Did you happen to see the orifice the wheel dropped in?
​​​​​​It's an orifice that is plugged (blocked off) by the oil filter's o-ringed snout, so oil doesn't travel thru that orifice to/from the oil filter. (post #24 shows)

​​​​https://mbworld.org/forums/glk-class-x204/817890-ack-dropped-caliper-thumb-wheel-into-oil-filter-housing.html#post8366570

But the screen would keep the wheel from getting to the pump. one idea suggested is to place earth magnets on the small steel pan cover in the area of the mouth of the pickup tube.
​​​​​​

 

I have 55 years experience building engines for everything from lawn mowers to aircraft. Either you don't understand what I'm saying, or you are disagreeing with me.

The hole where the cable tie is in post 99 is not open to the filter. It is completely closed off by the plastic bit that sticks in the bottom of the filter. When you loosen the filter that plastic bit pulls up out of the hole and opens that passage to allow the oil in the oil filter housing to drain back into the sump. see the photo in post 10. If that were not true then the filter housing would be full of oil when you remove the filter, and it would make a huge mess.

The outlet from the filter into the oil galleries is the level above that one, blue in post 1 (also in post 24).

Review post 24 which has photos of the three openings and correctly describes how they work other than that it is correct that oil from the pump enters the filter under pressure through the yellow opening.

And, yes, you are correct, it's called a windage tray.

OP, if you can get your hands on a speedometer cable core it is strong enough and flexible enough that you should be able to wind it all the way down until it exits into the crankcase somewhere. (Find an older car in a junk yard, or, speedometer core replacement kits used to be common in any parts store) Put a slight bend in the end, then rotate it as you feed it in to help it find its way around the bends. It's sort of a moot point since you've already confirmed that oil pumped into this hole comes out in the sump. None of the pressure feeds would do that, at least not while you watched. It takes about 10 psi to make the oil flow and you'd need a column of oil about 25 feet high to generate that much pressure.

[Edit] I see the OP has already clarified some of these points while I was composing my response. I'll have to be faster next time!

 

I just spent 30 minutes with the "magnet on a wire" pickup tool.
3-4 inches after the magnet enters the orifice, it's sticking to something magnetically. I worked the tool gently so I could feel the feedback - it is sticking to whatever ... and if I move the magnet very slowly in an upward motion feels like bolt threads. Could it be the knurls of the wheel and it's wedged? Probably forcing the thought

 

Maybe you can fashion a little hook to go to the same place, and dislodge it, if it's the wheel, and pull it back with the magnet.

Or, could it be a bolt? (Probably not; it's not likely there is a bolt passing through an oil drain passage.)

At this point, I think your options are these:

• Button it up and cross your fingers.
• Take the timing cover off.
• Sell it as is.

It would be nice if you could find someone who has that timing cover already off the engine, to look at. You could test drop your other wheel...

 

I'll do the hook fishing today
And yes, last night I spent an hour internet searching for photos of the front of engine with timing cover off / mating side of timing cover itself - nothing yet, so will keep looking

 

If that's indeed really true, then yes I would not worry about it because it ends up in the sump and the screen in the pick-up tube won't let is go anywhere.
I have my doubts that that hole serves no purposes during normal operation, but I don't know for sure. As you know, oil has to be able to bypass the filter at high pressure. I don't know for sure how it's done on M276. My assumption was that one of the center holes is for oil to by pass the filter.

 

Indeed, provided that piece ends up in the sump in the first place. Yes, this would be the best case scenario.

 

Finally found a clean crisp photo of the front of m276 engine without timing cover - wish they had photo of backside of timing cover ... it's a start, I guess ... found at Chinese Alibaba website

Literally spent countless hours to find this

 

True. When the differential pressure across the filter exceeds a safe value, the filter goes into bypass mode. With cartridge filters it's usually done by having the cartridge lift up off the bottom of the housing so oil can flow directly from the inlet to the outlet. (Actually, it's done the same way with a spin-on filter, but it's all inside the canister.) That's why the pin that fits in the center hole is about half an inch long, and the o-ring is at the bottom. It has to lift e.g. more than half an inch before the drain is exposed.

If that passage went anywhere important, it would fill up with oil, at least temporarily, when you pump oil into it, but it doesn't.

The concern with the wheel, assuming it is lodged in the drain passage, is that it will end up on the windage tray and be flung by a crank throw against something it can damage, or wedge between the crank and something breakable, like the crankcase.

 

Okay, with this reply, it's obvious I'm at the "bring it to a reputable MB shop who knows their stuff and let them take care of it"

I'm outside the Houston area (in Magnolia), so I'm sure there's one or two shops worth their salt (?)

 

Do you feel confident enough to take the timing cover off?

 

I've been a non-professional wrencher for 50 years (now at 64), fixing all my cars/trucks and motorcycles (gotta replace pads /flush brake fluid on Honda bike soon).

Unfortunately, I don't feel I'm at the point where I'm ready to tackle this disassembly, esp since I might not have the proper tools :/

Oh yes, I can do it, but the tools part is my downside

 

You've got nothing to loose, as long as you don't break something.

 

Spin the cylinder, hold it to your head and pull the trigger. What's the worst that could happen?
This has been going on way too long. We need closure.

 

Just spoke to owners of 2 reputable independent Mercedes repair shops - neither are willing to tackle this job.

 

Si cela peut vous aider. Désolé, je n'arrive pas a placer un fichier pdf.

 

Pourrait vous aider

 

I don't read French, but the OP doesn't have an OM651. Should be the 3.5L V6.

 

So this is the small lower oil pan "inspection cover" (not sure the tech term) bolted up where the oil pump pickup tube is located, that I am going to bolt back up.

Question : do I *have* to use the official Mercedes [gasket] sealant ? Maybe something from Loctite ?

I've read different opinions ... some say the Ford sealant is the way to go, some say Permatex, some say Loctite .
​​​​​
Thoughts?

 

I've had great results with Permatex "The Right Stuff" gasket maker for applications like that.

 

Thanks, John ... I picked this one up ... I assume it's fine

 

I'm sure it will be fine. I think there are too many products in that space. "The Right Stuff" is black. Yours is gray. Maybe otherwise the same?

 

Thanks ... I'll swap it out ... i noticed the old gasket maker still stuck on the inspection cover is black.

 

Hard to tell, is there a gasket on there, or just sealant? If it's just sealant, pit a bead of the new stuff along the inside of all the bolt holes then bolt in place, finger tight. Let it set up for a couple of hours, then torque the bolts so spec.

 

Thanks for follow-up ... yea, no true gasket, just the sealant.

Parts store didnt have the "black", but ordered and it'll be in 9am tomorrow, so will swap out then.