Hello to all my fellow mechanics who do their own maintenance,

I just tackled my oil separators along with a few other preventive maintenance items. Honestly, it wasn’t as bad as I expected—especially since I wasn’t rushed and could take my time.

If I could do one thing differently, it would be to order all the parts before starting. Waiting one to two weeks for parts really slowed everything down.

I originally tried to order the Wagner Tuning upgraded coolers, but they were out of stock at the time. I ended up going with the CSF option instead. From what I’ve seen, the Wagner units might be back in stock now, but overall I’m still satisfied with the setup.

The car has been back together for about two weeks, but I’m still waiting on a couple of small things. The plastic bumper cover brackets snapped during the process, so I’ve got replacements arriving Monday.

Overall, definitely a worthwhile job—and not nearly as intimidating as it seems.

I took a few pics along the way—I'll post them below.

 

Any more pics? Was front bumber cover removal necessary or just as a precaution?

 

I originally pulled the bumper to install a low-temp radiator, but like most projects… it turned into something bigger.

I hadn’t planned to do the oil separators yet, but one day I tried removing the oil cap with the engine running and couldn’t. That led me down the rabbit hole. I tried to order oil catch cans but never got a response from the company. After talking with a few performance shops, they still recommended adding catch cans later to prevent this issue—but since my RMS wasn’t leaking, I decided to go ahead and handle the oil separators now.

At 56k miles, it made sense to knock out a bunch of preventive maintenance while I was in there.

🛠️ What I Replaced

• Oil separator components (both sides)
• Drive belts
• Various hoses
• Wire harness adapters (oil wick fix)

Previously done:

• Spark plugs
• Transmission service @ 50k

👉 At this point, I should be in good shape for a while.

🔍 What’s Involved (Quick Overview)

This is not a small job. You’ll be working through the entire front end to gain access.

To reach the oil separators:

• The cooling fan must be removed
• The intercooler needs to be slid back
• The top metal support plate (bumper mount) has to come off

⚠️ Important Things I Learned

Cooling Fan Removal is Mandatory

There’s no way around it—you need the space to move the intercooler back.

Intercooler Access

You don’t necessarily have to fully remove it, but it must slide back enough to access the oil separators.

👉 Pro Tip:
If you’re not removing the intercooler completely, place a piece of cardboard (or similar protection) in front of the main radiator. This will help prevent accidental damage to the radiator fins while moving the intercooler around.

Bumper Brackets WILL Break

The plastic bumper mounting brackets were extremely brittle and broke easily.

👉 I recommend:

• Removing the bumper completely
• Replacing the brackets proactively

Bracket Install Tip

They’re held on with double-sided tape.

• Clean ALL old adhesive off
• Do proper prep
• Install them off the car

Trying to do this while installed would be a nightmare.

📸 Biggest Advice

Take more pictures than you think you need.

I took some—but not nearly enough.
If you end up waiting weeks for parts, you’ll forget where things go.

🧩 Parts Tip

Order EVERYTHING ahead of time.

I had delays waiting on parts, and it slowed the whole job down. If I did it again, I’d make sure every single part was on hand before starting.

🔄 Reassembly & Final Status

Got everything back together:

• Coolant system filled and bled
• Car is running smooth
• No leaks so far

I still have a few small items left to install, but everything looks good.

🚗 Next Step

Once I finish the last few pieces, I’ll take it out for a solid test drive and report back.

💭 Final Thoughts

Definitely a bigger job than expected, but not terrible if you take your time and stay organized.

If you’re already in there for cooling upgrades, it makes sense to handle this at the same time—especially around this mileage.
I

 

Did you need to drain and refill the AC refrigerant? Sound like no, but thought I'd ask for sure. I'm at 56K and thnking about doing this myself within a couple months. I was going to pay a shop to proactively change my RMS, but I think it's also time for belts and pulleys, like you said. Definitely the right time to flush the coolant.
o you think it's possible to do it without removing the bumper cover? How much more difficult would it had been with the bumper in place?
Did ay of the smaller hoses or lines need replacing or break while you were in there?
Have you ever replaced the purge valves, either prior to this or during this rehab?
Did you change the water pump and/or thermostat?
Sorry to ask so many questions.

 

Can you cut open all the plastic parts that were removed and not reinstalled, and post photos?

 

No I did not touch the a/c and yes you need to remover the bumper cover. I tried to answer your questions in my previous reply. I listed what I did and yes I did replace the water pump thermostat drive belts cam magnets and cam position sensors. Everything you see in the first post and several other hoses. I have no problem with you asking questions that's how we learning, sharing knowledge.

 

Thanks! My typing is horrible sometimes, sorry for the typos in my post.
Also, I meant to say that I plan to replace my OVSs proactively, not the RMS.

 

Awesome post & info!!
Is this a fairly accurate test to try to remove the oil cap running ? good to know pre purchasing one for sure, easy check

 

wow, thanks for sharing all of this! awesome that you got it all repaired and back to normal.

i see you are right down the road from me in Fayetteville - i should have ridden over your way and had you do mine last fall!!!!

i've got mine in at GMP now to fix a "low temperature radiator leak"...

 

Did you get the plastic bumper support brackets from Mercedes? Mine are brittle and broken as well, and I want to replace them.

 

No, it's normal to feel sucking when trying to remove the oil filler cap while the engine is running. There's always vacuum in the crankcase while the engine is running. Engine vacuum for intake is routed to create crankcase vacuum for oil vapors and any blowby. All cars have a PCV system.

 

Yes vaccum is normal but excessive vaccum is not. I called around and asked questions before a made the move to replace the oil seperators. Once I put the car back together I did the same text and I could remove the oil cap. I read somewhere that the oil seperators cause to much vaccum or to much pressure. But all I can say is I noticed a difference in my car.
As for low temp coolant that someone spoke about I would have a coolant smell sometimes coming from the drivers side and I topped off the coolant reservoir once I think mine may have been the cap. I just replaced the entire unit and so far no coolant smell.
And yes I orderd them from Mercedes. I have been ordering my parts on line because local dearships are a rip off. The plastic brackets from one local dear was like 60 .00 for one and I ordered them online and got both for 55.00 shipped Thermostat deal wante almost 700.00 online it was like 400.00.
I used MBonlineparts and MBpartscenter and MBpartsource. I had good luck with these companys.
I test drave the car today and everything seems to be well.
I also replaced the grille and I installed the Midcity engineering remote start and it works great.
I'm glad the job I did could help someone with there project.

 

While the radiator is out you should replace it with an upgrade.I did CSF for 700.00 but they don't make the aux radiator for our cars. And the Wagner tuning set is 3000.00 they were out of stock when I tried to order the kit. Better cooling is always better.

 

Folks, use numbers and not arbitrary relative statements like "excessive" when talking about vacuum.

I haven't seen an MB M17* engine measured for crankcase vacuum and I haven't seen WIS posted stating MB's specified crankcase vacuum level.

VAG/Porsche/Audi specifies 150mbar crankcase vacuum in current vee engines. This maths out to around 10-15 lbs of force pulling down on the oil fill cap. Quite noticeable.

What is the MB crankcase vacuum specification? There is one.

What are all ya'll measuring in terms of crankcase vacuum? This is a relatively easy measurement to carry out.

 

I've been looking into oil separators for my 2022 S580, and it seems like the Mercedes oil separator is a more reliable unit than some aftermarket alternatives I've seen. Anyone have any experience with the OEM system in the newer 55/53 hybrid models?

 

I undestand numbers, I just explained what my car was doing and after several videos and speaking to several Mercedes preformance shops. I decided to replace my oil seperators before my RMS failed. And all of my parts came from actual Mercedes dearlerships I learned that online parts department have better deals. I never told anyone this was the only way to check them I just said that after I could not remove my oil cap I thought my oil seperators were bad and after I replaced them I was able to remove the oil cap.

 

I noticed the same high level of vacuum on my 2019 S63 oil fill cap prior to replacing the OVS units. It is now much less vacuum. I had not taken any vacuum measurements on mine post or pre OVS replacement but I can tell that it is definitely not nearly the same level of vacuum when the car is running when I remove the oil filler cap.