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Oil Leaking from Cam Sensor or Cam Magnet into Wiring
Question for anyone who has dealt with oil leaking from one of these parts into the electrical connector attached to it which leads to destroying the entire engine harness and other vital components hooked to it. There's a current debate with senior management of a large Mercedes dealership as well as a few other dealers who are saying the oil was only leaking from the cam magnet into the wiring harness on older engines and not the M278. They also claim the cam position sensors never were leaking oil into the harness. They are saying the cam position sensor never did this. So I got to thinking since this seems to be a big problem here on the forums, that maybe we should all be filing complaints with the agency that regulates the auto industry in Germany to force Mercedes to recall this issue. I was able to find this site where you can file a complaint:
Also so we can better publicly document the extent this is happening please reply with your answer and please include what engine you have had this problem on.
Is the oil leaking from this part? Cam Magnet
Or is oil leaking from this part?Cam Position Sensor
Last edited by s550hollywood; Nov 16, 2022 at 05:44 PM.
Reason: New info
the issues isn't the harness going wrong - but its the conduit for the contaminated oil to get inside the engine ECU - and the contamination shorts something out till it goes pop - the reason you replace the harness is to get rid of the possible risk a sensor fixed car still migrating oil to the ECU
I don't know what they are but there is some bit that blocks up the outer sheath of the loom to slow down the issues for ones that didn't fill the harness fully - AKA ones that weaped do the sensors and the blocking bit (forgotten the name) - its normal across all Mercs - designed in fun they had to fix as they mistimed the self destruction and did it to themselves
my wiring harness was compromised due to oil weeping up to ECU. I recall the sensors being faulty as well as those covers ( magnets). 2012 twin turbo 5.5 liter 105k miles
A year ago I one of my camshaft position sensors went bad and the check engine light came on. I took it to a certified mechanic and he found out that one of the bank 2 sensors had gone bad and started leaking oil. He also found two other sensors were failing. Decided to replace all 4 sensors.
A few months ago I started getting the classic Mercedes startup noise. I have the check valves pre-installed as I have the latest version of the engine so it wasn't the known check valves issue. My mechanic told me that I need to have the camshaft adjusters replaced to fix the noise issue. He was pretty certain it wasn't the check valves issue.
Then about a month or so ago (6K miles after the last oil change) I got a message on the dash saying I should check the oil level. No trace of oil leakages anywhere. I'm assuming the oil leak is related to the camshaft adjusters. My car is scheduled to go in this Thursday to replace the camshaft adjusters along with a bunch of things (spark plugs, belts, oil change, ATF change, engine/tranny mounts...etc). He'll check for the leak source and let me know. Will let you know if I find out anything that could help you with your issue once I get my car back. Sorry if that doesn't help but that's all I have to say.
FWIW, the check valve issue referenced in my post can be found in bulletin LI05.10-P-056435 which has been repeatedly discussed on this forum.
Last edited by klingsor; Nov 15, 2022 at 03:27 AM.
Models 164, 171, 203, 204, 207, 209, 211, 212, 216, 219, 221, 230, 251, 463
Engines 272 and 273, MY 2005 – 2011 Camshaft Adjustment Solenoids - due to the settling properties of the seal, oil may leak from the camshaft adjustment solenoid dealers will retrofit four adapter harnesses onto the engine wiring harness. Covers any/all repairs due to damage from oil leak however, notes replacement of leaking camshaft solenoid is not permitted under consequential damage.
Approximately 557,108 vehicles are affected. Have dealer check VMI to determine if vehicle is included. Service Campaigns are covered out of warranty.
lots of things can cause excessive crankcase pressure - worn cylinders being a good one - much lower but can still be an issue, a fault in the engine breather system
both would cause things like these seals to be under more pressure than intended - does it burn oil when driving? if it never uses a drop, then a leak sounds more likely, but if its high miles, a little the worse for wear and using oil - its not fair to expected Merc to own this forever
I guess this engine came after they had modified the parts - hence its not covered under this original early fix ?
lots of things can cause excessive crankcase pressure - worn cylinders being a good one - much lower but can still be an issue, a fault in the engine breather system
both would cause things like these seals to be under more pressure than intended - does it burn oil when driving? if it never uses a drop, then a leak sounds more likely, but if its high miles, a little the worse for wear and using oil - its not fair to expected Merc to own this forever
I guess this engine came after they had modified the parts - hence its not covered under this original early fix ?
Thats cool, this post isn't about oil leaking from cam covers rather its about the cam magnets and cam sensors on the M278 leaking oil into the engine wire harness. I was fishing for others with the problem for Germany. I think between the dealers in the US and Mercedes Benz of Germany, it never happened on the M278 but at least we do know its happened on my 2013 S550 which happens to have an M278 and I know I saw others on the forums that it happened to as well on the M278. Germany showed an interest in it so I was basically trying to document other cases since they asked. I told them to google "oil in the wire harness" and they'd see topics pertaining to it surface in google.
Thats cool, this post isn't about oil leaking from cam covers rather its about the cam magnets and cam sensors on the M278 leaking oil into the engine wire harness. I was fishing for others with the problem for Germany. I think between the dealers in the US and Mercedes Benz of Germany, it never happened on the M278 but at least we do know its happened on my 2013 S550 which happens to have an M278 and I know I saw others on the forums that it happened to as well on the M278. Germany showed an interest in it so I was basically trying to document other cases since they asked. I told them to google "oil in the wire harness" and they'd see topics pertaining to it surface in google.
it most deff is not just your car my m278 100% is having this issue i recently replaced the sensors only to find they have already been replaced and i only have 60k. this is a known issue for them to act like it only effected every model up until the m278 but not including it is absurb and they know it.
on today's roads its increasing difficult to exercise an engine sufficiently - when we add turbos and go above 400 bhp the problem is now the car is twice as fast as the roads can take, and the engine longevity is is all wrong
the idea of a piston engine is the combustion gases stay where they are and we use the effort from burning fuel to push the piston down... but the sealing arrangement to do this only stays healthy if we get the engine to full operating temps and then abuse the hell out of the throttle pedal
during the running in phase and ongoing throughout the life of a healthy engine, the piston rings bed in to get a great seal which we then need to maintain. if we drive badly during the running in phase, and then land the usual operation conditions outside the correct envelope, the piston rings don't seal and or a lack of regular exercise means this sealing arrangement deteriorates
once its sub-optimal the issue readily escalates and we burn oil, under perform and push significantly more oil mist round the breather system, and the heavy pressure created in the wrong place encourages these gases to try an find a new home
A year ago I one of my camshaft position sensors went bad and the check engine light came on. I took it to a certified mechanic and he found out that one of the bank 2 sensors had gone bad and started leaking oil. He also found two other sensors were failing. Decided to replace all 4 sensors. A few months ago I started getting the classic Mercedes startup noise. I have the check valves pre-installed as I have the latest version of the engine so it wasn't the known check valves issue. My mechanic told me that I need to have the camshaft adjusters replaced to fix the noise issue. He was pretty certain it wasn't the check valves issue. Then about a month or so ago (6K miles after the last oil change) I got a message on the dash saying I should check the oil level. No trace of oil leakages anywhere. I'm assuming the oil leak is related to the camshaft adjusters. My car is scheduled to go in this Thursday to replace the camshaft adjusters along with a bunch of things (spark plugs, belts, oil change, ATF change, engine/tranny mounts...etc). He'll check for the leak source and let me know. Will let you know if I find out anything that could help you with your issue once I get my car back. Sorry if that doesn't help but that's all I have to say. FWIW, the check valve issue referenced in my post can be found in bulletin LI05.10-P-056435 which has been repeatedly discussed on this forum.
Were you able to get the work done on your car and did the camshaft adjusters fix the rattle on start up?
I would like to do this on my 15 s550 as well. I would like to do new sensors/solenoids as well as the harnesses when doing this overhaul.
Side question, I also have a G63 M157 that had a new ECU, wiring harness, and new cam sensors done about year and half ago. It has only been driven 500 miles in the year and half but would it still be beneficial to add the harness on that? I would do all four new solenoids as well since that was not done. Would the eBay jumper harness for the camshaft sensor work on the M157? On the ad it states only M278.
Is everything I have linked below what I need? Please let me know if all is correct.
I would like to do this on my 15 s550 as well. I would like to do new sensors/solenoids as well as the harnesses when doing this overhaul.
Side question, I also have a G63 M157 that had a new ECU, wiring harness, and new cam sensors done about year and half ago. It has only been driven 500 miles in the year and half but would it still be beneficial to add the harness on that? I would do all four new solenoids as well since that was not done. Would the eBay jumper harness for the camshaft sensor work on the M157? On the ad it states only M278.
Is everything I have linked below what I need? Please let me know if all is correct.
This is the aftermarket jumper harness for the camshaft position sensor.
Looks good. Keep in mind, you will have to disconnect the power steering reservoir. It might be a good idea to get a new o-ring for it and a tin of Pentosin. Also, a good set of E-Torx wrenches for those tight spots you can't get a socket into.
I haven't read this entire thread yet, but I had the same issue on my M156. Oil from the camshaft cover dripping down on to everything below. All of the wiring below was soaked in oil.
Here was the offending gasket:
I started the job to replace the cylinder head gaskets and this guy alerted me to the fact that I should also change these gaskets as well:
P0342 (Camshaft Position Sensor "A" Circuit Low) came up and now I'm reading about this M278 issue of oil leak from camshaft sensors which seems to be quite common in the M278 engine... I suspect that is what is happening. Going to get it to the shop next week to check.
I have read cases where oil goes so far into the engine harness and people have to replace hardness, ECU, O2 sensor, etc. If the camshaft. If the error has just come up what's the likelihood that the oil has gone far into the harness?
My plan is to have the mechanic confirm the presence of oil, and if the oil hasn't traveled too far up, change all cam sensors (the newer version of the sensor supposedly has a revised design?) and also add pigtail extensions to isolate the engine harness...
P0342 (Camshaft Position Sensor "A" Circuit Low) came up and now I'm reading about this M278 issue of oil leak from camshaft sensors which seems to be quite common in the M278 engine... I suspect that is what is happening. Going to get it to the shop next week to check.
I have read cases where oil goes so far into the engine harness and people have to replace hardness, ECU, O2 sensor, etc. If the camshaft. If the error has just come up what's the likelihood that the oil has gone far into the harness?
My plan is to have the mechanic confirm the presence of oil, and if the oil hasn't traveled too far up, change all cam sensors (the newer version of the sensor supposedly has a revised design?) and also add pigtail extensions to isolate the engine harness...
If the error has just appeared, lower likelihood of extensive harness saturation. No way to predict or estimate the definition of “likelihood”. After the error occurs it means oil has coated the contact pins sufficient to intermittently interrupt electrical contact.
Unplug the camshaft adjuster magnets and the camshaft position sensors and look inside the connectors. If you see oil, worry. If you don't see oil, don't worry. These parts can go bad without leaking oil. Replace the camshaft adjuster magnets and the camshaft position sensors and add all 4 extensions.
Unplug the camshaft adjuster magnets and the camshaft position sensors and look inside the connectors. If you see oil, worry. If you don't see oil, don't worry. These parts can go bad without leaking oil. Replace the camshaft adjuster magnets and the camshaft position sensors and add all 4 extensions.
I'm going to replace the camshaft sensors soon--preventive, as I'm just getting ahead of small items. Are these just plug and play, or do they require action from within Xentry like the crankshaft sensor?
crank sensor is plug and play .... as are the cam magnets
in today's world replacing one you have with new ones will likely introduce issues - everything is made to die - particularly rubbish from Germany (look at their behavior of the big issue of today - its always been only about money but now the enemy is taking over and theft from ordinary humans is completely out of control)
Please be aware that there are so-called "Oil Stop Cables" which are connected between the sensor and the plug. Basically a short extension, but it will stop the bleeding into the engine harness.
Back in the days these were a common MB part, now some privateley held shops in Germany are producing them for enthusiasts, such as Motoren Zimmer: https://shop.motorenzimmer.de/ersatz...2-m273-m274-m2
This is what MB Dealers order aswell. Once the bleeding starts, you will have a few years /miles /hours of operation until it gets critical. So no need to lose sleep over it, but get it done in time.
crank sensor is plug and play .... as are the cam magnets
in today's world replacing one you have with new ones will likely introduce issues - everything is made to die - particularly rubbish from Germany (look at their behavior of the big issue of today - its always been only about money but now the enemy is taking over and theft from ordinary humans is completely out of control)
So I'm finally getting around to changing the four camshaft sensors. I know from experience that the plastic connectors crumble like a stale cookie, and this is no exception. I literally barely touched this connector and it broke in two places. Can anyone tell me where to push on the connector to release it? It seems I have one chance, at best, to release these clips without breaking them. There's no obvious clip to squeeze, or release point that I see. I'm talking about the bracket that goes over the top of the sensor, half of which is already broken off in this photo.
Last edited by nath_h; Dec 1, 2023 at 03:12 PM.
Reason: clarity
Pull and wiggle. There is nothing securing it anymore now that the clip has broken off. Make sure you zip tie it back on if you don't replace the connector housing.
Pull and wiggle. There is nothing securing it anymore now that the clip has broken off. Make sure you zip tie it back on if you don't replace the connector housing.
Thanks. For the other three, any advice how to release the clips? It is probably hopeless though and I will have to learn how to splice wires together.
Thanks. For the other three, any advice how to release the clips? It is probably hopeless though and I will have to learn how to splice wires together.
I have a pick set from Harbor Freight that I use to lift retaining clips. It's more gentle to do it like that than to push or lift anything with a finger. If you do find those connector housings, don't splice them!!! You can release the wire internally and snap them into the new connector. The pick set will come in handy here too although I believe you can release the wire with a safety pin or small paper clip. Just make sure you put them back into the right slots.
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