I will take photos when they get replaced.
It is under approved MB warranty but seemingly I have a fight on my hands to get them to do anything more than the bare minimum.
It's a 2015 M157 E63 with 31k on the clock and I've noticed the issue since buying two years ago.

 

I have inspected the sensors and cleaned the oil residue out. There appear to be no cracks that I can see in the plastic so I assume as is the general consensus, that the oil makes it's
way between the electrical pin and the plastic housing.
I will get pics when the time comes.

 

Thanks for the photos @Hakon74

Will you, or did you, replace the cam position sensors? A theory is that the black plastic housing, that contains the sensing element and is exposed to oil, cracks. Then, as you mentioned, oil travels into and through the sensor up the electrical contacts and into the harness.

Visual confirmation of a cracked sensor body would confirm the notion. The sensor body is not visible from outside the engine and the sensor needs to be removed and fully cleaned to see a crack, if one exists.

 

They will all be replaced in the next week or so. I will make sure the old ones get returned and grab some photos.....better

 

We don't know what the reimbursement rate from M-B to the Dealer is, for warranty work. It used to be generous, and Dealers preferred a warranty reimbursement instead of Customer Pay, since they made more money on Warranty.
Can you compare the rates in your market? I'll try to verify next time I talk to my Service Manager. (It varies by market.)

 

@mikapen How would that information be gathered?

 

From my point of view I don't think the dealers over here are that transparent.
But interesting thoughts on reduced payout of warranty work,,,,,,which may go someway to explain why they are recommending the warranty will cover the simple things and getting me to pay for the rest.

 

The price that dealers are paid for warranty work from manufacturers in unknowable to the general public. It’s one way that carmakers incentivize dealers to push back on the consumer and delay or deny warranty claims. If the dealer knows they won’t make good margin on warranty work, they will make efforts to resist doing it. It’s the agency problem in operation.

 

Ask your Service Manager, as I said above. I haven't had a chance.

In the past, German manufacturers were quite generous with their reimbursement rates, so your previous comments that Dealers prefer customer-pay may not be true.
Let us know what you find out. Thanks.

 

That's a specious claim. You don't know, so ask before you pass judgement.

 

Not worth the breath to reply.

 

Some pictures of the cam sensors.
Seemingly no cracks but it looks as if the oil ingress is just below the pins.

 

@Hakon74 Thanks, these are great photos. Is it possible to post a photo of the sensing face (axial view at the circular end of the sensor exposed to the camshaft)?

The wet pins show that oil has entered the interior of the sensor, and is wicking up through the electrical contacts, which are not sealed. They are not sealed because the sensor is designed to not allow oil inside, under ideal conditions. Clearly the ideal conditions are not met, as evidenced by leaking.

I'm thinking a crack is the black injection molded plastic sensor body, exposed to oil. This means the crack, if one exists, is below the o-ring. "Below" means the direction towards the camshaft and away from the exterior harness connector.

To find a crack requires the sensor to be as perfectly clean and free of oil as possible, using a bright light and close inspection lenses, for people needing such lenses. As I do!

Look very carefully around the sensing tip and the radiused corners of the plastic injection molded housing. The oil got into the sensor somehow, the mission is to find how it penetrated the sensor housing.

 

Not great pics but no clear evidence of any cracks.
Could it be from the little windows on the side ?
Either way I've just ordered 4 replacements, so will compare when they arrive.

 

Thanks @Hakon74 . The crack in my estimation is near the most stressed location - whether the stress comes from chemical, thermal or mechanical/vibration. Any of the radii could be suspect, and the windows as you mention. The root cause could be poor choice of resin chemistry/formulation, injection molding quality defect, or insufficient/too thin material in the nominal design.

If you can take the same photos of the new sensor, compared with the old, it will help identify what has changed between the part numbers. The changes is where I would look for the failure on the old sensor.

 

New sensors arrived, still made by Continental.....no real changes it seems. Green o-ring looks nice though.

 

Yep, looks nice. MB could have made changes not visible to the casual observer such as plastic chemistry/formulation, injection molding parameters (time, pressure), very small changes in corner radii, slight thickening of the sensor body walls, etc.

@Hakon74 Do the connector internals (pins area) look different? Obviously it needs to fit the existing harness, but are there details in the epoxy potting or other things that look different? Can you post a photo of the "window" with the connector pointing to the left in the photo? That would show the same side of the sensor as your earlier photo of the removed sensor. Thanks.

 

I think I can see (under magnification) an issue within the window of the sensor. It looks as if what's inside the window is a different material to the outer casing with a resulting interface or failed interface.
It's not clear but this may the point of ingress.
The exit point seems to be just below the pin connectors in what looks like a fine junction between these inner components and outer casing.
I've rinsed the old ones in brake cleaner the most leaky of all the sensors allows the cleaner through, no trouble at all.
First pic is old sensor, challenge to get the light and focus at the same time, but I think it's clear that there is a rectangular junction around the pins and the leak via it.


New sensors. Appears to be slightly different around the pins

 

The oblong window adjacent to the "Continental" word looks different. The bottom of the 3-pin cavity shows where the injection mold has been machined. These are differences that are apparent after a cursory review. MB clearly changed the sensors.

 

https://www.facebook.com/groups/2261...340/?ref=share

 

Joined the group and agree MB needs to fix this issue

 

Does this also apply to the driver's side? I'd assume they are routed similarly, but sometimes that is not the case.

 

Just going through this thread is this problem only found on the M278 or also on the M276? Is this now a "A MUST" service protocol to inspect these connectors once in a while as a preventive maintenance?

 

Oil in the harness affects the contemporaneous engines M274, M276 and M278/M157.

It is a must to inspect the 8 connectors over time.

Early stage oil in harness is recoverable by replacing cam position sensors and cam magnets with the latest part numbers.

More advanced oil in harness may additionally require engine wire harness replacement and ECU replacement.

O2 sensors have been reported as affected by oil in harness but this seems less common.

 

YES. Inspect now and replace if you have older part numbers. It is usually overlooked, even at the dealers...