M176 S560 Valve cover gasket leak
MBWorld Fanatic!
Joined: Nov 2015
Posts: 1,685
Likes: 820
From: Newcastle, WA
2019 S63 4Matic+, 2018 E400 Cabrio, wardens car.
The OVS is the PVC system for the M17X motor platform. On the 18-20 LS1 M177 versions of this motor, there has been a a lot of noise around the OVS system getting clogged across MB product families but primarily the AMG 63 variants that have encountered clogging of these OVS parts that cause excessive crankcase pressure, either positive or negative. When this happens, seals start either blowing out or sucking in and then failing, causing leaks. Predominantly it has been the RMS where the leaks happen but there are cases with the valve cover gaskets leak as well. I discovered this week that you can probably deduce pretty quickly if you have clogged OVS devices by trying to open the oil fill cap while the car is running. In my case, I could not even turn the cap. Once I shut the car off it twisted off with little to no force. I then took a pair of pliers and removed the cap with that and it sounded like a massive amount of vacuum was released and the sucking sound continued a little but the motor still ran fine. My mechanic told me today that this is definitely not right and 100% is clogged OVS devices that are not letting excess vacuum dissipate out from the crankcase. Luckily I have checked with Fidelity and this is something that will be repaired under my warranty, I am just glad I caught this before it did any further damage, at least I hope so. There is a new design of the OVS that was introduced a few years ago and the issues do not seem as prevalent with the newer design but we shall see.
Last edited by superpop; Jan 7, 2026 at 07:02 PM.
Junior Member
Joined: Dec 2025
Posts: 56
Likes: 21
From: Phoenix east valley
2018 MB S560, 2018 Ford F150
The OVS is the PVC system for the M17X motor platform. On the 18-20 LS1 M177 versions of this motor, there has been a a lot of noise around the OVS system getting clogged across MB product families but primarily the AMG 63 variants that have encountered clogging of these OVS parts that cause excessive crankcase pressure, either positive or negative. When this happens, seals start either blowing out or sucking in and then failing, causing leaks. Predominantly it has been the RMS where the leaks happen but there are cases with the valve cover gaskets leak as well. I discovered this week that you can probably deduce pretty quickly if you have clogged OVS devices by trying to open the oil fill cap while the car is running. In my case, I could not even turn the cap. Once I shut the car off it twisted off with little to no force. I then took a pair of pliers and removed the cap with that and it sounded like a massive amount of vacuum was released and the sucking sound continued a little but the motor still ran fine. My mechanic told me today that this is definitely not right and 100% is clogged OVS devices that are not letting excess vacuum dissipate out from the crankcase. Luckily I have checked with Fidelity and this is something that will be repaired under my warranty, I am just glad I caught this before it did any further damage, at least I hope so. There is a new design of the OVS that was introduced a few years ago and the issues do not seem as prevalent with the newer design but we shall see.
MBWorld Fanatic!
Joined: Aug 2017
Posts: 1,696
Likes: 521
2019 S560, 2015 Honda Civic Hybrid
Changing the OSVs is a lengthy and expensive job. It's very unlikely that anyone changed yours if they could avoid it, since it's relatively easy and inexpensive to just replace or clean the plugs and plug boots to make the car run properly. As I mentioned in an earlier post, my dealer and independent acted as though they weren't even aware that a flaw in crankcase ventilation was a root cause for oil leaks.
My independent did do some research looking for a spec or measurement method for crankcase pressure and said he couldn't find anything that he could use to determine whether my car had such an issue.
My independent did do some research looking for a spec or measurement method for crankcase pressure and said he couldn't find anything that he could use to determine whether my car had such an issue.
Last edited by Tom in Austin; Jan 8, 2026 at 09:38 AM.
Thread Starter
MBWorld Fanatic!
Joined: Jun 2015
Posts: 9,062
Likes: 4,565
From: Maryland
2024 S580
I think you need a new dealer and independent if they didn't realize that was an issue. Nierher my dealer or independent was surprised at all. The independent found it when he did the plugs and referred me to the dealer since it was under warranty still, he knew immediately what it was and so did the dealer. Both described the OSVs and the crankcase pressure.
Senior Member
Joined: Apr 2025
Posts: 487
Likes: 203
From: Lowcountry, GA
'25 S580
Quick question to experts here;
- I understand PCV is actuated by intake vacuum/pressure, then what's controlling the OSV operation?
- What's the main cause of OSV failures? Contaminated oil-sludge?
I'm trying to understand what benefits the 5k mile oil changes serve
- I understand PCV is actuated by intake vacuum/pressure, then what's controlling the OSV operation?
- What's the main cause of OSV failures? Contaminated oil-sludge?
I'm trying to understand what benefits the 5k mile oil changes serve
Senior Member
Joined: Apr 2025
Posts: 487
Likes: 203
From: Lowcountry, GA
'25 S580
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Junior Member
Joined: Dec 2025
Posts: 56
Likes: 21
From: Phoenix east valley
2018 MB S560, 2018 Ford F150
Quick question to experts here;
- I understand PCV is actuated by intake vacuum/pressure, then what's controlling the OSV operation?
- What's the main cause of OSV failures? Contaminated oil-sludge?
I'm trying to understand what benefits the 5k mile oil changes serve
- I understand PCV is actuated by intake vacuum/pressure, then what's controlling the OSV operation?
- What's the main cause of OSV failures? Contaminated oil-sludge?
I'm trying to understand what benefits the 5k mile oil changes serve
Junior Member
Joined: Dec 2025
Posts: 56
Likes: 21
From: Phoenix east valley
2018 MB S560, 2018 Ford F150
The OVS is the PVC system for the M17X motor platform. On the 18-20 LS1 M177 versions of this motor, there has been a a lot of noise around the OVS system getting clogged across MB product families but primarily the AMG 63 variants that have encountered clogging of these OVS parts that cause excessive crankcase pressure, either positive or negative. When this happens, seals start either blowing out or sucking in and then failing, causing leaks. Predominantly it has been the RMS where the leaks happen but there are cases with the valve cover gaskets leak as well. I discovered this week that you can probably deduce pretty quickly if you have clogged OVS devices by trying to open the oil fill cap while the car is running. In my case, I could not even turn the cap. Once I shut the car off it twisted off with little to no force. I then took a pair of pliers and removed the cap with that and it sounded like a massive amount of vacuum was released and the sucking sound continued a little but the motor still ran fine. My mechanic told me today that this is definitely not right and 100% is clogged OVS devices that are not letting excess vacuum dissipate out from the crankcase. Luckily I have checked with Fidelity and this is something that will be repaired under my warranty, I am just glad I caught this before it did any further damage, at least I hope so. There is a new design of the OVS that was introduced a few years ago and the issues do not seem as prevalent with the newer design but we shall see.
Junior Member
Joined: Sep 2021
Posts: 40
Likes: 12
From: San Jose, CA
2020 GLC300 4matic, 2017 C300 4matic
My service advisor said, oil separators are good but he said that before taking parts apart.
Dealer ordered some parts beginning of the week, and yesterday they started working on the car.
I especially asked them to replace OVS. If they wont, I will pay them to do it unless they dont charge me for extra labor
I was hearing slight squeak noise around 20-25 mph not related to gear or rpm. I heard Clogged OVS could make that noise.
Also when I check oil separators on mbparts website, they are not updated. It doesnt show “replaces” old part number, something like that. Most updated parts shows old part numbers and shows “replaces”
My car was dropped off on New Year’s Eve. Hopefully It would be ready next week
I will share the invoice
Dealer ordered some parts beginning of the week, and yesterday they started working on the car.
I especially asked them to replace OVS. If they wont, I will pay them to do it unless they dont charge me for extra labor
I was hearing slight squeak noise around 20-25 mph not related to gear or rpm. I heard Clogged OVS could make that noise.
Also when I check oil separators on mbparts website, they are not updated. It doesnt show “replaces” old part number, something like that. Most updated parts shows old part numbers and shows “replaces”
My car was dropped off on New Year’s Eve. Hopefully It would be ready next week
I will share the invoice
Junior Member
Joined: Sep 2021
Posts: 40
Likes: 12
From: San Jose, CA
2020 GLC300 4matic, 2017 C300 4matic
Dealer asked me to replace spark plugs again for $200. I told them I replaced them already but they said they are all have oil on them. For $200 I told them to replace just for peace of mind. Also I will pay Oil Separators and I was told no additional labor for them too.
Junior Member
Joined: Dec 2025
Posts: 56
Likes: 21
From: Phoenix east valley
2018 MB S560, 2018 Ford F150
Agree, that is a good move!
MBWorld Fanatic!
Joined: Jul 2013
Posts: 4,830
Likes: 772
From: Venice Florida
2018 S560
Sounds like some people still have honest dealers. Seems like here in Florida the ones I used have all gone bad. When I got quoted like 18,000.00 dollars just because the dealer in Clearwater told me there was just a slight seepage of oil on the right front strut but there never has been any oil on the garage floor, the fluid on the dipstick for the MBC was full that was pretty much the beginning of the end for me with the 2018 S560. I figured probably the OVS would be next as I was over 82K miles and plus the motor mounts had never been done nor the water pump or thermostat. Even those things are big $$$ jobs if your out of warrantee. Even if I was able to work on things I just don't have the time, I'm busy with other stuff and these cars seem to be super labor intensive. So I traded in the car for a brand new 2025 Audi Allroad with a full 4 year factory warranty. I'm back and fourth between New England and Florida and just could not trust the Benz anymore nor the dealers and independent shops around here it's real hit or miss. Once thousands of dollars are put into the car you never get it back. It's kinda a shame as I'd just replaced the lower seat upholstery and the car was totally up to date with service although I figured it was only gonna be another 18K miles before I was looking at a trans oil change again (1400) and Spark plugs (1000) and maybe a coil or two and maybe new batteries eventually. I think the main battery in the trunk was still the original surprisingly and over 8 years old.
MBWorld Fanatic!
Joined: Oct 2002
Posts: 4,975
Likes: 1,343
From: Cincinnati
2010 E350 4Matic
An example is my independent rebuilt my transfer case for $2500 when the dealer would only replace it as part of the transmission for $8000
Last edited by MBNUT1; Jan 14, 2026 at 09:40 AM.
Junior Member
Joined: Jan 2026
Posts: 62
Likes: 22
2020 S560 4matic. 2017 Z06 convertible.
Boosted engines should have an oil catch can. It essentially does the same job as the OVS but a catch can never goes bad. Just drain it regularly. I have multiple boosted cars. Z06, 800hp centrifical boosted, etc. They all have catch cans and never leak oil. I'm talking years with no leaks.
My preferred go to catch can is the Mighty Mouse. It's worth the investment. I think after reading this thread I'm going to put one on my 560 too.
Great information in here!
My preferred go to catch can is the Mighty Mouse. It's worth the investment. I think after reading this thread I'm going to put one on my 560 too.
Great information in here!
Junior Member
Joined: Dec 2025
Posts: 56
Likes: 21
From: Phoenix east valley
2018 MB S560, 2018 Ford F150
Boosted engines should have an oil catch can. It essentially does the same job as the OVS but a catch can never goes bad. Just drain it regularly. I have multiple boosted cars. Z06, 800hp centrifical boosted, etc. They all have catch cans and never leak oil. I'm talking years with no leaks.
My preferred go to catch can is the Mighty Mouse. It's worth the investment. I think after reading this thread I'm going to put one on my 560 too.
Great information in here!
My preferred go to catch can is the Mighty Mouse. It's worth the investment. I think after reading this thread I'm going to put one on my 560 too.
Great information in here!
MBWorld Fanatic!
Joined: Aug 2017
Posts: 1,696
Likes: 521
2019 S560, 2015 Honda Civic Hybrid
This makes sense, managing oil vapor and crankcase ventilation doesn't have to be wildly complicated, many cars including my 1994 Porsche benefited from relatively simple aftermarket catch can solutions.
MBWorld Fanatic!
Joined: Aug 2007
Posts: 1,823
Likes: 792
From: Pacific Northwest
2001 S600 V12 Sold, 2011 Jaguar XFR Sold, 2017 S550 4-Matic, 2018 S63 AMG Sedan
Boosted engines should have an oil catch can. It essentially does the same job as the OVS but a catch can never goes bad. Just drain it regularly. I have multiple boosted cars. Z06, 800hp centrifical boosted, etc. They all have catch cans and never leak oil. I'm talking years with no leaks.
My preferred go to catch can is the Mighty Mouse. It's worth the investment. I think after reading this thread I'm going to put one on my 560 too.
Great information in here!
My preferred go to catch can is the Mighty Mouse. It's worth the investment. I think after reading this thread I'm going to put one on my 560 too.
Great information in here!
Junior Member
Joined: Jan 2026
Posts: 62
Likes: 22
2020 S560 4matic. 2017 Z06 convertible.
it's been 4 years since my build on that car. Since then, not a single leak. Case closed.
Elite also makes a good quality catch can. I just prefer the MM cause it's easier to install and maintain. I'm looking into converting the ovs to a catch can now with some local MB guys.
MBWorld Fanatic!
Joined: Nov 2015
Posts: 1,685
Likes: 820
From: Newcastle, WA
2019 S63 4Matic+, 2018 E400 Cabrio, wardens car.
It is my understanding that you need a pretty specific Catch Can set up to avoid tripping a CEL or code. 63 motorsports has one for the M177/M178 motors but it is not cheap at around 1600 plus install. I think they have redesigned the OVS system in the M17X motors though to remediate the clogging issues with the original OVS. At least I hope this is the case as I am getting the new ones installed in my car now.
