All, So I have to ask, is it mandatory to remove the engine to replace the harness? Peter

 

For my 4matic E550, that's what the dealership did - the whole harness replacement requires access all around the engine, like even to the "should be disconnected" oil pressure reducer solenoid (my replacement harness plug was dry when I permanently disconnected that POS bad idea from MB). Mine was leaking in at the VVT plugs - think I might buy the extenders (just in case the new harness might leak). I want to keep this wonderful car for a long. long. time...

 

D_Dan, it's funny you point out VVT as the source of oil-in-harness.
​​​​​​Replacing the harness without addressing the root-cause maybe an endless repair gig.


Extreme heat soaks fries engine plastics.

With better oiling for pistons heat removal and sacrificial pigtails this nightmare has a fair chance to be cancelled.

 

I have to be curious who is recommending to replace the entire harness, for what problems, and who is paying?

I found oil from the cam sensors all the way at the ECU when I bought my ML63. No errors. I replaced the sensors, cleaned out oil from both ends with contact cleaner, and all remains well over 2 years later. Unless a warranty is paying, I'd definitely try cleaning things before jumping to pull the engine and replace the entire harness, but that's probably what dealer service is telling you because it's the only way they will guarantee the work.

 

The reason that I didn't/haven't done the pig tail extenders is that I understood the new sensors (or was it the harness?) had been improved to not allow oil through. You are saying this is not the case? Where are folks getting these pig tails for the VVT plug ends? Thanks!

 

yes, exactly! The newer superseded cam sensors do not prevent oil from leaking into harness.

You can get disposable pigtails for 3-Wires CPS and 2-Wires for electromagnets.

NOTE: the pigtails don't prevent "oil in harness" either!
They only act as disposable harness.

So our best interest is to prevent oil from leaking out...
-- New plastic sensor/magnet collection
-- Better oiling to prevent "extreme engine heat"
-- Fresh pigtails

Then you'll also get more stable performance from better positioning of VVT Gears with favorable oil pressure.

 

Thanks! I found aftermarket pigtail sets on ebay and ordered a set . The whole harness and sensor replacement was done 7K miles ago - I do need to check and see if all the VVT sensors were replaced or just the cam sensors...

 

I've replaced the 8 sensors that were leaking on my 2 cars in the past couple of years. I check them each oil change and the new ones are not leaking. No need for the extensions, but FCP Euro does sell a kit with the 4 cam sensors and extensions. I bought my sensors from FCP so if they do leak I'll just get their lifetime warranty replacement.

 

usually it's the cam position sensors that get toasted (3-wires).

The VVT gear actuator coils are exposed to less heat on the timing gear cover, air cooled a bit (2-wires).

All 8x pigtails is best practice.

 

Thanks for all your advice! You help way more people than you ever hear from, so thanks for them as well... Checked my dealership paperwork and Yes, they only replaced the 4 Cam Position Sensors. So one more thing soon to not worry about by doing all 8 pigtails!

 

So apologies if this was covered earlier in the thread but I'm trying to figure out why oil would cause problems for the wiring, in my day job we run all sorts of signals and power through oil filled volumes without issue. I have seen oil cause insulation to crack but the pigtail solution wouldn't work if that was the case. BTW I also think Mercedes should be ashamed of themselves for not being able to seal these sensors. Is it that the oil may have trace amounts of burned fuel?

Just wondering...

Peter

 

Peter, thank you for chiming in. You're right it is a bit strange at first but it's so popular that we stopped questioning this being an issue. It has been produced for a sweet long time.

We don't exactly know how the oil-in-harness messes up the Bosch ECU. It is built without solderless issues. It has standard heat issue with leaky caps.

As you point out: oil is known to be more electrically insulting than shorting.
The TCU is built inside the oily gearbox connected to electric solenoid electro valves - It works real well.

Usually oil-in-harness invites itself down into exhaust lambda circuits... in the end the giveaways are misfirings.

Fearing the huge repair tab ppl have developed counter measures with pigtails and recently controlled heatsoak temps.

Every M276/8 is guaranteed to leak... check your CPS connectors for status.


How can we go a step beyond where we're at??
What do you think?

We are short of couple details here... spray-cleaning is not great but at least helps. Perhaps its just the ECU connector with spring loaded females side...

 

PWe find some MBWorld Mod willing to sticky this stuff at the top of all forums it might relate to! Unplug the dang oil pressure reducer solenoid and inspect/install the sensor jumpers and I bet there is a thread here about getting the alternator to run all the time, as well as other "fixes" I've missed... Just so we can make the newer MBs as reliable as possible to the older ones...

 

Dan, you guessed right!
There is a thread about disabling the amazin' "Battery YOYO": pull ALT LIN connector

This is how Master Surya and I started diving together in the depth of WIS design docs, taking apart modules looking for answers.

And boy did we get answers, more than we bargained for...

We found out how everythings carefully stacked up to deliver the legendary Mercedes ownership.

++++ A few tweaks...
A couple details in each systems can be reworked to unlock *normal* W212 performance better than new.

At 50kMi I effectively canceled the following built-in factory defects:

• laggy weak throttle
• clunky tranny shifts
• extreme heatsoaks
• springy brakes (floating TRW calipers)
• bouncy suspensions
• wandering steering
• moody keyfob
• battery drains parked + driving
• smelly coolant leaks
• vaporized oil leaks
• squeaky wiper's angle
• sticky parking brake coil
• PITA seats literally!
• ESP disabled IC message
• ...

It's all simple once you're stop chasing your tail clueless.

My favorite feature in this car is the 722.9 transmission: very honestly smart.

 

So I followed your footer link, and excuse me if I only watched the original 3 Star Wars, but help me Obi Won - What/Where Is the ALT LIN connector (Assume on the alt?) - Boy I wish these tricks and tips were in a place most human fools that love their cars could find them....

On edit: nevermind - I saw a yoyo thread and don't think that is happening (anymore) to our car. We went through batteries regularly, but when the MB dealership forgot to install the main grounds correctly, I think a tech went through most every possible ground issue and they verified our Alt was putting out 14.8V. Hmmmm... trust the untrustworthy dealership, or test and verify.... Might have to go with the latter here! Thanks again!

 

Yes ALT LIN unplugged to let Valeo smart regulator perform flawless voltage regulation thereby disabling drive-by-draining 90A battery killer.


I let Master Surya @S-Prihadi describe how his chassis benefits from *normal* voltage for awesome Air-Con with the WTF-Heater disabled

I stuck with LIN chaos as motivation to research a full fix. I can say it involves the whole CGW bottleneck designed arround solderless pressed-pins modules.
I believe I sport a working 12.6V_14.9V stock without drain below 11.x

Most of this enabled by team-work empowered by #1: MS!

 

Phew, all sorts of theories here. Working on the theory from above that the harness transports oil to sensors that cannot tolerate oil is there evidence that replacing the sensor provides a temporary solution? Peter

 

I do not have good hands on this topic.

My original CPS have started to leak out around 50kMi when I did the sparkplugs. I then installed pigtails... this may give me a reason to open up my Bosch ECU. So far so good 🤞

The main oil path is CPS --> ECU /(> lambda).

Hot oil travels by capilarity along the stranded copper inside the plastic wire protection.

CPS 3-Wires go to 3 junctions meet more friends.
You can follow schematic branches and guess where the oily junctions are.

In addition the "oil-pump solenoid" 2-pins connector is also enabled with this oil leak.

The plastic molding splits away from the metallic through pins. Oil is delivered right into female side and onto next junction it goes.

My CPS being wet, I can confirm with some degree of confidence, oil does not disturb low-voltage pin connections... perhaps it does on sparkplug COP or piezo-injectors??

From what I have seen of ECU, I don't think it uses the solderless pressed pins... so I don't know how the "OIH misfires" is generated...


Let's try to put this one to bed collectively.

++++ M276 ECU ok...
no loose pins, they are normally soldered .

MED17 Confirmed ok

thia ECU fries its undersized capacitor that burns PCB - This suggest power glitches are involved - Fix "Main GND Strap" may prevent that!

 

You should read the thread. These aren't "theories", they are reports of an actual issue that has real problems that are caused by it. Similar threads to this one exist across a number of sub-forums here and on other MB enthusiast sites... Replacing the sensors is part of a solution and can be done proactively, but a far less expensive one is to add on the pigtail extensions to both the Cam Sensors and Magnets.

 

CaliBenzDriver, Thank you for your reply, I'm left scratching my head regarding MB's response. Why would they make a costly repair of replacing the harness as opposed to adding some sort of inline protection to key components? One theory is that MB cannot protect the ECU and feel that if oil is in the harness it's just a matter of time before it gets to the ECU (which frankly should be able to tolerate oil). Also there are reports of oil affecting coil packs, all the ones I've seen look potted so how does oil affect these. Heck come to think of it I add silicon grease to all sorts of connectors. Clearly there are things going on that I don't understand, hence the theories, nothing new.

Peter

 

yes Peter, nothing new besides silicone grease in connector is a bit of a divisive subject around here...

I used to think like you that grease would protect oxidation
then I crossed to the other side
thinking I don't want to insert insulation in my connections.

So yeah, let's get test results.
How about pack your ECU connectors with silicone and report outcome at 500Mi


reliably soldered pins

this maybe viable - At least we know ECU 2x connectors are honestly soldered onto PCB.

 

I use silicon grease mainly for mechanical purposes, to lubricate the connectors so they're easier to take apart next time. Packing the connector volume seems risky particularly if the connector is sealed. If the connection is mechanically too weak to displace the grease you'd like get intermittent connections with shock/vibration. I have seen the grease chemically react with silicon o-rings but the o-rings were defective. I apply sparingly to spark plugs to avoid the rubber boots sticking.

 

Peter you're right, lubing the wide outer seal on connectors make them ZIF easy to work with.
Somehow I still keep silicone off my electrical connections.

Have a look at this AMG thread ... so far it looks like textbook OIH case.
We'll see what testing shows... hopefully we get clues to draw conclusion.

 

You guys might want to try this directly on electrical contacts - it actually improves conductivity

 

Dan, I'd stay a bit on the conservative side with the connector lube/protection... as in use it on light bulbs but not VIP $$$$ modules pins/connectors.

Personally I lubed the rubber contacts (dielectric clean silicone) in :

• Driver door main window switches
• steering wheel paddles + buttons

​​​​​​but none of the many module connector pins I visited - I could always be wrong