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MG TD TF 1500 - Rare Earth Neodymium Drain Plug Shocker

I embedded a neodymium magnet in the drain plug for my sump.

When I pulled it today to do an over due oil change a plug of gunk came with it. After wiping this off I was left with this collection of swarf still sticking to the magnet.

The good news is the magnet really worked.
Bad news this looks like a lot of engine I would rather have left where is should have been.

You can see some of the thick black gunk in the background on the paper towel.

This was the first oil change since the head was skimmed.

I am changing the filter, running the car for a short while on 20/50 oil specified for diesel and petrol cars ( high detergent) changing again to the normal valavoline I use.


D Moore

It's more than I like to see, but not uncommon. I wouldn't worry about it.
Steve Simmons

Not sure what "high detergent" means as there are no cleaning agents in any oil made in the last 30 years. As you may know "detergent" oils only keep stuff in suspension a bit longer than minder regent oils so they can be trapped in the filter . Regards, tom
tm peterson

Non oil filter engines like Model A and T Fords, small lawn mowers, etc., use non-detergent oils so the trash sinks to the bottom and stays there.

Engines with filters should use oils with detergents and dispersants so the filter can capture the crud, so it can be tossed with the filter.

Metal shavings will sink no mater what kind of oil you use.

I'd be pretty eager to drop the pan and look at a few bearings if I pulled a magnet out of my engine that looked like that.



I bought a magnetic sump plug from Mad Metrics when I rebuilt my engine in 2006.

I was appalled to see what came out on it, on the first oil change ... just like David Moore's.

A small investment with good returns!

Gord Clark
Rockburn, Qué.
Gord Clark

Do the neodymium magnets attract all types of metal or just iron. Surely a conventional magnet will not pick out bearing materials. I would argue the only sources of the material stuck to the drain plug would be swarf from the machining processes or bedding in wear from the bores/rings. Aren't magnetic plugs of far more use in the gearbox.


Jan T
J Targosz

The dual use petrol/diesel engine oils have higher than normal detergents/ disspersants.

This is because they have to cope with the higher level of 'crud' created by diesel engines.

As MAndrus notes above they keep the crud in suspension to take it to the filter or have it removed when the oil is changed.

The magnets just attract iron - they are just a hell of a lot stronger than normal ones and can stand the heat.


D Moore

Hi Dave,

A magnetic sump plug will pick up ferrous metal. It won't pick up bearing metal. They will always come out covered in a soft, fine metallic sludge. I would guess there would be more sludge first time after fitting a magnet.

My concern is that, from your photo, the "metallic sludge" appears to have sharp shards in it. If that is the case I would think that one likely source is the cam followers. At least they are fairly easy to check. Maybe also rinse the sludge in solvent to see what the bits look like.

Bob Schapel
R L Schapel

Those sharp edges are almost certainly not single pieces of metal. Typically it's just an effect of the magnetism. If you roll the swarf around in your fingers, you should see it's actually just powder.
Steve Simmons

Steve is right. It is just the way the grains lined up when I wiped off the sludge. No sharp pieces :-)

D Moore

This thread was discussed between 04/09/2015 and 08/09/2015

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