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Thu May 08, 2025 6:39 pm

Hello...building a 1776 motor with a brand new AS41 case. Pulled out the lead plugs, drilled and tapped to put in NPT pipe plugs. Decided to use brass, since aluminum will likely round out should they ever need to be removed (especially the 1/16 plugs).

I've seen posts elsewhere about aluminum vs brass plugs, and recommendations for just about every kind of sealer you can imagine...but nothing mentioning loctite 518.

I don't want these to back out, and its supposed to be rated for temperature and oil where some other suggestions aren't. Being anaerobic, it may have some locking properties though not really a threat locker.

I'd like to hear from anyone who's used it, particularly with brass plugs?

Thu May 08, 2025 7:58 pm

I used 545 on my last set of brass plugs. Maybe I am wrong, but it worked well!

Thu May 08, 2025 7:59 pm

I have never in 50 some years had a pipe plug back out of an engine case. It just does not happen.

Thu May 08, 2025 8:04 pm

oprn wrote: I have never in 50 some years had a pipe plug back out of an engine case. It just does not happen.

Me either but they will seep oil. Seen that too many times. When that happens, you gotta clean the threads really clean, then the plug. Apply a tiny amount of 545 on the plug’s threads. Then twist it into place. Takes about 4 hours to set, but there is an accelerator you can use to reduce the time.

Thu May 08, 2025 8:28 pm

If you use the prep/activator spray it will harden in a minute. Since you are not using it on reactive metals like ferrous you have to use the activator or it wont dry. Most people don't even know the spray exists. You can also use it on 518 and 574.

Thu May 08, 2025 9:00 pm

I use 518 for loose/poorly fitting threads.
Normal red threadlocker will work better to get nicely fitting pipe plugs stuck.
You don't need an activator on brass

Fri May 09, 2025 7:32 am

Thanks everyone.

I've read so many posts with about 1,000 different opinions on what to use.

For fun, I called Henkel (Loctite) and ask about 518, and 545. They suggested both could work to some degree, 518 is less meant for threads and 545 is less meant for motor oil, but of course more depends on how good the threads are, but they went hard on Loctite 567, no activator needed, they say it has better oil and temp resistance even on magnesium and brass.

They also suggested that I need to decide which is more important - thread lockers will prevent loosening but aren't intended to seal at all, sealers will prevent leaks but aren't intended to prevent loosening. In their words, they don't have a product that will do both.

There is another thread on here where someone comments that anything with ptfe is a bad idea, (which is what Loctite 567 is) as it is a lubricant and will help plugs work their way out. Actually aligns a little with that Henkel said.

I guess at the end of the day, I just have to pick one! I do plan to stake these in, perhaps that with proper tightening is enough to worry less about backing out.

Fri May 09, 2025 7:47 am

I've got 565 in every pipe thread in my engines, no leaks. Continuous 300F intermittent to 375F. This is the 4th engine I have either personally put or seen get over 10k miles, never an issue. When I do break a fitting loose, it always has to come un-stuck from the locking compound, which is a low PSI shear but still a shear. This is not just gooey PTFE pipe dope, it has a locking element to it, just the "right amount." I've watched it seal when assembled in the presence of liquid hot dirty oil. I've watched it seal up a galled-up mismatched poorly machined threads on my buddy's hydraulic lift seeing 1500PSI. I'm a believer.

Fri May 09, 2025 8:09 am

Thanks Jimmy.

I did ask about 565, they had great things to say about it in this specific application also, but pushed that 567 is better for temperature and oil. According to them, its like 565 heavy duty.

Looking at the specs on both, they are both rated at low grip, could not find any breakaway data on brass for the 565 where it did have brass ratings on 567. Since I'm running brass plugs, I'll give the 567 a try.

In reading everything I can though, it does seem that careful tapping and prep and clean parts = 90%+ of what success looks like (makes sense).

Fri May 09, 2025 8:35 am

I used Indian Head Shellac for mine. No leaks or weeps and no backing out.

Fri May 09, 2025 9:37 am

I use 565 on all threaded fittings. No problemo

Fri May 09, 2025 12:15 pm

Over the past 15 years I've used 518 as a threadlocker and 640 as a sealant (backwards) probably thousands of times, with......believe it or not, near 100% success.

Which to use depends on the size of gaps you have.
A pipe plug should fit tight, so 518 is wrong, but if you have a loose fit, like say the pipe that your oil filter threads onto is wobbly in its housing, then that would be a good job for 518

Aluminum, stainless, or zinc plating needs to be wire brushed or freshly machined, steel and brass do not require it, but it still helps a lot.

Fri May 09, 2025 12:22 pm

Any of these will work.

I do not depend on threadlocker to keep the galley plugs in. Make them a tight fit. Then I file a notch at the top outer end and stake them in once they are seated.
To date....I have found that a good high temp, oil resistant, stiff durometer RTV (like permatex ultra gray) applied to the threads as you turn them in.... after cleaninguntil oil free with acetone or similar...works perfectly. Never leaks.

Ray

Sat May 10, 2025 1:08 am

Threaded plugs are so much work.
Dill, ream, tap, Clean, oil, test fit, tap, clean, oil, test fit, use a shortened tap, buy more taps, who stole the tap handle? tap handle hits studs, buy tap driver sockets, wear out your arms, use an impact wrench very gently, now your smart, then accidentally launch the thing into orbit with the impact wrench due to loud noise. Buy a flex arm machine, buy a larger building to house new machine.
Then clean the whole case and actually put it together with sealant.

I really like cup plugs more and more.
Pound it in with anywhere between .005 and .015 press fit with loctite, and it works, but it gives you the willies, just trusting that, but you just have to believe it, and do it right, and it's so much less work. Works for cummins and cat and chevy......and modern vws. the cup plugs on a...golf or passat engine are so wimply and thin i won't even touch them, i don't even think they would work, yet they do. Cup plugs can come in brass, and they cost very little. And can be done wrong too. Pocket has to be nicely chamfered and the driver does need to fit right, and sometimes quality of cup plugs varies, tho they cost so little you can't complain, but one in the hand is worth ten in the backorder.
Aluminum or magnesium has creep behavior, so no matter if it's threaded or not, everything will get loose eventually, replacing the plugs every decade or two is the only way to assure they are tight.

Sat May 10, 2025 6:28 am

Been using loctite 592 with no issues
https://next.henkel-adhesives.com/us/en/products/i...53459.html
Thick, anaerobic, sets slowly so you can adjust fittings if needed, doesn't hard set so future disassembly isn't painful...
It doesn't work for "loose" fitting threads, for that I'll use red loctite knowing someday disassembly may be awful.
I use the 592 for head studs too, works great.

Sat May 10, 2025 7:39 am

modok wrote: Threaded plugs are so much work.
Dill, ream, tap, Clean, oil, test fit, tap, clean, oil, test fit, use a shortened tap, buy more taps, who stole the tap handle? tap handle hits studs, buy tap driver sockets, wear out your arms, use an impact wrench very gently, now your smart, then accidentally launch the thing into orbit with the impact wrench due to loud noise. Buy a flex arm machine, buy a larger building to house new machine.
Then clean the whole case and actually put it together with sealant.

I really like cup plugs more and more.
Pound it in with anywhere between .005 and .015 press fit with loctite, and it works, but it gives you the willies, just trusting that, but you just have to believe it, and do it right, and it's so much less work. Works for cummins and cat and chevy......and modern vws. the cup plugs on a...golf or passat engine are so wimply and thin i won't even touch them, i don't even think they would work, yet they do. Cup plugs can come in brass, and they cost very little. And can be done wrong too. Pocket has to be nicely chamfered and the driver does need to fit right, and sometimes quality of cup plugs varies, tho they cost so little you can't complain, but one in the hand is worth ten in the backorder.
Aluminum or magnesium has creep behavior, so no matter if it's threaded or not, everything will get loose eventually, replacing the plugs every decade or two is the only way to assure they are tight.

Your comment pretty much lays out the total spread of the galley plug issue. It's also what I am always ranting about when the subject comes up again and again.

Threads on studs and bolts are one thing. They are not "plumbing".

With galley plugs we are essentially creating a plumbing component from a short ugly bolt. The threads have to SEAL against pressure.....not just tight enough to allow the vast majority of threadlocker to operate like you would on a blind hole or through hole for studs or bolts.

We see a bit of the same issue on cylinder studs and leakage....but those don't hold pressurized oil like an oil galley.

So, yeah a tapered plug has the finicky "grind the tap" and get the angle vs length correct. The best threads I can make for galley plugs are when it's a straight on hole and I can mount a case half on the drill press and use the Chuck and hand turn it to make CLEAN non-chattered threads. I think there are only maybe one or two I can easily do that with on a type 4 case.

The cup plugs. Do you mean steel cup plugs?

The original equipment style aluminum plugs....in the minds eye seem to be the easiest....seem to be. It's been many decades since I used to be able to get them at a dealer.

I round out real fast that the aluminum around each factory made galley plug hole spent decades expanding and contracting and is now fatigued. Just popping in the exact same size factory aluminum plug was a disaster in the making. You need to stake it in and it may still seep a little.

The steel cup shaped plugs (I have always called them freeze plugs) have some spring to them.
They still need a clean hole. I have never been able to find all the right sizes when I needed them for a Type 4 engine. I just do not build enough engines or I would probably find them and buy boxes.

Ray

Sat May 10, 2025 6:10 pm

I just pulled some gallery / galley plugs out that were leaking. The steel ones were the ones leaking. I am guessing that the steel had some oil that soaked into the pores during heat treatment when made, and that oil interfered with the Loctite 577 properly curing. We will know when this engine is run. Brass is not a bad solution but its expansion rate is about half that of aluminum. That is why I chose the aluminum plugs this time.

Sat May 10, 2025 6:28 pm

Presence of some oil residue on the parts did not interfere with curing in one of henkels own tests.
red threadlocker cured strongest on black oxide bolts straight from the manufacturer, without cleaning them.
Cleaning the black oxide bolts reduced the cure time and strength slightly, similar to the results of plain steel.

That kinda doesen't make any sense.......but, I think what it means is NOT that the oil was helping it cure better, but rather cleaning the bolts also removed some of the iron dust or grit which was helping it cure fast, and/or removing the oil and exposing them to water oxidized the steel slightly. The test did not say how they were cleaned, maybe that was a factor, maybe not.

Which.........while we don't know exactly why, is the same thing I find. To prep parts, I don't clean the male part, I wire brush the male part, or sometimes both parts. Some residue of oil may remain, but it doesn't matter, what matters is breaking the oxide layer and exposing/leaving streaks of fresh metal on the surfaces which the loctite will grab to and cure.

I think before your stainless pipe plugs..... were too clean, too smooth the with ill fitting rolled threads.

And I think if I had wire brushed the plugs before assembling then it would have worked fine.

the problem I have with aluminum plugs, threaded or not, besides being likely to gall, is the same problem with aluminum wire. It's not springy and it creeps loose.

But they do solve the difference of expansion problem, which is good.

Which is why I said if using aluminum plugs to wire brush them, and use a threadlocker, and install just snug. This way the acrilic plastic is doing the sealing and there is minimal interference fit, so it won't get loose over time, as there is no stress/preload on it to be lost over time.

Sat May 10, 2025 7:40 pm

Sorry to get too perfectionist about it.
It doesn't have to be perfect to work, but if I'm not working towards perfection then I'm not sure if I could keep working.

Sat May 10, 2025 7:56 pm

modok wrote: Sorry to get too perfectionist about it.
It doesn't have to be perfect to work, but if I'm not working towards perfection then I'm not sure if I could keep working.
I did not see your post until they were all in. In Henkle's spec sheet, they say anodized aluminum is Ok so we shall hope for the best. These plugs are in for the most part either the number of turns from finger tight, or torque, or both. One 3/8 plug I did not dare take to 21 because it was going in too far. It got up to 15 ft lbs. I put loctite 577 on the threads, screwed it half way in, took it part out, etc., or pulled it out and put more on the male threads until I could see that the male threads had pushed a good amount of 577 into thread roots most of the distance. I did use the primer. Kept compressed air in the gallery / galley the whole time so that any chips flew out at me instead of ending up inside. Just chased the threads with the new tap. It made a better thread than the original tap, which was also from McMaster-Carr. I can only hope for the best now. A little drip is acceptable, a puddle is not. :) I plan to put Yamabond over the plugs and aluminum to help slow down any leaks.

This thread was about using Loctite 518 on brass plugs. I use 518 on the type IV oil pump, and it has sealed well in the past, but it might be a little too thick for the threads on a plug for my thinking. Typically the threads get wiped as they thread in. The spec sheet for 518 does not list that high a pressure as a seal, and in direct contact with oil it loses part of its strength over time. Probably would last the life of an engine though because they give 1000 - 5000 hour strength change.