decngb

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.

decngb

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.

konigstiger

OEM MB part # is 0041598103. Denso (spark plug by stock number): http://densoautoparts.com/find-my-pa...icle-selection Read attachment.

decngb

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.

Firestopper0383

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

mwmeci

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)

mwmeci

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.

konigstiger

You have engine 272, check PM.

mercerized

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