Author Topic: oil sump intake screen blockage  (Read 26 times)

Hugh Conway

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oil sump intake screen blockage
« on: July 17, 2019, 08:54:18 PM »
I was changing oil at 1850 hours a few days ago, and removed the sump oil intake screen to clean it.
I had only removed it once before on the initial cleaning/reassembly.

On inspection, there appeared to be something  INSIDE the screen that would not wash out.
The foreign object could move from one end of the screen to the other and was nearly the ID of the screen.
When shaken, it moved from mid-screen to the threaded end, made of steel (not brass) in this listeroid. I had to use a rod to dislodge it from the threaded end, pushing it back into the screen.
The object was larger in diameter than the threaded end, so could not be removed. Whatever it was, how did it get in there?

I cut the end off the screen to get this thing out and discovered it was a magnet, cylindrical and with tapered rounded ends and shaped like a large very smooth rat turd. I suppose it seemed like a good idea to the manufacturers, but it could very easily migrate to the threaded end of the screen assy and effectively shut off oil flow. Sure glad it did not! With the magnet/oil shut off valve removed, I re-closed and re-installed the intake screen thinking I had dodged a very large bullet!

I had early on put a couple of magnets in the sump, so this OEM one now sits on my shop window sill as a reminder that with a listeroid, ANYTHING is possible!
JKson 6/1  (Utterpower PMG ) Off-grid
Lister 6/1 Start-O-Matic engine......running with PMG
1978 Royal Enfield (glutton for punishment by Indian iron)
1963 BMW R-27 project


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Re: oil sump intake screen blockage
« Reply #1 on: July 17, 2019, 11:53:37 PM »

I find magnets in engines to be of little value.
Most engines have little Ferrous material in them to start with, mainly rings and bore.  The particles that come off them is very, VERY fine and anything under about 7 UM according to tests I have read don't matter because they will fit between clearances with room to spare anyway.

If an engine has a couple of thou wear, it's pretty much buggered and needs a rebore , new bearings etc.  That amount of wear would normally occur over 10's of oil changes so the amount of material that could be in each oil change would be minimal. Many engines have filters or ways of catching the particles and holding them for later removal.

Magnets don't catch material from bearing surfaces which a lot of particles will come from as it  is non ferrous.
Up till now I would have said a magnet probably can't hurt if it does not help, but that's been shown here to be wrong. Is there anything on a good original design on these engines the Indians can't Fu... Bugger up?

In gearboxes and Diffs, I have seen where magnets can pull a lot of material from these components, especially when they are new.  I have also see magnetic sump plugs from modern car engines which reaffirms my not worth the trouble position on them.

Bit like when people in the veg Game used to obsessively Centrifuge their oil/ Fuel to sub micron levels though when pump diesel is only Filtered to 10 UM and that's only what most OEM fuel filters were rated to anyway because anything smaller would pass right through pumps and injectors without problem.

Magnet in the pickup probably seemed like a good idea or was responding to a customer request but the possible side effects were not thought through  very well.

I remember back in the early '90s the best selling car here at the time had a GM V6 3.8 L engine fitted.  They had a small pickup  screen about the size of half a Golf  ball.  The screens were notorious for blocking and starving the engines for oil.  First it was thought to be lack of regular oil changed but that turned out not to frequently be the case.
People( Not naming my wife) would see the oil light come on and of course as is human Nature, just want to drive the thing home. She...... errr, THEY, of course never made it.
They eventually went back to the wide, flatter pickup design pickup with a screen area about the size of a large tea cup rim.