MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Oil Filter Magnet

Hello all.

I have been told that the ‘thing to do’ is to is to get a strong magnet and tape it to the top of my cartridge type oil filter. Thus any nasty bits of metal will get stuck to the magnet on the inside of the filter and my engine will last longer.

Is there any point in doing this as the filter is supposed to filter out these metal nasties anyway?

Will the magnet affect the way the filter works, or could it actually do more harm than good?

Would you do this to your beloved car?

Thanks!
Carwyn

Carwyn:
There are even rubber straps which have magnets spaced around them which go around the body of a filter. JC Whitney (USA) sells these and you may be able to find such a thing at Halford's. Or you can simply use a strong magnet that won't fall off as you mention.

The big thing is to remember to remove the magnet ONLY AFTER you remove the old filter. You don't want the metal chips dumped back into the oil before you remove the filter.
Bob Muenchausen

Carwyn,

Try obtaining a Unipart Premium oil filter

Paul
Paul

Carwyn-
People have been puting magnets on their oil filters with big rubber bands for as long as anybody can remember. It's a clever Ol'-Timey Mechanic's trick. It won't effect the way that the filter functions and can't do anything but good so long as you leave it/them in place until after you remove the oil filter cartridge. Moss Motors sells a magnetic plug for the oil sump which does the same thing.
Steve S.

the amount of steel (magnetic material) that gets into the oil stream should be very little. It is heavy and sinks to the bottom of the oil pan. I rebuilt a Chevy 350 v8 with an awful lot of miles. The cam was virtually round on some lobes. Some of the hydraulic lifters were worn all the way through. Lots of steel had been deposited in that engine. There was a fair amount of gunk in the engine but not really gummed up. I put it back together with standard size bearings and rings. It ran great for 50,000 additional miles as an RV tow vehicle. I sold it in good running condition. I've seen other engines with round cams and good bearings. My '97 Sonoma pickup has a magnet on the oil plug. For the first 30k miles I typically got a fair amount of metal shavings on the plug at each oil change (apparently left over machining material). Since then (now past 105,000 miles) nothing shows up.
Moral of the story: I'm not sure how much steel actually gets picked up by the oil pump and caught by the filter. Steel is heavy and settles to the bottom of the pan. If I was going to put a magnet anywhere it would be inside the oil pan or on the end of the oil pan plug. If there were a meaningful amount of steel that reaches the oil filter I'm sure we would have 8 different companies advertising their filter includes magnet protection.
Barry
Barry Parkinson

I'm with Barry

Put in a magnetic sump plug, at least it will hold the ferrous bits and stop them from going through the oil pump.

You can also check to see how much is has been picked up at each oil change, you may get some indication that something is amiss.

Cheers
ian f
Ian Fraser

I might be missing something here, but if there are metal particles in suspension in your oil, they're going to get trapped by the filter anyway. Most filters have a steel housing, and any kid who played with magnets will probably tell you that the magnet didn't work through steel very well at all. If I were to put a magnet in my engine...I'd opt for the magnetic drain plug. It the only logical place.
R. L Carleen

Just for what it's worth, when I change my oil this week, I'll use one of the magnetic drain plugs from Moss. They are available at Advance Auto etc., as well.

Dean
Dean Lake

A view on magnetic drain plugs, and magnets attached to the oil filter, are that they do not have the force needed to hold particle in oil flow, any debris captured by these products collect after the engine stops. When the engine is re-started, these particles break loose, and circulate in the engine causing damage.


Paul
Paul

but eventually, the mag drain plug will be removed and the metal accumulated on it will be cleaned off...no longer in the engine. These are bits too big to flow with the oil...or they'd end up in the filter.
R. L Carleen

cannot do any harm...more importantly use a magnetic draion plug on the gearbox....there are more metal shavings there to be concerned with and no filtering mechanism other than changing the oil regularly...
P J KELLY

Paul -
While I agree that a magnet on the outside of the filter may not work, a magnetic sump plug is not subject to any great flow. Particles held would not wash away.

Cheers
ian f
Ian Fraser

Ian,

May be the usual sales hype

http://www.filtermag.com/FilterMAG_tech.htm

Paul
Paul

Hi all..

Interesting stuff...

If anyone needs high strength permanent magnets, try the ones from a scrap computer hard drive.

HTH.. Don
Don

Thanks All!

Looks like I'll be replacing the sump plug with a magnetic one then...
Carwyn

Another good source of heavy duty magnets are the magnetic disk erasers that IBM 'used' to make (maybe they still do??) Those were some vicious magnets!

I have used both the drain plug magnets and a stout magnet on the filter can and both have collected debris. Considering how small the particles of metal are that get into the oil flow, I don't think that weight has much to do with how they circulate, only where they fall out when the oil is not circulating. Therefore, a sump plug magnet is probably good over time, but one in the filter, a "slow down point" in the circulation, seems to grab some of the metal particles too. FWIW
Bob Muenchausen

Bob-
So true. I've been using both methods for over thirty years and am always surprised at what gets caught by the magnets. Of couse, the magnets are no substitute for a good, fine-straining filter!
Steve S.

The magnet is not a trick nor is it some sort of cheap way of filtering oil...they do work for their intended purpose which has been touched upon by several in this thread.

The magnet on the oil filter is probably useless.

The magnet in the sump is a good idea and cheap.

Porsche thought this was a sound application for twenty years of production.

The 356/912s all have magnets in the bottom of the sump right around the pickup tube.

erik.
Erik

Hi,

First off... If you have metal bits in the sump your engine is trashed anyway. 2nd.. The metal, if any is probably babbit - the coating that is covering the copper in the bearing..It usually settles over a long period of time in the bottom of the sump as a fine silt like stuff. When you take the pan off that grey stuff that you see at the bottom of the pan is babbit. Most sump plugs are magnetic and I have NEVER seen chunks of metal adhering to the plug at oil change time. If you crack a ring it will most likely stay in the piston groove trapped between the piston land and the cylinder wall. If a lifter breaks or collapses (sp?) you will know it and no magnet in the world is going to save that engine especially if it is running hard when a lifter or cam or timing chain cashes in. If a piece of piston skirt breaks off, you will know it by the thrashing sound as the engine destroys itself there are tremendous piston speeds and pressures involved inside that engine. There are no chips of metal in any well (tight) running engine floating around waiting to get caught in a filter or by a magnet. Cut open a few used oil filters yourself to see what has been caught in the filter. Just small pieces of dirt that have been ingested by the intake. No chunks or splinters or shards.The filter material is measured in microns. Alan
Alan

Alan
You are probably right with regard to the type of failures that you mention.

However cam followers and cams do progessivly wear, and occasionally the hardening on the follower will come off as a small flake. This sort of wear is not always noticable by way of engine noise or performance loss. ( rocker shaft wear is another)

I have always had magnetic sump plugs, and occasionally I have found a flake on the magnet. Its not a biggy putting in a magnetic plug, and if it catches any flakes that would otherwise go through the oil pump, and provides a warning that something is amiss, it seems worthwile to me.
Cheers
Ian F



Ian Fraser

Ian

If the hardening is coming off to that degree, your engine is already dead. May run, but is past "worn out" and the positive thing is, at that stage, you do not have to change oil anymore - simply keep adding it because the engine will be burning as fast as you can pour it in. The oil pump is attached to the engine and the strainer is suspended below it (with a screen)but does not touch the bottom of the pan. Stuff like that will become lodged in the far corners of the oil galleries and further add to wear because the oil is not flowing to the bearings etc. as it should. Alan
Alan

Ian-
Most of the metal flakes that I've seen were leftovers from the machining operations that were performed on the block. Although the block is invariably cleaned out after all of the machining operations are done, sometimes this is not done as diligently as one would hope. In any case, there's always a little bit left lurking in the recesses that are the most difficult to clean, just waiting to do harm at some future date. I've seen these flakes appear in the oil of engines that had over 50,000 miles on them. A fine-straining filter may stop them, but such a filter gets clogged up earlier and then then its bypass valve opens, allowing everything to circulate with the oil, be it dirt, grit, metal particles, bits of old dinosaur bones, you name it.
Steve S.

The kind of stuff I have found on the magnets used in any car I have used magnets on is obviously ferrous material, and in almost all cases, from low mileage Audis to high mileage MGs, it has been an extremely fine dark grey powder. There have not been nearly so many flakes, if any, and usually, not very much debris at all, either inside of a filter (I have taken apart a couple of filters to see if there really was anything trapped or not, and believe me, it was not a lot, but enough to say there was some)or bristling off of the little anemic plug magnets in the sump.

Given the nature of what I have seen, I assumed it was probably the inevitable grist from cast iron rings running on cast iron blocks, good oil or not. When cleaning out sumps, usually I have found a gummy puddle of ashen colored muck about the size of a nickel at the lowest point, and I have been told that this stuff is indeed ash of a sort from combustion. What the truth is, I don't know, but it is not too hard to see that it is generally not flakey, just tiny. Where I have seen flakes (and these too are small, 1/64" or less) much more often is in the bottoms of trannies, and/or usually only in blown up or brutally thrashed engines with flattened cams or galled steel parts. I think Steve S. has more experience than I do rebuilding engines, tho, so I would think he should know what we are seeing. FWIW
Bob Muenchausen

Bob-
That ashen-colored muck is indeed the byproduct of combustion. Carbon molecules from the seared oil on the cylinder walls bonded to ash. The super-fine gritty ferrous dust? Usually iron dust that clung to the porous cast iron walls of the block left over from the machining processes. Really teensy-tinsee silvery specks? The coating from the plain bearings. Enlongated tiny flakes? Probably chips from the edges of the rings. Hey! Change your oil more often and stop using those #@$&^*%! cheap filters!
Steve S.

Castrol GTX 20w-50 from day one, Steve. The stuff I have collected over the last 25 years from several different cars and trucks would not have filled even half a small thimble.

To me, using magnets is not nearly as worthwhile as frequent changes of oil AND filters. If a person really wants to know what is happening in their engine, they can order an oil analysis kit and testing from an industrial equipment service corp like Caterpillar which will tell them much more, and more scientifically probably, than they might really want to know about what is going on inside their engine.
Bob Muenchausen

Very interesting thread. Many view points, all of which are valid. I will, however, agree that the best way to monitor your engine is with frequent oil changes and a magnetic drain plug. I use a magnetic drain plug in all my engines regardless of age. It is a quick way to tell if you are about to experience a catastrophic failure. And yes, I have caught failures before they happened this way.

As an aside, I am presently restoring a 1952 Pontiac Chieftain four door sedan for the wife to drive around town in (talk about extremes! From a 73B (MINE!) to a 5000 lb behemouth!). The old straight eight does not even have a filter. It has a type of cleaner/ sediment filter inside the oil pan (it's BIG too). The shop manual explains that it is sized for the life of the engine. It also states that the cleaner needs to be serviced if the car has been rolled over. I am not sure why that passage is in there. Did people roll these monsters over very often!? I know from research that straight eights were almost impossible to kill. They way outlived the cars they were in and were used in sawmills and the like for years and years after their cars died.

Anyway, I completely rebuilt the old girl and when servicing the cleaner I found nothing more than the usual sludge, gray matter(babbit), and a few small particles. Not bad for 53 years. However, after running the new engine for a few hours with a magnetic drain plug, I got a few small shavings out. I am (almost)sure that it is leftover machining crud. But I will keep a close watch for the next few runs(I just pull the plug and hold my finger over the drain hole while looking at the magnet)to insure that something is not going wrong.

Bottom line is: Magnetic drain plugs rule if read correctly.

.02 worth,
Mark

73B "little purple car"
52 Pontiac Cieftain "Gertrude"
http://emtee.wirefire.com
Mark Thomas

Bob-
That wasn't aimed at you in particular. I completely agree that there's no substitute for frequent oil changes and high quality filters. I use Mobil 1 in the engine with K&N oil filters and Castrol 20W/50 in the transmission. Why don't I use the less expensive Castrol in my engine? Simple: most of the wear that takes place in an engine occurs during the warm-up period because the oil is too thick to flow easily. Once the engine gets up to operating temperature, it flows freely and does its job well. The Mobil 1 synthetic flows just as well cold as it does when it's hot. It also doesn't thin out at high temperatures, which is a serious plus in an engine that's been modified for higher power output. Why don't I use it in my transmission? Because the transmission seems to shift a bit better with the Castrol oil. Go figure! How often should you change your oil? Read on- All of your comments on acid buildup and condensation are right on the money. However, there's another factor that needs to be mentioned: the effects of blow-by. Just because a wet compression test may give readings that seem up to par doesn't automatically mean that the compression rings are doing an adequate job of containing the enormous pressures of combustion. When partially burned fuel blasts past the rings and onward into the crankcase, the oil becomes contaminated with carbon, one of the hardest substances known to man and the enemy of all precision-machined surfaces. It's the stuff of which a blueprinted engine's nightmares are made of. How to tell the condition of the compression rings without putting the car on a dynometer and running it against a heavy load? Simple: If your oil turns an opaque black within 3,000 miles, you've got a problem. How to protect that big investment that you've made in your newly rebuilt honey? First, be picky when it comes to your choice of oil. Use only the best. True, you can use lesser quality oil and never experience an oil-related failure. Today's oils are far better than what was available thirty years ago, and outright failures that are oil-related are all but unknown today. Nevertheless, a better oil can mean a longer engine life. Second, always change the oil filter whenever you change the oil, and use the best oil filter that you can get. The fewer solid particles there are circulating inside your engine, the better. The top oil filters right now are the Mann (Part# W917), Purolator Pure One (Part# 10017), Motorcraft (Part# FL300), AC Delco (Part# PF13C), but the most effective is also the easiest to install: the K&N Performance Gold Oil Filter (K&N Part # HP2004). Third, be ruthless when it comes to oil changes. If the oil is opaque, change it. If it has 3,000 miles on it, change it. If it's been in the engine for six months, change it. If you're putting the car in storage for the winter, change it. When you change the oil, don't be hasty and replace the drain plug when the drain flow slows to a drip. If you put a measuring cup under the drip and wait a couple of hours, you'll get about twelve additional ounces of the nastiest, grittiest stuff you'll ever have the displeasure to see coming out of an engine. This cr@p will wear out your engine. Get all of that old oil out. True, you don't have to be as fanatical as I am. You can use ordinary oil, ordinary filters, change your oil as quickly as you can, and still expect to get a good 80,000 miles out of your engine. Today's oils really are that good. But personally, I figure that if I don't get at least 140,000 miles out of an engine, then it's a lemon. To me, 180,000 miles is more reasonable.
Steve S.

Hi all...

In the interests of science, I just performed an experiment.

I took an old disk drive magnet, (cost = 0) a tin-plated steel biscuit tin and some steel woodscrews.

The magnet was applied to the outside of the tin, and the screws placed inside.

The screws stuck fast to the tin at a point above the magnet.

I have to go now.. I have to do some magnet installation.....

Don

PS... If you do apply magnets to your oil filter, I suggest you leave them on until the filter is off the car when you change it.

Don

Steve, I didn't take it that way, I just thought you should know what I was using, since I know you use Mobil 1. I expect that there will be some friction related grundge in the filter and pan from cold starts, but it never seems to amount to much, even at the magnetic drain plug.

To speed up the warmup period, I use Neil Cotty's little trick of using an ordinary T-stat combined with a bypass sleeve. The engine warms very quickly, yet the sleeve does not seem to affect cooling efficiency even on the hottest days. With any luck, this helps the Castrol to come up to temp quicker than it normally might, but you are right about the properties of synthetics. I think this is one place I am probably pennywise and pound foolish. ;-)
Bob Muenchausen

A link to oil filter tests

http://www.scuderiaciriani.com/rx7/oil_filter_study/

Paul
Paul

This thread was discussed between 02/10/2003 and 05/10/2003

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.