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I’ve never seen a single incident similar to this with the BMW hot-V engines. It must be a Mercedes thing. At least it’s not as common except with the mbenz hot-vs
The most recent Mbenz V8 engines continue to show common expensive service items.
I meant the repair procedure. If a BMW hot V engine needed a valve cover repair it would be just as involved. Clearly the valve cover job itself isn’t a “normal” thing to need at 50k miles.
I have been told the issue won’t happen if you change the oil earlier and don’t let the separators get clogged. I’m doing 5k changes in the S580 and we’ll see.
I meant the repair procedure. If a BMW hot V engine needed a valve cover repair it would be just as involved. Clearly the valve cover job itself isn’t a “normal” thing to need at 50k miles.
I have been told the issue won’t happen if you change the oil earlier and don’t let the separators get clogged. I’m doing 5k changes in the S580 and we’ll see.
Cam cover seal failure as a result of OVS failure is an example of collateral damage, with the first step in the chain of events being OVS failure.
OVS failure --> RMS failure, mainly on M177 AMG engines
OVS failure --> cam cover seal failure. Maybe the M176 weak link is cam cover seals, in a scenario of OVS failure.
I meant the repair procedure. If a BMW hot V engine needed a valve cover repair it would be just as involved. Clearly the valve cover job itself isn’t a “normal” thing to need at 50k miles.
I have been told the issue won’t happen if you change the oil earlier and don’t let the separators get clogged. I’m doing 5k changes in the S580 and we’ll see.
5K miles oil changes seem like a good practice in this case, at least of it’s oil only, a small investment. Luckily we drive all of our cars exactly 5K miles or less in a 12 month period so that it is naturally the case, except for the GLS (we seem to be at 10K miles average per year)… I thought I would pass on the 5K in this case since it has the inline-6 instead of the hot-V
Very interesting post Joe, thanks. Do you have a part number for those newer plug boots with the rings? Sounds promising.
As I mentioned in the earlier post, I kinda think low mileage cars are more susceptible based on the small number of cases discussed here. I looked at a Carfax report on a low miles 2019 recently and it showed new plugs at 23k miles. That's oddly early to do plugs and I wonder if maybe they found oil and that's whey they changed them.
Plugs replacement might be a clue. My S560 Carfax shows no record of plugs replacement.
I'm finished oil cleanup and ready for the new plugs and boots. They arrive tomorrow. Here's the link to what I bought from FCP Euro:
I examined the vent system and blew through the system with low pressure air. I am not seeing any restriction in the pipes and separators right up through the ports in the intakes at the turbos. Found oil in the Cyls #2, 3, and 6. Cleaned that out.
I'm sure the dealer would advise getting the valve covers re-done. I need more time to see if that's worth it. My opinion is that they have a design flaw so that very expensive fix may not actually fix the problem for long. I was already contemplating pulling the front bumper off to work on the left headlight, which is causing problems with auto features. But to get to everything for the valve covers it's clear that the entire radiator frame also has to come off. Plus, the entire fuel rail and injectors would have to come out. It's beyond my DIY comfort zone. Plus, this is our daily driver so I can't afford to keep it out of service for as long as that would probably take me.
My hope is that the redesigned boots will keep oil out of the wells for a much longer period of time. We'll see how that goes....
Very interesting, please post and let us know how tightly those ribs seal up the bores. It's a stop-gap solution, but may be a very cost effective one.
Very interesting, please post and let us know how tightly those ribs seal up the bores. It's a stop-gap solution, but may be a very cost effective one.
The new plugs and boots are installed and engine is back to normal. Only question now is for how long. I did not get a photo of the boots installed. I'll try to do that when I go in to check for oil in a few weeks.
TBD ... may be that pulling and cleaning the plugs and boots periodically is the most cost-effective solution ...
Update: car ran fine for a couple of days and then the misfire returned.
When I re-installed the coil packs I flipped them across to opposite sides. Sure enough, the misfire WAS on Cyl 2 and it is now on Cyl 5. So I have a bad coil pack. It's been very hot here off and on so I'm wondering if that may be a factor.
I've heard that the coil packs can be unreliable. This is our daily driver and I don't like having to be worried every time I drive it. What I decided to do is replace all 4 coil packs. I've had good luck with aftermarket so I'm going to try a set I found on eBay.
Oil in the plug wells can cause misfires, but in this case I don't think that's what happened. It was a bad coil pack.
Update: car ran fine for a couple of days and then the misfire returned.
When I re-installed the coil packs I flipped them across to opposite sides. Sure enough, the misfire WAS on Cyl 2 and it is now on Cyl 5. So I have a bad coil pack. It's been very hot here off and on so I'm wondering if that may be a factor.
I've heard that the coil packs can be unreliable. This is our daily driver and I don't like having to be worried every time I drive it. What I decided to do is replace all 4 coil packs. I've had good luck with aftermarket so I'm going to try a set I found on eBay.
Oil in the plug wells can cause misfires, but in this case I don't think that's what happened. It was a bad coil pack.
It is known that super hot or cold weather will help a weak coil pack show its self.
I would not get aftermarket for such a part...I would always go OEM for this stuff....
Easy fix for you.
Last edited by vinflouen; Jul 17, 2025 at 12:37 AM.
Good morning guys. Put in the new ribbed spark plug boots in cylinders 1, 2, 5 and 6 (front coil pack each side). The ribs do fit nicely inside the bores.
2 and 6 had a fair bit of oil before, so these will be a good test. Today I saw they're just starting to have a little bit of oil right at the cam cover-cylinder head joint near the top of the bore. No oil on the plugs or the boots. It's about 500 miles since I changed plugs and cleaned the original boots, so glad not to see any more oil than this.
BTW, nice touch, these Mercedes OEM boots come with diaelectric grease already placed in the bottom of each boot so they'll be easier to remove in the future. Not that I plan to pull these out again anytime soon!
Last edited by Tom in Austin; Jul 18, 2025 at 11:03 AM.
It is known that super hot or cold weather will help a weak coil pack show its self.
I would not get aftermarket for such a part...I would always go OEM for this stuff....
Easy fix for you.
A failure of the coil pack at 30K miles doesn't instill my confidence in the OEM part. Have you had a bad experience with aftermarket coil packs?
The MB markup on this OEM item is unbelievable so I'm going to give aftermarket a try. I know they're newer coil packs because they have the ribbed boots.
A failure of the coil pack at 30K miles doesn't instill my confidence in the OEM part. Have you had a bad experience with aftermarket coil packs?
The MB markup on this OEM item is unbelievable so I'm going to give aftermarket a try. I know they're newer coil packs because they have the ribbed boots.
I agre@vinflouen . I've only had issues with non OEM engine management parts, not with my current car but previous S600.
Update: the new aftermarket coil packs are installed and engine is running great. Seems stronger than ever. Now it's just a question of reliability. We'll see.
Here's photos of the OEM and aftermarket coils packs for comparison.
Aftermarket coil - only markings found on it.
Aftermarket coil. They came with the new ribbed boots.
An OEM coil pack removed. Labelling has both "AMG" and "Delphi" on it. Delphi used to be the parts division of GM. The orange spot in the middle.is not on the aftermarket coils.
Good morning guys. Put in the new ribbed spark plug boots in cylinders 1, 2, 5 and 6 (front coil pack each side). The ribs do fit nicely inside the bores.
So I just had my spark plugs replaced on my 2018 S560 and I was told the valve covers need to be replaced as well because oil was leaking onto my spark plugs which was causing them to misfire. am I reading this correctly, without a warranty this could be close to a $10,000 repair job?
Originally Posted by SW20S
I'll be interested to see if other people have this issue down the line...
I will say I am big proponent for independent shops, my independent found this issue when he did my spark plugs...but I am happy that the dealer did this job.
So I just had my spark plugs replaced on my 2018 S560 and I was told the valve covers need to be replaced as well because oil was leaking onto my spark plugs which was causing them to misfire. am I reading this correctly, without a warranty this could be close to a $10,000 repair job?
At the dealer. I wouldn’t take it to the dealer if I was paying. Great opportunity to find a good independent shop.
M177 and current Porsche V-engines use cam carriers, not valve covers or cam covers.
Cam carriers are leaking oil into the spark plug bores.
Cam carrier removal to reseal requires removing the cams, because they are attached to the carrier from below/inside, which requires detaching chains and VALVETRONIC actuators. And of course the plastic and wiring parts above the cam carriers need to be removed as a first step. A pretty big job.
I am not defending dealer pricing but today’s German engines are as far from a Chevy small block as one can get.
Don't think that's exactly correct. According to my Indy, on the 176 engine the cam cover is assembled to the head and then align bored for the camshaft; there are no separate cam bearings. There is definitely a separate cover, you can see the joint to the head near the top of the plug bore and, that's exactly where the oil is leaking.
There are some videos on line showing a 4.0 engine being assembled in the factory with a cam cover being set down on top of the cams. I'm not sure how the cam cover integrates with the cam gears, chains and other parts at the front of the engine, the video isn't completely clear on that aspect.
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Don't think that's exactly correct. According to my Indy, on the 176 engine the cam cover is assembled to the head and then align bored for the camshaft; there are no separate cam bearings. There is definitely a separate cover, you can see the joint to the head near the top of the plug bore and, that's exactly where the oil is leaking.
There are some videos on line showing a 4.0 engine being assembled in the factory with a cam cover being set down on top of the cams. I'm not sure how the cam cover integrates with the cam gears, chains and other parts at the front of the engine, the video isn't completely clear on that aspect.
.
This is an interesting animation for those interested in how the M17x goes together. At 1:24 we can see the cam cover coming off, and it does appear to be a single unit from front to back with a separate piece in the front over the gears/chains ... notice too, there is a retainer of sorts near the center of each cam which prevents it from lifting up out of the head when the cover is off ...
I stand corrected. The similarity between MB M17x and VAG/Porsche EA825 and EA839 is that cam journal upper halves are in the upper cam housing aka cam carrier. I saw this in the M17x photos and didn't look deeper. My bad.
The difference between MB and VAG/Porsche is that the upper cam housing is removable on M17x, allowing cams to remain in the cylinder head. This is not possible with the Porsche engines because the cam bridge/saddle is fastened to the upper cam housing from inside.
This means cam housing oil leaks on the MB M17x seem to not require cam and VALVETRONIC removal. On the Porsche engines, chains and Variocam actuators must be removed or detached to remove the upper cam housing.
Note in the animation that cam position must be set, in order to remove the upper housing. This, combined with significant small plastic part disassembly, is what drives cost (time) to reseal the upper cam housing on this engine.
Root cause of leaking cam housing imo remains the crappy OVSs. M17x has a terrible ventilation system design. M177 LS2 suffers the worst because of highest power/tune therefore highest blowby. High blowby cannot be adequately managed with the crappy breather/OVS system MB designed. For M176 with a milder tune and less blowby, the dubious OVS system is more capable of dealing with smaller volumes of blowby gases. However, crankcase pressure is evidently still not managed properly which explains cam housing leaks.
Whether cam housing leaks are caused by crappy OVS design/crankcase overpressure or by inadequate sealant application during manufacturing (as the M276/M278/M157 engines are known for), the conclusion is the same: MB designs and builds garbage.
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