Hey guys,
After watching multiple videos, reading different PDF's and reading forums, I have decided to save some $$$ and do the spark plug replacement myself (Dealer wanted $750 and Indy $300).
I used BOSCH ZR 6 SII 3320, a quality dial torque wrench, thin wall 14mm socket and dielectric grease. HOWEVER I did make a s***** mistake and put a small amount of anti-seize on the new plugs thread (maybe half or even quarter of what you would usually put, and not even on the whole thread, just on half of it, if that) as it was a bit tough getting the old plugs out. Only after finishing the job, did I realize that the anti-seize I put may have effected the 23nm strict torque you are supposed to torque these plugs at. Feel so stupid I even tought about adding the anti-seize.

With that said the car runs and idles smooth, no check engine and no weird noises. If something, I can feel that it only runs smoother than it did in the before, and idles much more quieter than before. I ran the Torque app using the OBD port, and all the readings seems to be well, no errors or any alerts.

So basically I need your help on answering the following questions I have, please:
1) Do you think that the small amount of anti-seize I have added may have affected the torque to the point that the electrode position is not withing the 45 degrees of either side of the injector center, per requirements?
2) If so, should I take the new spark plugs out and clean the anti-seize off them?
3) If I take the plugs out, do I need to replace them altogether with new ones (they seem to have a crunch gasket), or can I use the same ones?
4) Should I just let it be and enjoy the car. Again, it runs and idles smoother than before with no worrying noises or feeling a lack of power.

I may be over panicking here, however I do feel threatened by the attached pdf file, Mercedes put together. Although I am not using the NKG plugs they mention there, but identical plugs to the original ones, and also this may as well be a scare tactic for people like me to get scared and go the the $tealership. Also, I have seen multiple people on this forum use anti-seize when they changed the spark plugs on their engines, without any issues (none with the M276 I think).

Appreciate any advice I can get here. Thanks!

 

Well after reading that and if they bothered writing about indexing the spark plugs, I would take them out, clean them and re torque them just for good measures. Indexing spark plugs seems important on these direct injection engines and the anti seize can also mess with the grounding of the spark plug.

 

Thanks for the advice @ltwargssf, I was thinking about doing that (although taking changing these plugs is a pain due to lack of clearance in the back). I think I saw somewhere that it said that these plugs can only be used (screwed in) once, as they have a crunch gasket on them. I am adding a picture of the plug, old vs. new which I took before placing the new one in. Is that true? And does that mean that I would need to buy those expensive plugs again? Or can I still reuse the new ones which are in there now?




Also, I ran the torque app this morning for my 35 min drive to work, and everything seemed OK again, with only one potential cylinder misfire trough he whole trip (which I think is normal for any engine). Attaching the results also.



Screenshot #1


Screenshot #2


Screenshot #3


Screenshot #4

Thank you!

 

No you can reuse the crush washers without issues, honestly if you barely put any anti seize I wouldn't worry about it.

 

Thanks @ltwargssf! Just to rest assured, I will mark the top of the socket with a line, and take one or two of the spark plugs out which are easy to take out (Without removing the ECU again). This way I can confirm that the line aligns with the open side of the spark plugs electrode. If it does, this would mean that the spark plug is facing upwards, towards the fuel injector, like it is supposed to be.

Now that I know that I can reuse the crush washers and that I can also use the same mark on the socket when placing in the spark plug. Hopefully, this will give me the right indication. Of course, while I have that one or two spark plugs out, I will make sure to clean the anti-seize on them and carefully off the engine thread itself.

Will keep you posted, thank again for all the help

 

It's not as serious as MB makes it out to be. We've done what you say, mark the socket and install them watching where the electrode lands, and if they are under or over torqued, or have anti-seize or not, makes such a small angle difference, it won't matter.

 

True, its the first time I hear a manufacture actually indexing spark plugs. I always did mine for extra performance and efficiency ( Using the marked socket way) but I guess direct injection cars are more sensitive and need a more precise spark to match the more precise fuel delivery. On a port injection engine it does't really make a difference since the air and fuel is just a free for all as it comes out of the intake manifold.

 

Thanks @ItalianJoe1! this is very helpful knowing that someone checked these torques. I was assuming at first that in the article they are referring more to using the right spark plugs (same length, thread and such), as they compared the MB original to the NKG plugs, which are completely different size.

So do you also think like @ltwargssf that I have nothing to worry about, and should just let it be as it is, or should I still go ahead and redo the plugs with marking a line on the socket this time?

Thanks again!

 

I wouldn't worry about it. If you put the right plugs in there, you will be fine.

 

Fascinating, first I've heard of indexing spark plug electrodes!

 

Alright, here is the update after I re-did 3 of the spark plugs which are easy to get to, without the need of removing the ECU (one side of the engine). That convinced me that there is no difference between using anti-seize in the quantity I did, or in reusing the crush washer. Pictures are worth 1000 words so here we go:


Spark plug after taking it out. I added the line as it was hard to see the one I drew on the socket.



All the anti-seize was pushed to the bottom, so did not seem to be any on the thread anyway.



The line when the plug was back in, torqued to 23nm.

So as you can see, there are maybe 15-20 degrees of the 0, which should be within the 45 degrees altogether as specified by MB in the article. But nowhere close to the 90 degrees of as with the NKG plug. Actually, it kind of sits right in the angle in which the MB original plug sits in the article.


From the Article: Below shows the indexing of the MB plug and the NGK plug when torqued at 23 Nm. Note: For our direct injection engines, the indexing is up to 45 degrees of either side of the injector center.

To conclude what I was able to find from this, it seems that as long as you use the right spark plugs and not the NKG MB mention in the article, and you torque it to the spec, this should be straightforward without any issues.

Thanks again for your help @ltwargssf and @ItalianJoe1! You seem to be true experts in this field

Thanks again, and let me know if there are any questions I can help answer.