Repair-It

https://youtu.be/wtSdVeqQ3lU

Looks super easy and I think I actually have a leak judging by the occasional smell.

Ordered this kit.
https://www.fcpeuro.com/products/merced ... 1k#reviews

I guess this isn't a PCV. It's an oil centrifuge cover. I'm not sure I'm going to bother torqueing. Also not sure about blue thread lock. Maybe.

https://mbworld.org/forums/s-class-w221 ... oming.html

I might want to replace the centrifuge as well since I'll be in there. Just one more bolt.
https://www.youtube.com/watch?v=G4fv0i_OhOg&t=235s

Looks like the reason is the shaft wears down from riding on the cover seal. I would think a new cover with a new seal would adapt to the grooved shaft but it may be good to just replace. I could also inspect mine and if it is perfectly smooth, leave it. But may be good to have on hand for job so I'm not running around. Other than shaft wear I don't think there is any other reason to replace. This is important though because if that sealing surface isn't perfect, excess oil will go into the intake. That causes oil consumption AND failure of the flap linkage for the variable intake geometry thing. It gets gunked up and stuck. So this is solid PM.

Oh yeah, it's a LEFT HAND THREAD! Hopefully I'll remember...

$27 at my local dealer.
https://www.mercedesbenzpartsshop.com/o ... 2730100162

Here's a new bolt just for the hell of it, for a whopping $0.78.
https://www.mercedesbenzpartsshop.com/o ... 0000003495

And if I decide the hose is suspect, here is a new one for $24.
https://www.mercedesbenzpartsshop.com/o ... 2730180582

Did the cam plugs, breather cover, centrifuge, cleaned the MAF and TB. You can take the engine cover, air filter housing, MAF and intake boot under the MAF off the car all without tools.

My assessment overall:
- This was easy, fairly satisfying work
- Access to the rear of the engine was outstanding. This engine sits more than 50% in front of the front axle so I guess the V12 also goes back toward the firewall quite a bit. In any event there was plenty of room. Some M273 applications get tight back there for replacing the breather cover. Not on the W221!
- Driver's side covers seemed dry. I replaced them anyway. Just pop them out gently with a screwdriver and snap the new ones in. I oiled a little to make it easier to slide in and seat.
- Passenger side cover seemed to be seeping.
- Breather cover may have been seeping, too?
- Once breather was removed, I inspected the centrifuge seal surface and it only had a light visible wear line but nothing I could feel with my finger. I replaced the centrifuge anyway. It is a left hand thread. Torqued new one to 5 lb-ft and that seemed tight enough. It is an E8 bolt.
- Installed new breather cover. Gasket was super flat on the old one, as happens. I did not clean the sealing surface because it seemed fine and I didn't want to smear dirt all over the surface, and shredded paper towel particles or whatever.
- Torqued bolts to 5 lb-ft. They were torx.
- Then I removed the MAF and intake elbow to gain access to the TB.
- Inspected and then cleaned TB. Was able to spray and wipe. Then I sprayed some on the paper towel and held the TB open while I cleaned the edge of the blade and TB. Made it nice and clean. It was not bad.
- The intake elbow and breather tube had almost no oil in it which shocked me.
- Cleaned MAF liberally with MAF cleaner. Really douched it good. It didn't seem dirty at all.

Based on what I saw I think the minimum I could have gotten away with was one cam cover on the passenger side and just the breather cover. But I didn't know and it was good I put eyes on everything and cleaned stuff or verified that it wasn't bad.

Here are some pics.
Car fits in garage with room to spare. Driver's side covers. Removed. Installed Passenger side cover and breather cover. This is where I saw some seepage. Breather cover removed. Just 4 torx. Pulling the breather hose off was harder than expected. It is double barbed and I just needed to hit it harder with my purse. Centrifuge removed. Notice the visible wear ring though it did not feel like anything. It bolts directly to the cam and thus spins with the cam. New one. P/N is the same. Old and new breather covers. New breather installed MAF and intake boot removed. This is the TB. Intake boot. It was quite clean but I cleaned it anyway. Boot and MAF installed. No tools needed. Just be mindful of getting everything seated properly. Done! Took something on the order of 90 minutes taking my time. Some numbers from the new parts.