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Over the holidays I replaced the oil pump in my M272 and wanted to share the experience and some things I found. I was replacing it because I was trying to fix a ticking noise coming from the front passenger side of the engine. It's fairly common with these engines, and I had found someone that was claiming they had fixed it by replacing the oil pump. Since the problem appears to be oil pressure related, it was plausible. Unfortunately the ticking is still there, so no dice.
The good news is it gave me a great opportunity to reseal the oil pan which was starting to show some leakage in a few spots, as well as the front differential which was leaking a fair bit. Replacing the engine mounts was a no-brainer since the subframe had to come out too. I bought an Astro 5820 engine support bar and it worked well. I had an engine support bar from Harbor Freight but it wasn't wide enough for the W212.
Off came the brakes, steering knuckles, struts, steering rack, sway bar etc. and then the subframe
I had tried to purchase a low mileage differential off eBay just in case mine didn't look good. It was supposed to be from a '15 or so C300 but the jerk sent one from a '10 E350 and then lied about the mileage. This is what it looked like after I pulled the cover off:
Not horrible but not great. The gears and bearings didn't seem to have too much play in them and I could always clean it up a bit if needed. I didn't have time to track down another one so I hung onto it. Fortunately when I opened mine, I found it to be in amazing shape. This is what it looked like after a quick wipe-down
Just goes to show how far clean oil will get you I guess! The tolerances felt nice and tight so I went with it. I replaced the two seals the driveshafts go through as well as the sealing rings on the two covers. I ended up not replacing the input shaft seal since it looked dry and I wasn't confident I could torque the nut properly. It's not terrifically difficult to do later if need be. I also replaced the bearing on the driver side that sits between the oil pan and driveshaft. I was glad I did, it was very crunchy. It's not too difficult if you want to replace yours proactively. Just pull the driver CV axle and remove the circlip in front of the bearing. The shaft in the oil pan pulls out pretty easily and then you just press a new bearing onto the shaft. I used a shop press for this.
Getting the oil pan off wasn't too bad and I was pleased to see the engine was in equally good shape.
Things were nice and clean and all of the rods were nice and tight, no wiggle or play. I even got to get a decent look at the cylinder linings and they were all in amazing shape, no marks or scuffs at all. This was a particular relief on the front passenger cylinder since that's where the ticking was coming from. A number of dealers and mechanics have apparently blamed the ticking on scored cylinder walls, but that's not the case here.
Reinstalling the oil pan was an adventure. I had to disconnect the transmission lines and bend them slightly out of the way. After that I laid on my back and practiced guiding the oil pan into place without bumping anything. I didn't want to bump into something and screw up the sealant bead. The good news is the couple dozen practice runs paid off and I was able to seat it perfectly. A word of warning: if you buy the sealant tube from Mercedes, there isn't a nozzle included, so I had to just punch a hole in the middle. I got it done, but it was a huge pain. I probably could have used a caulking gun on the sealant tube, but without the nozzle I couldn't see well enough and it was too clumsy.
I did notice one thing while I was putting everything back together. The differential has a breather port on the top. I believe one could access it by simply removing the alternator. This is interesting because if so, it's a fairly straightforward way to refill the differential after draining it.
Maybe the next time someone removes their alternator, they could confirm or disprove this?
Start to finish, this project took me 5 days at about 8 hours a day, but I was taking my time and being conscious and deliberate about what I was doing. Yuck it up, professionals, I have no doubts you could get it done in a day.
Nice work. Good to see people not afraid to tear into these things. Still so many out there that think the "M" in Mercedes stands for "Magic" and completely lose their minds and freak out. Good for us though, keeps the used market demand/prices down.
Forgot to ask, Ultra Grey RTV for the oil pan? My go-to stuff. Doing the timing covers on my S550 with it this time. I used the black Mercedes stuff for my 212 but nearly snapped all the tendons in my hand trying to squeeze it out. Probably a bad tube but screw it, Ultra Grey is the way to go anyways. Should have used it the first time
Thanks! You do it enough and at some point you realize it's all just nuts and bolts. WIS is a pain to use but man it does a great job of spelling out everything you need to do.
I did use the black Mercedes sealant and yeah it was a huge pain to squeeze out. From what I hear that's they way it is. Ultra Grey RTV is probably fine, but I think the risk with it is it'll clog oil passages whereas with the MB stuff presumably won't. People list Loctite 5970 as the alternative and this one even comes with a nozzle but I'm sure the consistency is the same. Assuming you have the nozzle I'm almost certain you could put it into a standard caulking gun which would make application downright easy.
Unfortunately a lot of work for nothing. I own 3 m272's with anywhere from 80k to 180k miles. All make the ticking noise best heard near the passenger tire. Most of what you read on the "forums" is comically incorrect. Also, the MB sealant does come with a nozzle, obviously your dealer didn't give it to you.
Eh, I got to reseal the oil pan and front diff both which needed it, so not a complete waste of time. That shaft bearing in the oil pan was toast too. I'm not worried about the ticking per se since I haven't heard of any failures as a result. It's mostly just an embarrassing sound for the car to make and is going to make reselling it at some point a pain in the ***. I'm shocked no one has been able to pinpoint the problem (solution) yet!
Good to know about the nozzle. I got it from FCP. I'm guessing you could get some at the local parts store if need be.
Thanks! Resources like this always make it easier for me to dig into bigger projects knowing it's been done in a home garage before and seeing the gotchas they ran into.
01-18-2022, 10:25 PM
