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M271 - oil in connectors?

183K views 170 replies 72 participants last post by  narutokaya 
#1 ·
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:
 
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#2 ·
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.
 
#3 ·
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
 
#5 ·
What to search for though? If you could provide a little information that would surely help. I would definitely appreciate it.
 
#7 ·
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.

 
#10 ·
oil leaks

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.
 
#13 ·
Hi all,

I've been lurking for a while and really appreciate the information available here on the boards.

I have a 2004.5 C230K SS it just turned 79K miles. I bought it used 5 months ago with 63K miles on it. I just took it in for the PCV service campaign last week. I purchased the cam sensor starter leads at that time. I had check my cam sensors 30 day ago and they were fine. But when I went to install the "adapters" I noticed one started leaking. So I'm ordering a set right now. My question is do the new sensors come with new o-rings or do these need to be ordered separately? There is also a plug listed do I need to order that too?

Any help would be greatly appreciated.

Thanks!
 
#20 ·
Hey man we see this all the time at the dealership we look at it as gravy considering you can replace the wiring harness in about 2-3 hrs make sure you don't have any oil at your M.E. control module either I have had that one bite me before anyway the source as you probably know is the cam adjuster magnets Mercedes has come up with a updated part number as for any bulletins I dont think there is any for the 271 just the 111 but hopefully all goes well let me know if I can be any more help
 
#38 ·
Can you please provide the part numbers for the engine harness and the updated cam adjuster magnets. I've put the starter cables in line with the adjuster magnest but the rest of the harness has so much oil in it that every week or two I have to clean the Oxy Sensor and Control Module connectors to get rid of the Check Engine light.
 
#28 · (Edited)
a little preventive maintenance

I just did this work as I found a little drop of oil in each of the cam magnet connectors on my 2005 C230K with 70K miles on it. You'll need to remove the little cover on the front of the engine. No tools needed, just pop it loose from the rubber bushings. After that, a small external torx socket is required. As mentioned, you'll need:

2x - 271 051 00 32 - Expansion Plugs (called "cover" on mine)
2x - 010 997 23 48 - Seal Rings (just an o-ring)
2x - 271-150-27-33 - Isolating wire (called "starter line" on mine)
2x - 271-051-01-77 - Cam magnet sensor (just called "magnet" on mine)
2x - nylon zip ties (also called tie-wraps) get them anywhere

Also mentioned was autopartspeople.com which I found to have pretty decent prices on factory parts. The first part, the expansion plug (called "cover" on my part bag label) is the rubber plug that goes in the center of the magnet. I installed the new magnets without first putting the new plugs in. Don't do that! It's a little more difficult since you might drop the plugs down into the void. The new plugs did not look like the old plug used on the original part, which confused me for a second. The seal ring is simply the o-ring that goes between the magnet and front of the head. The isolating wire is a short piece of harness that has a male connector on one end and female on the other. Put it between the magnet and existing harness connector to stop future oil from migrating down the wires. You'll need a "zip tie" or "tie-wrap" to secure the new bigger bunch of wire/connector to the two brackets that support the little cover for the front of the engine. To save yourself some money, you might consider leaving the magnets alone, since the new isolating wire will keep oil from damaging the other stuff. You may get a worsening oil leak but you can replace the magnets then. Easy job, less than an hour, have fun! (...and thanks to the previous posters for all your help. made my job so easy)
 
#76 ·
...The first part, the expansion plug (called "cover" on my part bag label) is the rubber plug that goes in the center of the magnet. I installed the new magnets without first putting the new plugs in. Don't do that! It's a little more difficult since you might drop the plugs down into the void. The new plugs did not look like the old plug used on the original part, which confused me for a second...
I when to the dealer for the vacuum hose replacement campaign and sure enough the service manager called inform me that I have oil in the cam magnet connectors. He wanted $400 to change them out. I rightfully declined and thinking I can do it myself after reading all the posts on here. So I bought all the parts from the dealership ready to change out my cam magnets.

2x - 271-051-00-32-05 - Expansion Plugs
2x - 010-997-23-48 - Seal Rings
2x - 271-150-27-33-05 - Isolating wire
2x - 271-051-01-77-05 - Cam magnet adjuster

My question is with the Expansion plug/cover, which ends will go into the magnet (round or flat)?
 
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