Someone school me on pipe thread plugs please

[someotherguy]

Tried googling it and the confusion level just got worse, LOL

The replacement water neck on my 7.4 has a spot for a 1/2" pipe plug, as I guess some applications call for a sensor to live there. Application notes on some of the water necks listed on Rock have this note: "May Require 1/2-14 Npsf DrySeal Plug (# 444746)" that "NPSF" and "DrySeal" are what caught my eye.

The suggested plug has a Dorman cross of 090-002 which on Rockauto says - it's NPT. I'm having a hard time wrapping my head around it seems like there's NPSF and NPTF and they are obviously different. NPSF uses an o-ring to seal? NPTF should seal from the interference fit of the taper.

Is it just an error on the Rockauto listings where it calls the thread NPSF, and they really mean NPTF ???

The reason it matters to me is I'm wondering if I can rely on this plug to seal the hole in the water neck without any thread dope/tape. I don't want to go crazy tightening it because it will certainly crack the cast aluminum.

Richard

 

[454cid]

Not really answering your question directly, but here goes.

I'm not familiar with any o-ring seal pipe thread, but I'm no expert, either. If I recall correctly, there is a "regular" pipe thread, and a more precise pipe thread that is supposed to seal without tape/sealant.

When I last bought plugs for my truck, it was for the oil cooler elimination, and I found some US made plugs at Fastenall, that didn't look like they had been molded by children out of Play-doh. I don't recall what standard they adhered to, I put pipe dope on them. The two I mentioned earlier screw together just fine, but mismatched I'd assume you may not get the benefits of the no sealer.... I didn't care, as I was going to use it.

I think in the case of cast aluminum, I'd use pipe dope just so I didn't feel the need to crank it down too tight, as you mentioned. I don't see any reason not to use pipe dope. Most of that stuff, is rated for all kinds of pressures, fluids, and materials. It doesn't have to look sloppy, either.

I would not use tape.... I hate that stuff.

 

[someotherguy]

The straight thread stuff uses an o-ring because there's no taper. That's why it confuses me that the Rockauto listings say NPSF which is straight thread, but the plug they recommend is NPT, tapered.

And yeah, I'll almost surely install it with some pipe dope, as long as my jar of it hasn't gone funky. It's been forever since I needed it.

Richard

 

[RichLo]

I'm also no expert but when I get confused about pipe fittings or any other odd union of any kind, I go to McMaster and play around in their website until I find an answer.

But if you already have the water neck and plug and they fit together without that cross-threading feeling I wouldn't worry too much, I'm sure it was a typo. Every o-ring vs NPT that I have encountered is either way off or has that uh-oh feeling when you start threading.

 

[PlayingWithTBI]

Let me throw something in that's probably totally useless in this case. Electrical conduit thread is the same pitch as pipe thread but, is straight instead of tapered. That's all I know

 

[Komet]

I think this site covers the basics about the differences:

Understanding NPT, NPTF & NPS Thread Connections

Understanding NPT, NPTF & NPS Thread Connections - Learn more about various pipe fitting thread connections to ensure proper selection to create leak free seals.

www.buyfittingsonline.com

Easiest solution is to just buy the recommended part:

Genuine GM OEM 444746 Plug | eBay

Find many great new & used options and get the best deals for Genuine GM OEM 444746 Plug at the best online prices at eBay! Free shipping for many products!

www.ebay.com

It looks like just a normal NPT plug to me. You could maybe find it a little cheaper but as I have found out, sometimes it's difficult to buy just one pipe plug.

 

[someotherguy]

Yeah, I found that same page, the issue is that Rockauto's site recommends a part # that is an NPT item but in the recommendation text describes it as NPSF.

Check it out, in both the GPD and GM Genuine listings: https://www.rockauto.com/en/catalog...ystem,thermostat+housing+/+water+outlet,10337

For the plug, GM # 444746 crosses directly to Dorman # 090-002 which is what I bought, but for only $1.75 instead of $15+ for the GM part. It's just a pipe plug; I'd hope Dorman can get it right, but you never know!

Richard

 

[454cid]

Yeah, I found that same page, the issue is that Rockauto's site recommends a part # that is an NPT item but in the recommendation text describes it as NPSF.

Check it out, in both the GPD and GM Genuine listings: https://www.rockauto.com/en/catalog...ystem,thermostat+housing+/+water+outlet,10337

For the plug, GM # 444746 crosses directly to Dorman # 090-002 which is what I bought, but for only $1.75 instead of $15+ for the GM part. It's just a pipe plug; I'd hope Dorman can get it right, but you never know!

Richard

Oh, that really is a pipe plug similar to what you'd find at Lowes. What I bought uses an Allen wrench, so it doesn't stick way out. I can certainly understand not wanting to spend $15.

 

[Schurkey]

First Guess: The actual problem is relying on the misleading RockAuto web page.

 

[someotherguy]

Is it just an error on the Rockauto listings where it calls the thread NPSF, and they really mean NPTF ???

First Guess: The actual problem is relying on the misleading RockAuto web page.

Trust me, it was obviously a consideration from go

Thankfully the truck is back together, running, and the cooling system appears to be more or less pressure-tight for the moment. I say "for the moment" because it still needs a lower radiator hose (probably), the coolant bypass hose from intake to water pump looks like hell, the heater hose connection on the intake is MIA and appears blocked off with some plastic-y crap, so I'll have to also assume the heater core is likely no good. Have yet to identify what they used to plug the radiator end for the heater hose. I fear each new thing I touch on this truck just leads to the next headache. I'm still amazed it made the 200 mile trip home from buying it.

Richard