221_S A

Hey everyone!

I'm making this post to contribute back to the w221 community by giving a view of how my w221 has so far been.

To be honest the car has been quite phenomenal. I bought it in 2019, and used it for longer trips for the most part; right now it's been driven 135k km. Initially, I was pretty intimidated by it and there were certainly checks I should've done during the pre-inspection but it's nice I didn't because I was into truly owning it and working on it. The build quality is great and there's nothing that's broken so far. Mechanically, it's held up too. I've done the regular oil changes at every 5-6000 km, and engine just purrs. I had to change the battery for it because it was old but no big deal. Initially I did take the car to the Merc dealership, but honestly if you want to keep this car, I've learned that it's very manageable if you learn to do (I previously had no experience working on cars), and if you're intidimidated, then it starts by just popping the hood everytime and just looking around. It also helps to either have the WIS/ASRA or look through this forum for official Merc guidelines on how to inspect, maintain or change a specific part.

What has required attention so far / what have I done:
1) Spark plugs, air filter, and cabin filter replacement: this is one of the easiest things one can do. The spark plugs are very accessible, and online tutorial would do! I think I did this fairly well, and though at first start it seemed to me that things were a bit "off" and that I messed something up, resetting the throttle body seemed to fix it. I'm not exactly sure what caused bad idling (it wasn't a misfire) but looking back, I should've unplugged the battery wires when I did this part. This took me 1 hour.

2) Brake fluid change: This too was fairly simple although I did screw it up because I rushed an aspect of it and I certainly didn't have all the right tools. My mistake was to allow air into the system that causes the brake pedal to be a bit soft. This took me 1.5 hours.

3) Check engine light temporarily came on: Turns out I'd forgotten to tighten the fuel cap. This almost gave me a heart attack, but thankfully it went away right after I fixed the cap.

4) Air suspension issue (I misdiagnosed it): The rear left side was seemingly sagging a bit, and given what people have said, I thought it was either the pump, bad dampener/strut, air lines microleakage, or a faulty height sensor. Reading on this form indicated that it was unlikely to be the faulty height sensor & it didn't make sense: if there is only one height sensor in the rear then one side should not sag more than the other. For this one, since I don't have the Xentry system, I had to take the car for diagnosis. Evidently no issue was found and the air pump its test (it filled 10 bars in 10 seconds), and as it turns out by garage floor isn't entirely flat LOL. That being said, I'm keeping a close eye on it.

5) Secondary air pump whistling noise: One morning the car on start starting sounding like a jet engine. Googling it indicated that it was the secondary air pump. I looked at other videos with similar complaints where they were certain that was the issue, and the sound was the same. I got a new pump; the replacement took maybe 1 hour & the car has been quiet since.

6) Sluggish driving: After initially taking the car to Mercedes in its earlier days and having them change the oil, I felt the car to be quite sluggish & "heavy" when I drove it. I should've acted on this sooner, but about a month later I checked the dipstick and it turned out that they had really over filled the oil -- I don't even know how that was possible. I used a $15 manual siphon to take out the extra oil, and I could feel the new lease of life on the car.

7) Squeaky serpentine belt issue (I failed to fix this but learned something): I heard a the noise at startup, and in reading online I saw that if the belt noise didn't increase with gas, then it was likely the belt itself. Evidently (and I could have this wrong), if the noise increased as you gassed it then it'd be a pulley. In looking under the hood, I saw two things: first, an oil leak down the engine front (more on this in a sec), and second, the belt moving just a tiny bit as it ran. Upon doing a soapy water test (as suggested by the internet), the noise would immediately go away, which also indicated that the belt was an issue. Here's the rub: Initially I was confident that I could replace it, until I got to undoing the it. Having a small ratchet and little space to turn the belt tensioner, I was able to take off the belt, but for the life of me I could not get it back on. Somewhere in the back of my mind, I knew that I didn't have the right tools, but I eventually panicked, had the car towed to the shop which charged me $200 for putting the belt back on. I knew this was steep and that putting the belt back on probably took less than 10 minutes, so I vowed to never give up again.

By this point I bought a breaker bar. I bought a 3 ton hydraulic jack, 2 jack stands, a foxwell diagnostic device, and a bunch of fundamental tools.

8) Oil leak (attempt #1): I saw that the driver side cam magnets and camshaft sensors were leaking oil. The belt tensioner, oil cooler underside, water pump and all the stuff in between were drenched in oil. It also looked like it wasn't "flowing" but the oil did look fresh and constant. I started off by using rags and a degreaser to clean some of the oil I could reach. The plan was to see if new oil would show up--it did after by a week or two. In researching it, I found out that the camshaft sensors, cam magnets, oil cooler and oil filter housing gaskets go bad and leak.

I set aside a day for this job; put the car on jack stands, took off the undercovers. Then first, I drained the coolant, which I was apprehensive about this (because I didn't have a vaccum pump to refilling it the correct way) but the upper coolant hose is made of hard plastic and needed removing. Then I stared at the engine for 2 hours, avoiding starting to do the work--which I finally got over and got to doing. The process was remarkably straight forward, and I ended up changing the gaskets, putting everything together, refilling the coolant, airing out the air bubbles, and getting the car restarted. I did get an error code shortly about the cam magnet having failed but logically that made no sense: I hadn't manhandled it, and it was working fine before. Upon immediate inspection, I found that I'd forgotten to tighten a bolt (oops!). Tightening it back up and clearing the codes fixed the issue right away. At this point I was starting to get comfortable working on the Merc.

9) Oil leak (attempt #2): A month later, I saw again that the oil was still leaking, and the new belt I had installed (for $200!) was sqeaking again. How could that be? Hadn't I fixed everything? Going through the checklist, I realized my error: I was impatient again (this is a consistent theme), and had NOT changed the oil filter housing gasket--which sucked and meant that I'd need to redo the whole process again. Okay fine: I looked up the schematics for the oil filter housing, saw that it had 6 bolts--no problem (overconfidence: another recurring theme!). Total time: 6 hours

Got the car on a ramp (parking brake on!), took off the undercovers, drained the coolant. So far everything looked fine. Took a deep breath and took off the serpentine belt (I knew I was in trouble if I couldn't get it back on, but so be it. I had time, and I wasn't going to give up). As I took each of the bolts off, I realized that I had to take the thermostat off, as well as the belt tensioner to get two bolts (I'd missed this in the instructions, and mentally made things harder for me -- since I didn't want to be taking more things off! More things meant more potential for not getting it right). Took off all the parts, cleaned them with a degreaser, changed the missed gasket (very easy to do!), put it back together. My saving grace, this time around was that I wasn't just working from the hood: when I needed to, I got under the car, which made things much easier! And better still this time it took only 2 hours!

Right now everything is working great: Drove the car for a trip (300 km round trip) and things seem smooth! I have to say that the M273 is also a terrific user-friendly engine that doesn't seem to give many problems. I know things could've been worse, but had there been turbos on the thing (e.g. like in M278), it would've been harder for me to start.

10) Ongoing issues (hopefully someone will chime for this):

--There's still an oil leak (that I saw under the engine the first time I took off the undertray) that's coating the lower oil pan. It's unclear where the oil came from: was it that it leaked from the gaskets or is there another issue? For now, given that I have "fixed" the oil leaks, I'll keep monitoring this. If new oil appears oil the pan, but not near the gaskets then I'd know there's something else that needs fixing. I was also thinking of shampooing the engine so it's super clean to find the main cause.

--Brakes: this is fairly straightforward. They're squeaking and clanking, even though the rotors and the pads are maybe only 50% used. I need to look into this, and will be doing it relatively soon.
--Transmission: I'm noticing that sometimes the shifiting is a tiny bit harsh. I plan on changing the fluid (it's time) and likely the solenoids (I've read about this a bit) if that helps.
--PCV breather system: I need to check if this working alright. Evidently if oil is mismanaged within it, it can cause super expensive issues. I plan on using this guide.

Any thoughts so far would be appreciated. Am I doing anything wrong? Does anything stand out to you?

Special thanks to Senior Leigh's Youtube channel: seeing him work on this Merc made me think "I want to be like that".

221_S A

11) Oil Change

Oh yeah, totally forgot! I also did an oil change by myself. This will sound super ridiculous but in looking through the WIS/ASRA, and their steps -- it became evident that Mercedes recommends using the oil dipstick region to change the oil. I tried using the oil drain plug but I could not find it, so given the available tools I used the same $15 hand siphone to pull out all the oil. It took me 1.5 hours, but I was able to pull out all of it! Saved me at least $100 of "labor" cost. Also changed the oil filter (replaced with Mann filter) while I was at it.

M273abc

Good luck, and give love to that S m273, little by little you will see that it is not too complicated to make repairs on it, but it is laborious. I just changed the ABC pump on my 2007 CL550. This forum is wonderful, and there are good people with knowledge willing to help. Thank you all very much. Greetings!

BOTUS

engine oil at 60C 3 mile drive and wait 20 mins - suck out with a $20 electronic pump in 6 minutes - then you can spend 20 mins you would have draining it, letting grit fall in the pathetic oil filter housing as you fight the crappy O-ring - and if asleep you can pop it out of position on reassembly and blow up the engine - never mind the filter MUST be fitted one specific way around (according to the instructions no one read) - see pathetic faint arrow on a genuine one