E-Class (W212) 2010 - 2016: E 350, E 550
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2014 W212 E550 Replacement Spark Plugs

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Old Jul 24, 2016 | 09:13 AM
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2014 E550
2014 W212 E550 Replacement Spark Plugs

I am in the process of replacing the spark plugs on my 2014 E550 Sedan. My replacement plugs are Denso 3444, but the diameter of the insulator is about 1.5mm smaller than the OE plugs. Has anyone ever replaced plugs and had the plug wires not friction-fit against the plug insulators?

I notice Autohauz specifies the Bosch ZR6SII3320 as an OE replacement, but says these plugs must be indexed. Those plugs aren't available locally (except perhaps at a MB dealer) and I've never indexed plugs. Also, the shop manual says nothing about indexing plugs. If I can use the Denso 3444 plugs, do I need to worry about indexing them as well?

For anyone who happens across this thread, note that the original plugs in this engine need a 12-point socket. Many spark plug wrenches are 6-point sockets, so they won't fit.
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Old Jul 24, 2016 | 04:47 PM
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I went ahead and installed the Denso 3444 plugs. They seem to work fine. I did send a message to Denso about the lack of friction between the insulator and plug wire. We'll see what they say about it.
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Old Jul 24, 2016 | 05:42 PM
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OEM MB part # is 0041598103. Denso (spark plug by stock number): http://densoautoparts.com/find-my-pa...icle-selection Read attachment.
Attached Thumbnails 2014 W212 E550 Replacement Spark Plugs-capture.jpg  
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File Type: pdf
Replace spark plugs.pdf (296.9 KB, 585 views)
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Old Jul 24, 2016 | 09:52 PM
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That Denso link shows the same plugs I installed. I'm a bit worried about the indexing, even though I torqued them down properly. I'll probably go back in and manually index & torque.
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Old Jul 25, 2016 | 08:08 AM
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Konigstiger, Dan you never cease to amaze me, and I'm sure many others, with your vast knowledge and ability to produce helpful documents for us.

Than you so much for being a part of our forum and so willing to assist us with great technical details about our cars.
Rich
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Old Jul 25, 2016 | 08:50 AM
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E350 4matic
Pardon my ignorance. Does my 2011 E350 4matic have the W212 engine?
I had a local mechanic replace my plugs recently and I don't know if he was aware of the indexing issue. I see the thread is about the E550. Does my E350 have to have the plugs indexed?
Thanks
P.S.
I noticed this in the link: With direct injection system for engines 157, 276, 278 (for example)

Last edited by mwmeci; Jul 25, 2016 at 08:53 AM.
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Old Jul 25, 2016 | 10:11 AM
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E350 4matic
Update. My mechanic talked to the tech people at NGK and they said the plugs he put in my car have the same thread length and specs as the original.
Part number NGK93911
Phew!
My mechanic is pretty sure he torqued them but is going to re-torque just to be sure.
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Old Jul 25, 2016 | 11:48 AM
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Originally Posted by mwmeci
I noticed this in the link: With direct injection system for engines 157, 276, 278
You have engine 272, check PM.
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Originally Posted by konigstiger
OEM MB part # is 0041598103. Denso (spark plug by stock number): http://densoautoparts.com/find-my-pa...icle-selection Read attachment.
Hi konigstiger,
Thank you for the pdf attachments.
It appears that my 2013 E350 4matic (engine 276), requires indexing.
Planning to use a Bosch OEM replacment plug,
Does that mean that I have to mark the electrode on my socket extension and tighten or loosen after torquing in order to get the indexing correct? Thanks
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