Repair-It

Decided to pull that oil pan, after draining the 9 quarts of oil.

The sensor is under there. I was able to remove the two float bolts but the plug bolt is so far in. I need to pull the oil pickup to be able to get my hand in there. Before I do that I need to get the right O-ring because this car is as good as dead in the water without a new O-ring. You don't put a used oil pickup O-ring back in. That is asking for oil pressure issues. The dealer should get it tomorrow. Then I can continue and this should be pretty easy. I'm just glad they provided an access cover for this stuff.

Got the two O-rings. Looks like the smaller nitrile one fits. I tried to squeeze the thicker Viton seal in as I know that's a much better O-ring material but it just didn't want to go in and I didn't want to break something.

With the pickup out of the way it was definitely easier to tighten the plug bolt on the oil level sensor. Still annoying as I still had to do it with a closed end wrench (fun fact: a 5/16" works on an E10 head). But I got the sensor back on.

Then I did the pickup. Also easy. Wish the black O-ring fit a little tighter but oh well. The old one was square and starting to get fairly hard (not totally brittle yet). Kind of seems like a service item you should do every 10 years. I know it's a big deal on my E55 and NOT easy to get to on that car.

Oh, I found these metal shards in the oil pump pickup screen:
My best guess is this is remnants from that mystery cam replacement that happened when the car was brand new. I am not sure if this is bearing material (kind of looks like it) but there does not seem to be anything wrong with the engine so I am just going to do the right thing and pretend I didn't see it.

Also it took a long time to clean off the pan and cover surfaces to prep them for new RTV. Maybe the most annoying part of the job. But I got it done, goobered some stuff on the pan cover, smeared it with a clean glove finger and slapped it on. Torqued to 10 lb-ft in some kind of pattern. I let it cure for an hour (went on my walk) and during that time it occured to me that I did not put the drain plug back. That was correct, I had not. Geez. So I put on a new copper washer and put the drain plug back. 25 lb-ft is what I did. Then I attempted to dump 9 quarts of oil in.

I say attempted because this is where I made my patented stupid mistake. I added a full 5 quart jug of M1 0W-40. Then I picked up the other jug and added 4 quarts. Only problem was this:
Yup I grabbed the 5W-30. So now I have to do another oil change but honestly it's not a bad thing because I was working inside the oil pan and despite my attempts to be neat and tidy I am sure I got some crap in there that was on my gloves or something. So I'll do another oil change soon and chalk it up as a flush.

But the good news is everything seems good. No leaks. Once I do the second oil change I'll worry about checking the oil level on the dipstick, hopefully see a perfect oil level, and then I guess hope I don't see the "check oil" message until the oil is actually a quart low or whatever.

https://youtu.be/TpJ7TLfLlcw

Only video on the entire internet for this on the 4Matic cars as far as I can tell.

Changed the oil again with the correct M1 0W-40. 9 quarts.

Checked the oil outside the garage so not totally level but fairly level. Without O-ring, it was about halfway between max and min. Waited about 10 minutes. The minimum 5 minutes would be even lower I guess. I expected it at max. Maybe that's where it is supposed to be after an oil change. I think Mercedes doesn't understand dipsticks.

So I guess from here I just run it. I will probably check before we leave for Orlando and then at gas stations. I will have to remove the O-ring to get the proper reading. Unfortunately I have no clue what the oil consumption rate is with this car so maybe after some initial checking I can settle down and get comfortable with it. That is assuming the check oil warning doesn't come on! If not then I guess I fixed it and the thread is over. I'll update.

Good news: the oil consumption rate is zero. That is exactly where the oil level was after 5100 miles and I verified 9 quarts were removed from the engine.

Closing in on another 5,000 miles. Haven't so much as touched the dipstick. No warnings about low oil. At this point I'll just ride it out and check before next change. I assume my results will be the same - no consumption. And as a result I should probably stick with the M1 0W-40 euro.