order for the sensor to work properly. Never had any leak issues, just electrical issues.

A couple examples on my Z:
*Oil pressure sending unit - Teflon tape can prevent it from grounding properly if excess amounts are used
*Coolant temp sensor for the dash gauge - Teflon tape can prevent it from grounding properly if excess amounts are used
Liquid thread sealant in these applications allows the threads to make contact and ground properly.

For a waterpump pipe like this, I'm sure a number of different methods would all work well.

 

[Walkers]

Teflon tape IS a packing sealant (and it works as well on valve stems as it does on NPT threads). Yes, it does lubricate too. Using torque as the hard limit for plumbing tapered fittings is just plain dumb however, but if you work like a gorilla, sure, you'll crack some things.

To my eye, that is a steel fitting with rolled threads. Rolled pipe threads (I mostly encounter those on copper fittings, but the issues are similar) tend to have poorly shaped threadforms that seal poorly without heavy application of a thick sealant. If it were me, I'd fill the threads flush with my thickest pipe dope. Then warm it with a heat gun until it starts to bubble, let it cool to an even thicker state, and wrap with 3-4 turns of pink teflon tape starting at the second thread. Finish by using your best judgement as to tightening. What I'd suggest to guide this is to hand fit the fitting dry, count the number of turns it goes in, and then when doped up, turn it to there plus 2 more turns and see how it feels.

As for teflon tape getting into a system, it will never do that so long as you follow two simple rules.
1) Don't tape the leading thread, and
2) Use a dental pick to remove the coils left behind when you take a fitting out.

What I can tell you for certain is that I have a scrap bin full of high dollar hydraulic valves, pumps, automotive parts, etc, that were brought in to see if they could be welded up after being cracked while installing pipe threads using Teflon tape. It just makes it way to easy to tighten, and the fittings never feel tight.

 

[Wrench97]

Realistically a steel pipe screwed into a aluminum automotive pump housing should seal without any thing on it if tightened correctly.
I see plier teeth marks all over that ******.

 

[ez-duzit]

Realistically a steel pipe screwed into a aluminum automotive pump housing should seal without any thing on it if tightened correctly....

No. It needs sealant.

 

[HotRodHudson]

Yep, teeth marks from before my working on it. I spray painted it flat black again & then installed it.

 

[Mandres]

I use plain old blue loctite. For low pressure fittings it works great. For 3k psi+ hydraulics I use the special hydraulic/pneumatic formulation

 

[slowtwitch73]

I got some of that Leak Lock... smells purddy. I keep it with my other good smelling stuff like WD40 and Tri Flow,

 

[rjn2649]

Another vote for leak lock, used to use that stuff on stainless pipe fittings, it was the only stuff that worked.

 

[Firebrick43]

Locktite 565 works, 545 is better. I hate leaklock, it sets hard, eventually cracks, and leaks. And then a royal pain to clean off.

 

[ez-duzit]

...leaklock... eventually cracks, and leaks...

No, it doesn't

 

[Willie Makeit]

Loctite 545 or 565, dependent upon application. As stated before, Teflon is not a sealant. It is a lubricant.

 

[slowtwitch73]

As stated before, Teflon is not a sealant. It is a lubricant.

^^ I think everyone knows that.

Teflon TAPE is a 'deformable filler'.. the Teflon aids in getting the threads tight, many times sealed.

 

[Willie Makeit]

^^ I think everyone knows that.

Teflon TAPE is a 'deformable filler'.. the Teflon aids in getting the threads tight, many times sealed.

You'd be surprised how adamant some are about incorrect information.

 

[rlitman]

You'd be surprised how adamant some are about incorrect information.

Like yourself. Here's the word from the manufacturer:

Scotch® Thread Sealant and Lubricant Tape 48​

• Principally used as a pipe thread sealant.
• Rolls on dry, permanently seals joints and at the same time provides lubricant so the joint can be opened with ease at later date

 

[Monza Harry]

Like yourself. Here's the word from the manufacturer:

Scotch® Thread Sealant and Lubricant Tape 48​

• Principally used as a pipe thread sealant.
• Rolls on dry, permanently seals joints and at the same time provides lubricant so the joint can be opened with ease at later date

In my nearly 40 years of building moulds, all with elaborate cooling [or heating] systems that are almost always removed for "Engineering Changes" there isn't any visible "sealant tape" left in the threads pipe sealant [Loctite and Permatex are prevalent here] but there is tape through out the system and like here "everybody has a theory and insists theirs is the right one" I read the manufacturers instructions and follow and compression tools frequently use heated oil [not all steam and electric heating is also used] for thermoset plastics and it reacts with the tape and requires redoing with "Pipe Dope"! Personally I LOATH TAPE. Harry
Here is a a little light reading for those inclined This covers pipe plugs (threads starts on page 24) and pressure plugs for those that don't believe that there are 2 different tapers to fittings. [Oh and screws as well]

http://www.unbrako.com.au/images/downloads/engg_guide.pdf

Harry

 

[kwb]

Rectorseal #5

Seems to work for me and I like saying rectorseal.

 

[American Locomotive]

Teflon tape is a sealant. It gets squished in the threads and blocks the fluid path. Standard NPT threads do not have the correct geometry to seal, and there will almost always be a leak path through the threads without something to block it. I've seen plenty of situations where an NPT fitting without tape was almost bottomed out and still leaked, when taking it apart, taping it, and putting it back together had it sealed with just a few turns.

..but these days, I prefer Loctite 567 to tape.

 

[Willie Makeit]

Like yourself. Here's the word from the manufacturer:

Scotch® Thread Sealant and Lubricant Tape 48​

• Principally used as a pipe thread sealant.
• Rolls on dry, permanently seals joints and at the same time provides lubricant so the joint can be opened with ease at later date

I base my opinion on engineering, not marketing. believe as you see fit.

 

[rlitman]

...This covers pipe plugs (threads starts on page 24) and pressure plugs for those that don't believe that there are 2 different tapers to fittings...

We've been down this path here before. NPTF has the same taper as NPT, with the difference being in the deformable threadform. However, NPTF is not the only dry seal thread system, so perhaps you're right? I dunno, because that has NOTHING to do with NPT thread sealant or this conversation/thread in general.

I base my opinion on engineering, not marketing. believe as you see fit.

Sure, YOUR engineering is better than 3M's. Un huh.

 

[American Locomotive]

I base my opinion on engineering, not marketing. believe as you see fit.

...and NPT threads by engineering definitions are not designed to mechanically seal. There are NPT threads you can bottom all the way out until there is no more thread left, and they still won't seal. If the root and crests of the threads never interfere, there will always be a leak path.

NPTF threads on the other hand have tightly controlled major and minor diameters and are designed to seal without sealants.

 

[Willie Makeit]

Sure, YOUR engineering is better than 3M's. Un huh.

Yes, I'd say NASA's engineering is better than a company that sells products for a living.