When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
My 2014 SL550 has only 27,500 so I was surprise 3 of the 4 cam sensors were leaking. All of the cam magnet connectors were bone dry. I will replace all the can sensors (fcpeuro) and add extensions I found on Amazon. I am also adding the MB extensions for the cam magnets (fcpeuro) and keeping an eye on them rather than replacing the cam magnets right now.
2018 S450 4Matic, 2021 Toyota Tundra, 2010 GL350 (sold)
Originally Posted by CaliBenzDriver
Yes indeed V6 3.0 & 3.5 TT/NA with defective Mercedes plastic CPS manufactured by Continental.
Okay, thank you. I just bought a 2018 S450 (comes up as S450v4 sometimes). It seems to be in great shape and has zero leaks right now.
I am NOT very mechanically minded and MB is especially new to me. To make that worse my brain is in a lot of fog due to … I hope … chemotherapy treatments.
Is there anyone here who might be so kind as to send me a link where I can purchase these for my particular car, which I think has the M276 engine? I have an independent MB mechanic looking at the car soon and I’d like to take care of this so it’s one less thing to worry about.
I hate to ask for help, but I have also reached a point where I know I better start asking for help to avoid compounding or bringing on new issues right now.
I had an oil leak coming from one of my cam position sensors so I replaced the o-ring and it fixed the oil leak. I bought a few more o-rings at the same time since they were cheap, Have yet to need them though.
The cam sensor plastic injection molded body fails allowing oil infiltration inside the sensors, from where it is wicked along the electrical contacts, through the connector and along the harness. Changing o-rings does not solve oil in the harness.
There are photos on this site showing failed sensor bodies.
The cam sensor plastic injection molded body fails allowing oil infiltration inside the sensors, from where it is wicked along the electrical contacts, through the connector and along the harness. Changing o-rings does not solve oil in the harness.
There are photos on this site showing failed sensor bodies.
Anyone have M176 w/ EQ boost engine diagram handy? Took a peek around in the GLE briefly and it didnt jump out at me, any location info would be helpful thx.
On the M176 it looks like the intercoolers are blocking access to the sensors so it's going to be a bit more difficult to do. I'm still researching it.
Anyone have info on the M176? This is the 4.0L V8 in the S560.
They don't mention the camshaft sensor leaks, but they do mention something that can be a potential cause. One of the known problems is the oil separators, which are in the path of crankcase ventilation. If those clog it will cause excessive crankcase pressure, which will push oil out of seals and could also cause excessive oil consumption. Seems likely that this is also a potential cause for the camshaft sensor leaks.
Unfortunately, these engines are tightly packed and very difficult to work on. If you're willing to remove the intercoolers, then you can get access to the cam sensors, cam magnets, and oil separators.
What my mechanic said.
Yes but we have found it’s not coming from cam magnets like he said. At the dealer, among all of us technicians, we have found that the oil is feeding into the harness from the cam sensors, which is a different part than what he is showing. We have also only found it to be really bad on the 276 engine and the 278 engine. I believe your white S class has the 278 engine in it. Your other cars are not affected by this. What I suggest is at around 80,000 miles we replace the cam sensors.
I stumbled on this post, and checked my 80k mile 278, and no issues with Magnets connectors (on front of heads), but my position sensors (on top of heads) were all wet with oil. Ordered new set of 4 Genuine MB from AutohausAZ. FCPEuro sells a pigtail kit with the 4 magnets and pigtails, but didnt find pigtails for position sensors. One of their videos indicates older models work fine, but didnt find part numbers (I like to stick with MB parts if possible). 2 questions. 1) Replacing the position sensors with current ones, will that fix the wire leak for the foreseeable future, so no real need for pigtails? 2) anyone have the MB part number for the cam position sensor pigtails?
I stumbled on this post, and checked my 80k mile 278, and no issues with Magnets connectors (on front of heads), but my position sensors (on top of heads) were all wet with oil. Ordered new set of 4 Genuine MB from AutohausAZ. FCPEuro sells a pigtail kit with the 4 magnets and pigtails, but didnt find pigtails for position sensors. One of their videos indicates older models work fine, but didnt find part numbers (I like to stick with MB parts if possible).
2 questions.
1) Replacing the position sensors with current ones, will that fix the wire leak for the foreseeable future, so no real need for pigtails?
2) anyone have the MB part number for the cam position sensor pigtails?
Nope, new Continental CPS were shown to begin leaking on schedule from ~25kMi.
The previous engines used an ALL SEALED sensor that could never leak.
A quarter In. longer version was designed with slot openings to LEAK.
The new product sales are performing much better at $50Ea.
Last edited by CaliBenzDriver; Jan 5, 2025 at 12:42 PM.
Found this thread yesterday and went home after work and checked my MY14 SL 550 w/278. 53,000 miles. Add me to the list.
Sure enough, the first sensor plug I pulled off was covered in oil. I didn't go any further as I just pulled the easiest plug.
Will be ordering the parts today with pigtails and will be replacing everything before I move the car again.
Hoping it hasn't reached the ECU yet. Fingers crossed !
I will be checking my wife's MY19 GLC 43 AMG w/276 this weekend. Looks like I may be completing this task twice.
Last edited by TinManMike; Jan 7, 2025 at 07:27 AM.
If you're car is running well and you have no issues, it is time to install pigtail extensions onto your cam sensors and cam phasers.
I have a 2015 S550 with 72k miles on it. I have read extensively on the infamous "oil in my wire harness" issue that plagues the M278 engine (the Benz "550" engine in most late-model vehicles). For those who don't know, the problem is caused by oil that leaks from the cam phasers and cam sensors into the main engine wire harness. This oil travels along the sheathing and damages many downstream sensors and ultimately the ECU. Many M278 owners have had to replace the entire engine wiring harness as a result of this issue, which is about a $11,000 repair at an MB dealership.
MB has updated the cam phaser part numbers, but unfortunately the new parts still leak (as documented by my indy). One knowledgeable poster on this forum noted that "it is usually the cam sensors that leak, but everyone seem pre-occupied with the phasers".
I decided stay one step ahead of any issues are replace both the cam phasers and cam sensors on my car, which was running beautifully. This runs about $450 for genuine MB parts. And can you guess what I found? Oil had leaked past every one of my cam sensors and cam phasers. The wiring harness to the cam sensors was oily to touch, while the phasers were not yet. Hoping I can still avoid a huge problem, I did replace all of the parts. My ECU appears unaffected (some posters had visual oil on their ECU connections).
It is a small, sacrificial pigtail (extender) that can can be installed onto your cam phasers and cam sensors. It serves as medium so that oil does not continue spreading along the main engine harness.
MB does make a part for the cam phasers that comes off an older MB engine, but they do NOT make the part for the cam sensors which in my experience are much more prone to leaking. What I have posted above is the only solution. Fortunately I am your guinea pig, as I am now using them in my car and they are very good quality. In fact, quality is as good as the genuine MB pigtails for the cam phasers which I am using.
TLDR: Do yourself a favor, buy the above kit and spend 30 min installing it to avoid a very costly repair.
Great article!
Inspired by this thread, today I checked my 2015 Mercedes S550 with 49K miles. Out of four camshaft position sensor connectors, three were totally dry and normal, while fourth connector near the windshield washer fluid bottle showed slight signs of oil residue. All four connectors on Camshaft Adjuster magnets were totally dry and normal.
Now do you recommend changing all four Camshaft position sensors or just the one that has oil film on it? My gut feel and technical judgment says just replace one oil wet sensor and don't fix what's not broken. Also old sensor quality is probably better than the new.
I also want to install the 8 pigtails on https://www.ebay.com/itm/170915481725 as recommended. The eBay page vehicle compatibility check says this item does not fit my vehicle but says it fits many Mercedes models and in its list of vehicles also list 2015 S550 Coupe. I have asked the seller to check my VIN # and confirm if its an exact fitment, but is still waiting for the seller response. You could also buy a better quality similar pigtail harness at Amazon for $37, that accurately confirms the vehicle fitment. Here is the Amazon product link https://a.co/d/9U9FkMO
Let me know if any of you have any recommendation for me. Thanks!
Last edited by amriyaz; Jul 27, 2025 at 10:20 PM.
Reason: Amazon equivalent pigtail harness
Finally decided to order 8-piece pigtail harnesses from Amazon.
Based on my research and talking to Mercedes technician, ordered all four new Camshaft position sensors, by Bremi, 2769051000, SKU: BMI-60558 from FCP Euro. They are exact OEM part of Mercedes brand but are reported to be better and last longer and leak less and are made in Germany as compared to Hungry. Also I was told always to replace all four identical position sensors from the same manufacturer for consistency and predictability, as in the long run it works better.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
