OK my C230K peeps, this is for you. Just changed the plugs in my '05 and have pics for you to help you out should you want
to save about $350.00 on the job. More on that later. Disclaimer before I start: IF you are not at all mechanically inclined, don't do this. If you are, it's a piece of cake. I started by ordering the plugs from www.autopartswarehouse.com for $12.90 each, for a total of $51.60. No tax and no shipping on orders over fifty bucks. I had the plugs in three days in the mail.
You will need what I show in one of my pics. A 5/8 spark plug socket and ratchet and extension, a 1/4 inch ratchet with a 1/4 inch socket and some anti-sieze. DON'T do it without the anti-sieze. Good mechanics use this stuff on unlike metals to prevent problems. Only costs a few bucks for a tube. So now, I have about 55 bucks invested. The rest is all labor, and it took me about 35 minutes for the entire job.....that's stopping to take pictures for you and answer the phone once. OK. Here's what you do:
1) Remove the oil filler cap on the front of the top cover.
2) Pull each side of the top cover UP....you will see the four fasteners that hold it on in the photo.
It's a bit stubborn, but it will pop up and off eventually. Go slow and try not to break the little black plastic "posts".
3) You will see a small black plastic canister held on with a black clip. Undo it and slide that thing out of the way for now.
This will help you remove/install the third coil pack from the front as shown.
4) PUT THE OIL CAP BACK ON LOOSELY TO PREVENT DROPPING ANYTHING IN THE ENGINE!!! (PS...I didn't).
5) Starting on the first coil pack in the front, undo the black wire harness and move it out of the way.
6) Using a 1/4 inch socket on a ratchet, take the coil pack bolts out and CAREFULLY pry and wiggle at the same time the coil
pack upwards to remove it. The thing is snug on the top of the spark plug, which you can't see at this point, so a bit of
upward pressure is necessary to get it to come off, but it will. Pull up and set coil pack aside.

NOTE: Mercedes Benz has been kind enough to use a "reverse torx head bolt" to hold the coil packs down. You probably
don't have this socket on hand, but DONT PANIC. Just use a normal 1/4 inch socket and it will fit and do the job. Let's all
try to guess why they used this particular bolt head....uhhhh....yep.....you guessed it! But it isn't going to stop us. I'll tell you why they used this in a minute.....keep going.....

7) Using a spark plug socket (5/8 with the closed-cell foam inside) remove the plug, which is kinda deep in the head.
IF the wrench won't grip the plug tight enough, you won't be able to reach in there and pull it out. A magnet won't work.
Guess how I know. So, use something else to get the plug out if it slips off the foam in the socket. One of those claw-like
grabbers works or you could be inventive and use something else...just wanted to warn you now.

8) Put a SMALL amount of anti-sieze (you know, the one you DIDN'T buy!) on the plug threads. Don't overdo it. Tighten the
plug and place the coil pack back in place and wiggle it down until it fits on top of the new plug properly. When it's seated,
you will see the coil pack now flush where it bolts down. Tighten bolts, put black plastic wiring plug back on, and move on
to the next plug. REPEAT procedure. You're a pro now, so no problem.

HELPFUL TIP: On the third coil pack, you will see a small round plastic thingy in the way a bit. Simply unclip it with it's clip and move it out of the way for access. SEE PIC.

9) When all the plugs have been replaced, check all the wiring harnesses, etc. and put the little black canister back on it's clip, remove the oil cap you put back on to prevent dropping anything down there, and snap the cover back on WITHOUT THE OIL CAP ON PLEASE!!!....then, put the oil cap back on tightly and you're done.

DO NOT TRY TO GAP THESE PLUGS! They are Laser Iridium and you will screw them up trying to do so. They are made
that way.

NOW for the upside of your work: Mercedes just quoted me $405.00 to replace these four spark plugs.
YOU just spend less than an hour (hopefully) and saved about $350.00.
Mercedes wanted $25 for each plug and yes, THREE HUNDRED PLUS dollars for labor.
I'm guessing a good MB mechanic can do that job in 15-20 minutes max. I did it for the first time in 35 minutes.
Yes, I have lots of mechanical experience. Can you do it? YOU decide. I hope this helps my MB peeps. If I left
anything to the imagination, sorry. Oh, by the way, my car has 103,000 miles on it and this is what led me to do this.
Mercedes recommended changing them at 100K, so I did. You can see in the photo the conditon of the old plugs. The
electrodes are supposed to be "pointed" like that. That's the way they come. Report on gas mileage coming soon.

Hmmm....having trouble attaching the five pics I wanted to show you so I'll try it a different way.....sorry.

 

I'm having fits trying to post the five pics I took of the job. I've done this before when I did my fuel filter,
so I must be doing something wrong. I click on "upload photo", I see the choices, I click on one, then hit
"Choose" and then when I try to attach it or put it in the reply, I get a window that says DISK ERROR or
something. Very frustrating. What the heck am I doing wrong. [:@]

PS>>on the freeway tonight at 65mph steady driving, my car with the new plugs got 34.9 mpg.
It has never been that high ever before. Plugs really helped it. Money well spent, huh.

 

OK! Pics are now in my photo gallery......just search for "mrcoyote" and you will see them.
Hope this helps out somebody in the future.
Gas mileage is WAY up.