Mystery object in oil change pan.... ideas?

[shantillylais]

Car is '92 4.2 diesel, 261000km. Aftermarket DTS turbo, aftermarket oil cooler from the front oil filter position, shell rimula X oil has been changed every 5000km as required, and is at worst very light grey. After draining my sump and changing the filters (Z115), when I was emptying the oil into my used oil drum, I noticed a mystery piece of metal (steel) in the bottom of the drain pan. The object is about half inch or 12mm in diameter, about 2mm thick (one sixteenth inch), has the stamp mark 1/2 in the centre. From marks on the edges, it has obviously been pressed from a sheet, sort of like a welsh plug but very much smaller. My engine works perfectly, 60psi oil pressure (4 on the standard gauge), normal coolant temp, no strange noises. We have searched the workshop manual end to end with no indication of such an item. To the best of my knowledge, it didnt fall from somewhere else, and was not in the pan before the oil. I have had suggestions like a balance weight from the crankshaft manufacture, a stray balance weight lost when the engine was manufactured that wasnt found before sump was put on, perhaps a oil galley plug (but unlikely given my oil pressure and general well being of the engine). It has everyone I know stumped. Over to you experts please.

[HiFiRobbie]

I definitely sounds like a welsh plug. The "1/2" stamping is the diameter, this gets stamped into most welsh plugs when they are manufactured.

Where it's from? I dunno. But if everything is still running fine, don't worry about it.

You have strong oil pressure and no water leaks so forget about it!

[Andrew44]

perhaps it has been lodged somewhere on the outside of the engine on in the chassis somewhere. It may have fallen down and into the tray as you were changing filters etc.

[geordie4x4]

Is half inch too big to have come out through the sump plug? Test that and you will know if it did not come out of the oil or if it may have.

[Twinotter600]

If you get worried enough, have your oil filters cut open and inspected.

[shantillylais]

did the above for curiousity. wondered how the antidrainback valve worked. no metal inside other than the screen. Have to get another sump plug to try the size bit, that had been suggested but our parts shop didnt have a listing. We wondered about the 1/2, thinking it meant "half", but was suggested it may be "1to2 mm" or 1 to 2 grams (as in balance weights). It seemed strange that a japanese engine would have imperial numbers stamped that is referring to the half inch. None of the outer welsh plugs have anything stamped on them.
BTW, no wonder anti drain back valves stop working, wouldnt take long to harden a rubber flat ring covering the ring of small holes from the inside, which is all that the anti drainback valve is in Valvoline filters. That was my one and only venture away from Ryco z115's.
Keep the ideas coming .... all welcome.

[mav-i]

Sounds like a friday arvo job to me

[jerbGQ]

Is it magnetic?

[4bboy]

pushing in old welsh pulgs is one of the ****ist things mechanics do

it takes fark all more time to pull them out

my 2 cents...........................

[HiFiRobbie]

I had a little bit of a brain wave today when I was reading this one again...

What you have described sounds similar to the little plugs that are used to plug a crankshaft counterweight after it's had a little bit of Mallory Metal put in it for balancing.

Not being all-knowing about Nissan Diesels, I couldn't say for sure, but it may be worth checking with a specialist to see if the crankshafts are balanced internally or not.

Basically what happens is the counterweight gets bored into from the side and a little slug of metal is placed inside that is heavier that the steel or iron that the crankshaft is made out of. This way they can actually add mass to the crank rather than drill the guts out of it on an opposite journal. But, this is normally something that only gets done on race engines as it ain't cheap!

http://i198.photobucket.com/albums/aa83/hifirobbie/balancing.jpg

Just another thought...

[shantillylais]

hello Robbie, I showed that reply to the guy who suggested the balance weight idea, and he agrees. He was a Nissan mechanic and trainer but prior to the GQ, so was apprehensive to be totally positive. 4bby, it isnt an external welsh plug for any mechanic to "push in" and its really small, when measured, its not exactly round, being between 12mm and 12.5mm, its far to clean and non corrroded for a water area, or even plain "weathering" from age. What ever it is, it hasnt affected anything so it must have been there for quite some time, most likely from manufacture, because I have just travelled over 500km and some of that with my 'van on the back with no changes to water or oil performance. So I guess it remains just one of those mysteries.

[pigsy]

Just changed all my welsh plugs on my TB42 and it is to my beleif that both blocks , petrol and diesel are the same .
Down the left hand side of the block below the manifold is a row of six baby welsh plugs 18mm part of the water jacket they get full of crap behind and push out could be what you have found good luck