Where is this Purge Line???
 

I currently have the same issue. Hoping someone in MBworld can answer this.

Was it clear where the broken hose you replaced was connected ? Any chance the new one was incorrectly connected ?

Update: I spent a few hours on Sunday poking around the engine to check hoses and try to pinpoint the source of the "puttering". Didn't find any damaged or loose hose, but the "puttering" noise turned out to be coming from the engine itself. After some research, I found this video on youtube that sounds exactly like the noise. ( ) My engine progressively worsened from a puttering to a full on rattle at startup in the last few weeks. From what I've read, the sound can be related to the camshaft adjusters which apparently is a known issue with the M271 engine. So at this point, I've gone down the rabbit hole of camshaft adjusters, timing chain, etc as the potential cause of the noise. I'm struggling to see how a simple purge line could be in anyway related to it. There was a theory in another forum post that said engine rattle could be caused by fuel getting into the engine oil. Perhaps there's a connection to this "purge line" and allowing that to happen.

Update 2: I found the "purge line". I ordered the part number that the dealer reference on their findings report (271-018-02-00) and it arrived on Weds. This was a big help. I took a good look at it and went hunting in my engine compartment. It turns out that this part is the second hose section after the evap system purge valve. It attaches to a 90° rubber connector (upstream), then wraps underneath the intake manifold and out of sight. It has a check valve at the other end (downstream) which plugs into the engine block and then another connection point for another hose to attach to the body of the check valve. Looking at the photos below should help if my description sucks.

I tried for a good hour to swap the new one in from the top side, but I didn't get anywhere. Since I couldn't see the check valve side, I was basically working by feel, and wasn't able to get it unscrewed. I think it will probably be easier to work from underneath the car with the splash shields removed. I have an appointment for a lift bay at a DIY garage tomorrow morning. I'm going to try and swap it out from underneath the car, do an oil change, and pray that it helps eliminate the rattle on startup.

Would love some pointers for anyone who's done it before. Not much turned up on youtube and previous posts about this particular part or swapping it out.


https://cimg3.ibsrv.net/gimg/www.mbw...37e2052347.jpg
View from top showing mystery purge line from dealer service report.

https://cimg4.ibsrv.net/gimg/www.mbw...75930acd9b.jpg
Closeup of top of purge line

https://cimg2.ibsrv.net/gimg/www.mbw...a103184540.jpg
Picture from underside of manifold showing where it connects to. This is out of view from the top. I had to reach my iPhone down in there to take the picture.

https://cimg4.ibsrv.net/gimg/www.mbw...553b77e785.jpg
Here's the new part that came in. I'm holding it upside down from how its actually installed in the car.
https://cimg2.ibsrv.net/gimg/www.mbw...b5bcf22531.jpg
Check valve front
https://cimg3.ibsrv.net/gimg/www.mbw...5629c8bde4.jpg
Check valve back showing connection
https://cimg2.ibsrv.net/gimg/www.mbw...9da1d74304.jpg
Part number shown

I just worked on a 2012 C250 with the same issue. The vehicle kept throwing a P0441, but with no freeze-frame data available. The gas cap seal tested fine. At a glance, the FTP sensor responded normally during purge duty cycles. We replaced the Purge Solenoid assembly with a Genuine MB unit and the issue went away for a short period of time. Thanks to this thread, we became aware of a check valve in the purge line assembly.

The Purge Line Assembly is bolted to the underside of the intake manifold. Unfortunately, there is very little clearance between the bottom of the intake manifold and the A/C compressor; the purge line is bolted to the intake manifold using a T25 fastener. So, you have two options - a) remove the intake manifold assembly or b) remove the throttle body, drive belt and unbolt the a/c compressor (with the lines attached). I chose the latter; keep in mind that two of the a/c compressor's E12 bolts are best accessed thru the driver-side wheel well using a variety of wobble extensions.

I think the purpose of the check valve is to prevent boost pressure from going the other direction (i.e. back towards the fuel tank). I blew into the portion of the purge line that connects to the intake manifold, and the old one allowed air to go right out to the purge solenoid connection. The new one did not. So, I am fairly confident that the old purge line assembly on this car was bad.

Also, I checked for a ME update using our Autel's server (not sure how updated this is) and it appeared that this particular vehicle was already up-to-date.

Hope this helps.

https://cimg2.ibsrv.net/gimg/www.mbw...cbe4a1e832.jpg
Disassembly required to gain access.

https://cimg5.ibsrv.net/gimg/www.mbw...7440a5b529.jpg
No update was available.