M271 - oil in connectors? - Benzworld.org

taylor192 · 11-12-2007, 08:47 AM

I noticed a bit of oil in the O2 sensor connectors when I replaced them, yet didn't think much of it as it was only a small amount, cleaned them and installed.

My car has been needing < 1L of oil per 15K kms, nothing major, yet enough that I wanted to find the source.

Looked into other oil leaks on the W203 and saw the cam magnet sensors have leaked on the M111 causing oil to get into the harness.
I checked, and there's oil in the cam magnet sensors on my M271.

Luckily there no oil on the MAF sensor, or ECU connectors, so the problem might be isolated unlike the disaster it is on the M111 that ruins the ECU and requires the entire wire harness to need replacing.

Can someone do me a favor:
- pop the connectors off and look to see if there's oil on them.
- the magnets are circled in orange in this pic:

2002c230 · 11-12-2007, 09:04 AM

Quote:

Luckily there no oil on the MAF sensor, or ECU connectors, so the problem might be isolated unlike the disaster it is on the M111 that ruins the ECU and requires the entire wire harness to need replacing.

Can you go into more detail of the M111 problem, or link me to the thread(s) you found the information on? My 02' C230KSC had oil in the air piping, and on the MAF... Not sure where the ECU wiring harness is, so I haven't checked that.

Thanks,
Matt G.

taylor192 · 11-12-2007, 10:33 AM

Confirmed with the dealer - the cam magnet sensors are leaking on high mileage M271 engines.

Its a $500 part and 6hrs of labour to replace the engine harness.

The typical failures are the O2 sensors as the oil destroys the sending units.

So far this year:
$300 MAF
$250 for both O2 sensors

Now:
$100 cam magnet sensors
$500 engine harness
$250 possibly new O2 sensors since the CEL is back

taylor192 · 11-12-2007, 10:34 AM

Quote:

Originally Posted by 2002c230

Can you go into more detail of the M111 problem, or link me to the thread(s) you found the information on? My 02' C230KSC had oil in the air piping, and on the MAF... Not sure where the ECU wiring harness is, so I haven't checked that.

Thanks,
Matt G.

Search MBWorld, you'll find all the info there.

2002c230 · 11-12-2007, 12:23 PM

What to search for though? If you could provide a little information that would surely help. I would definitely appreciate it.

taylor192 · 11-12-2007, 02:21 PM

Quote:

Originally Posted by 2002c230

What to search for though? If you could provide a little information that would surely help. I would definitely appreciate it.

cam + magnet + oil

search in the W203 forum and read, come on, its really not that hard, took me 3 threads by searching for: oil + connector

**Buellwinkle** · 01-17-2008, 09:15 PM

This problem seems to happening on the M271 motor's (2003-2005 C230) at about 50K miles, just after the warranty expires. What happens is the cam sensors leak oil were the wire goes into the sensor, then the oil travels down to the O2 sensor and kills it. Before you get stuck with a big bill, if your car is still under warranty, pull the plastic cover off the engine and check the connectors as shown in the picture above for the slightest trace of oil and if there is, get it fixed under warranty. There's a TSB on it. If it's out of warranty, replace it before it gets worse.

If oil gets in the harness and damages the O2 sensors, not only do you have to replace the O2 sensor but that entire section of wiring harness, not cheap. Prevention is the key and even getting new sensors doesn't solve the problem, just pushes it out another 50K miles, hopefully.

Also, MB has a harness that is supposed to prevent the oil from getting in the rest of the harness (see pic below). This does not prevent the new cam sensors from leaking, just controls collateral damage.

SERVICEWRITER · 01-31-2008, 01:32 PM

I've searched too already anyone have the TSB # for this problem??

**Buellwinkle** · 02-01-2008, 10:27 AM

I can tell you but then you'll just be hungry for more information tomorrow. So I will teach you how to fish instead - ODI - Office of Defects Investigation

BTW, I'll give you a hint, it's for 2003 C230 (it hasn't been released to other years yet but if enough complain on that website it will be).

garik · 02-21-2008, 11:18 AM

i have 2005 240 and i had to take my car to dealer last week for leaks around valve cover. they ve replaced valve cover gasket on both sides (v6). and the car has only 38k miles. looks like there is lots of places where oil can leak... we just have to keep on checking on it.