How are magnetic drain plugs made?

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I want to experiment with modifying a magnetic drain plug. One thing I am not certain of is how they keep the magnet in the center of the drain plug and how the drain plug is made "around" the magnet?

I've tried pulling on the magnet and it doesn't come off. There's a little rotational play but that's about it. Does anyone know how they make these things and keep them together? Is the magnet threaded and do they thread it into the center or something? I suspected this and did a little searching and found this:
Magazi-anodized-black-aluminum-magnetic-oil-drain-bolt-plug-M12-P1.5-bike-KTM-honda-06.jpg

But I suspect that's not applicable to Honda ones for example since I see nothing in the square drive hole or any kind of pin they drove it from the circumference to keep the threaded portion from backing out.

Here's the kind I'm wondering about:
blogger-image-1129378425.jpg
 
Never seen the type drilled through like your photo. Looks like a passage for "leak through" failure to me.

In a steel plug wouldn't the magnet hold itself in place?...with a little industrial adhesive for security.
 
Oh wow really that's all? Just adhesive and magnetism?

I've hit the drain plugs up with brake cleaner from time to time, hope it didn't do anything to the adhesives ahahahaha.

The magnet should hold to the steel drain plug though that's right.
 
Originally Posted By: shanneba

A regular grade N neodymium looses magnetism at 79 Degrees C and often dumps all the swarf back into the oil!


I have proven this to be 100% untrue.
 
Originally Posted By: shanneba
http://www.magneticoildrainplugs.co.uk/Technical_information_Magnetic_Oil_Drain_Plugs.html

Each Dimple™ Drain plug will have the magnet secured using the finest 2 part resins available.
A regular grade N neodymium looses magnetism at 79 Degrees C and often dumps all the swarf back into the oil!




Yeah this is a lie, what happens is a low temp magnet (ie 175F working temp) loses some strength WHILE AT 200F
and recovers when it cools. The amount lost is about 20-30% by my observation. TOTAL loss occurs when you hit the CURIE POINT
which is much higher, around 350-400F

It's notable that GM uses cheap ceramic ring magnets in trannies near 200F, you can bet they have a working temp of just 175F, but
at least do something.

Interestingly, if you order hi temp magnets, there is a trade-off, the higher the temp rating is, kiloguass rating drops a bit,
but stays steady at the rated temperature.

While some folks had picked up lots with a magnetic oil plug, the reality is, to make a real dent, you need a lot of magnets to see a
PPMs drop in your UOA, so the best place for that is at the spin-on oil filter, in my case: 2 FilterMags, 2 bar mags inside, 4 more bar
mags outside between the FilterMags and 1 mag on the end, gives me a 50% iron drop, but then I was at 15PPMs to start with, ie, not the
high. If you have really high iron numbers and big particles, you may see a bigger percent drop, but also you have a wear issue!
 
BTW, the fastest product way to mount the mag in the plug is "press fit" with a small press
and a calculated interference fit.

I fabricated one with an existing oil plug, drilled out, inserted a 2" long neodynium magnet and
press fit a small roll pin next to the mag with a small arbor press, figure about 100 Lb force.

Put it in my sunday driver. The 2" long mag has lots of surface area exposed to moving oil with
a better chance of catching wear metals. A small short mag is hardly worth it.
 
My 99 ford had a donut magnet in the pan. After 17 years when retrieved it had about 6 ounces of metal shaving. I cant imagine a portion of it wud get loose at hot temp. My tranny gets to about 205 f max.

It is one strong magnet though. Even if it lost 20 percent strength it will still be awesome. Wonder if i should have kept it in the pan and not rely on the new magnetic drain plug !
 
Last edited:
The purpose of magnetic drain plugs is not to remove all the Fe. It's to be an indicator of an issue at Oil Change. We do this with race motors all the time. If it has Fe "hair" on it, you have an internal problem. The better source is the filter mag if you want to drop Fe metals out of circulation ...
 
Originally Posted By: BrocLuno
The purpose of magnetic drain plugs is not to remove all the Fe. It's to be an indicator of an issue at Oil Change.


Which, at non-race OCI's, is quite likely to be TOO LATE.

A magnetic dipstick gives you continuous monitoring, so is likely to b a lot more useful diagnostically. Plus you can clean it.
 
To get all the existing metal out of atf

Could one on a cold engine install like the mother of all magnets to the pan right near the drain plug. Then run the car in driveway for about 10 minutes cycling through all the gears. This avoids bumps and shakes one would get on the road. Then drain the atf.
 
Last edited:
Originally Posted By: merconvvv
To get all the existing metal out of atf

Could one on a cold engine install like the mother of all magnets to the pan right near the drain plug. Then run the car in driveway for about 10 minutes cycling through all the gears. This avoids bumps and shakes one would get on the road. Then drain the atf.



I hear ya!

The reality is that a 10 minute run is no good, for a magnet to catch what it does requires oil to pass it thousands of times
or more to catch any one particle. That sounds bad, but w/o a magnet none of the iron would ever be caught at all. Any spin-on filter
is only 'good' at particles 20 microns (half a thou) or bigger. normal wear metals are 10 microns on the 'big side' down to .1 micron.
So a magnet is the only way to catch it.

My OCIs work out to 350 engine hours, that's the same oil going thru a spin-on oil filter with a pair of FilterMags 400,000 times or more! Ditto for AFT in the
tranny. Because of oil thickness, oil speed and small particle size, a huge number of passes are needed before any specific particle is
within 1/8" to be caught. But it works. My engine oil stays cleaner longer and UOA show a drop in all metals.

In my 4T65E tranny, lots of mags, even after a shift kit is helping steadily reduce the number PCS solenoid malfunction events w/o pulling
it all apart for a $40 solenoid!
 
I should mention in my post above the mother of all magnets would be attached on the outside of pan. Then the engine runs and turned off after a set time.
The magnet removed. Then drain.
 
Originally Posted By: merconvvv
I should mention in my post above the mother of all magnets would be attached on the outside of pan. Then the engine runs and turned off after a set time.
The magnet removed. Then drain.


This seems likely to be LESS effective than a straight drain with no magnet.
 
Originally Posted By: merconvvv
I should mention in my post above the mother of all magnets would be attached on the outside of pan. Then the engine runs and turned off after a set time.
The magnet removed. Then drain.



Yup, I know where you're coming from, but any magnets on the outside of the oil pan would have their fields shunted out by the thickness
of the steel, even just .040" to .100" thick, this means very little of the magnet's strength reaches the oil.
I tried on steel plates of various thicknesses, then gave up the idea and went for magnets (lots) all over the spin-on oil filter were
the shell of the oil filter is always thin, .010 to .020".

If have an aluminum pan, the field is stronger, but holding the magnet to the pan is a problem. Bummer eh?
 
Originally Posted By: i_hate_autofraud
Originally Posted By: merconvvv
I should mention in my post above the mother of all magnets would be attached on the outside of pan. Then the engine runs and turned off after a set time.
The magnet removed. Then drain.



Yup, I know where you're coming from, but any magnets on the outside of the oil pan would have their fields shunted out by the thickness
of the steel, even just .040" to .100" thick, this means very little of the magnet's strength reaches the oil.
I tried on steel plates of various thicknesses, then gave up the idea and went for magnets (lots) all over the spin-on oil filter were
the shell of the oil filter is always thin, .010 to .020".

If have an aluminum pan, the field is stronger, but holding the magnet to the pan is a problem. Bummer eh?


Just as well.

Magnets are here being suggested as a way to enhance the effect an oil change, which doesn't seem to make sense.

If you've got metal suspended in the oil, and you drain the oil, you get rid of the metal.

IF you succeed in pulling some of the metal to the bottom of the pan, and you drain the oil, you'll probably leave some of that metal behind.

IF there's any residual magnetisation of the oil pan or the metal, you'll leave more of it behind.

Magnets don't seem likely to help metal removal, but they could hurt it.
 
Originally Posted By: Ducked
Originally Posted By: i_hate_autofraud
Originally Posted By: merconvvv
I should mention in my post above the mother of all magnets would be attached on the outside of pan. Then the engine runs and turned off after a set time.
The magnet removed. Then drain.



Yup, I know where you're coming from, but any magnets on the outside of the oil pan would have their fields shunted out by the thickness
of the steel, even just .040" to .100" thick, this means very little of the magnet's strength reaches the oil.
I tried on steel plates of various thicknesses, then gave up the idea and went for magnets (lots) all over the spin-on oil filter were
the shell of the oil filter is always thin, .010 to .020".

If have an aluminum pan, the field is stronger, but holding the magnet to the pan is a problem. Bummer eh?


Just as well.

Magnets are here being suggested as a way to enhance the effect an oil change, which doesn't seem to make sense.

If you've got metal suspended in the oil, and you drain the oil, you get rid of the metal.

IF you succeed in pulling some of the metal to the bottom of the pan, and you drain the oil, you'll probably leave some of that metal behind.

IF there's any residual magnetisation of the oil pan or the metal, you'll leave more of it behind.

Magnets don't seem likely to help metal removal, but they could hurt it.




Ducked,

You raised good points of magnets in on on the outside of the engine oil pan or the outside of a tranny pan.

Pulling iron out of the oil as the car /truck is driven helps reduce wear those particles cause when otherwise left in the oil
for a 3K OCI or longer. So yes, they drain out in an oil change, but getting them out of the oil flow as initial wear occurs
is a plus if you want to keep an engine 300K and still pass smog tests, get good mpgs, good compression and ear new power.

My point I guess, is that metals left in the oil cause 'secondary' wear.

I wish I thought of using magnets in the 70s, up to 2012 when I ran big distances in Mopo 318 V8s that got really worn at 300K,
low comp and mpgs and just accepted it and the poor condition of the oil even at 3K OCIs!
 
That cut away drain plug doesn't appear to have much metal at the first thread root. That design wouldn't take the 33 ft. lbs. of torque I use on my drain plug. Snap right off at the first thread root. " But I had a torque wrench on it"
laugh.gif
 
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