PC69

I have a 2012 E550 with M278 engine. My mechanic found oil in the wiring harness and He tried to clean it multiple times but still couldn't resolve the problem. He told me I need to replace the wiring harness. How much is the wiring harness? What about the labor cost?

oldmots

I suggest cleaning the harness and correcting the leak so it stops happening. There's no sense replacing the harness just to let it fill up again. You should be able to spray Brakleen through the same route the oil took. Keep in mind that oil is not conductive, so it shouldn't matter that electrical contacts get oily. I even use dielectric grease on spark plug boots. I have seen spark plug wells full of oil with no effects.

chassis

Hundreds of posts on this on the site.

Offenders are cam position sensors and cam magnets.

Victims are ECU, O2 sensors, injectors and coils.

If caught early enough, new cam sensors and magnets, plus a thorough cleaning will solve it.

If not caught early enough, a new ECU and other victim parts need replaced, plus the engine harness. This is solvable, but the cost and effort to do so depends on how far the problem has developed.

Mr. Toad

Does anyone know which models this issue affects? I have a 2016 e400 couple with a twin turbo V6.

chassis

M274, M276, M278 and M157 engines.

M274 seems least affected based on posts on this site.

Used on:
W212 and W213 E-Class
W205, maybe W204 but not sure C-Class
166 all variants
X204 GLK
X253 GLC
W222 S-Class

Time frame is the two thousand teens.

Mr. Toad

So I'm in the clear with a W207?

syspklc53

See service campaign 2012070002 - The model year stops at 2011 ???
I have a 2013 E550 4M (in the shop now) - they found oil in my wiring harness after I asked them to replace my Camshaft Position Sensors (4) and my Camshaft Solenoids (4)

chassis

No, any vehicle with the above referenced engines can be affected by oil in the harness. I am not aware of each and every platform where MB used these engines, I listed the ones I am aware of. The list is not exhaustive but rather representative.

The M274/276/278/157 are from the same generation and have a large collection of commodity bits and pieces shared among them. For example, cam position sensors.

Mr. Toad

The campaign document indeed indicates "Model Years 2005 - 2011". Are they covering your 2013 model?

Does anyone know why the campaign ends with 2011, e.g., did subsequent model years use revised parts to avoid this?

oldmots

I just changed the O-rings on the cam sensors and magnets. I saw no indication of leakage when I pulled them out. Mine is a 2011. By the way, the magnet O-rings were $10 each...pricey O-rings.

Siegmann

The o-rings are not the problem, rather the sensors and magnets themselves leak oil internally through to the wiring connected to them. You mainly want to look in the connectors for oil.

Grant_J

Check your engine type and many other OEM details by putting your VIN in this site. https://www.datamb.com/ My 2016 Cabriolet is the M276. I believe you'll have the same engine.

Mr. Toad

Yes, I have the M276 as well.

syspklc53

Mr Toad
I was told my 2013 is not covered even though the symptoms are similar - found oil in CPS not Cam Solenoids (magnets) - ECU is backordered - ETA ???