I searched for what seemed like forever and could find nothing on this. I could not even find how many plugs this engine had. Everything I found said 16 (2 per cyl) but I was looking at only 8 coils. So, I thought I'd document my plug change. When I was in for some service a while back, I was quoted $600 to change the plugs and I thought, "no, I think I'll wait on that one" since the car only had 65,000 miles on it but was 5 years old. Glad I did. It cost me $116 for plugs and 3 beers and about 1 and 1/2 hours taking my sweet time. So I hope you find this helpful.

1. Make sure the engine is cold or risk pulling threads out of the head.
2. Raise the hood to the complete vertical position by depressing the tab on the inside of the hinge on both sides of the hood.

3. Remove the front portion of the engine cover by pulling straight up on the middle portion. The font is a friction fit over rubber and the rear is held in with clips.

4. Remove the air filter housing. Using a flat bladed screwdriver push the retaining clip at the rear of the housing towards the firewall.

Remove the crankcase vent tube in the front left of the housing and then pull up on the front of the filter housing with both hands. The woven fabric tubes connecting the filter housing to the air ducts in the grill will come loose as you lift up. The rear portion of the filter housing has a round opening that fits over the intake opening. With the filter housing removed, place a shop rag over the intake manifold opening to prevent debris from entering the engine.
5. Note on this engine there are 8 coils over plugs.

BEER INTERMISSION

6. You will need to remove the connectors from the wiring harness to the coils. Note that you need to extend/pull the grey tab out about 1/8 of an inch to unlock the connector. Then, pressing down on the gray tab while pulling, disconnect the connector from the coil. Repeat for all 8 cylinders. The wiring harness keeps the connectors oriented so I did not need to mark the wires.
7.Using a Torx T-40, remove the two bolts holding the coils to the valve covers. Pull straight up on the coils to remove. I don't know if it makes a difference, but I kept all the coils arranged on the bench to make sure they went back on the same cylinder. It should look like this.
8 Now that you have the coils off, you should use compressed air to blow out each spark plug recess in the head to avoid having debris enter the engine.
9. Using a 5/8 spark plug socket, remove all the plugs. Inspect the bores of the spark plug recess again. On at least one, I had some debris that did not come out when I blew it with a compressor so I used the shop vac to remove it.
10. These are the old and new plugs.
71,204 miles and 6 years old.

Interesting to note the OEM plugs were NGK and I assumed they would be Bosch. I used Bosch platinum iridium YR7MPP33

BEER INTERMISSION

11. Install the new plugs taking care to lightly coat the threads with anti-seize compound without getting any on the electrode. It only takes a light coat, so don't overdo it. Torque to 23Nm. Don't skimp. Use a torque wrench.
12. Reinstall the coils putting them carefully over the plugs and then reinstall the two bolts using the T-40 Torx. Torque to 9Nm.
13. Re-attach the coil wires and remember to push that grey tab back in until it clicks.
14. Reinstall the air filter housing being careful to remember to remove the shop rag from the intake opening. Take your time. Start by placing the round opening of the filter housing over the opening to the intake manifold first. Aligning the woven fabric tubes and the clips over the rubber posts will take a few minutes to get right. Don't forget to pull the clip at the rear of the housing back towards the front of the engine.
15. Install the front engine cover placing the rear clips in the slots on the front of the filter housing and then press down on the front to engage the clips over the rubber post.
16. Lower hood
17. Test engine and admire the $500 you saved.

BEER INTERMISSION

 

How often does spark plugs need to be changed on CLS?

 

According to MB, every 91,000 miles or 5 years. Most people that I've spoken with don't like to leave them in the head for that long as it increases the chance for pulling the threads out of the head when removed. Performance degrades over time/mileage, so as a matter of course in all the ones I've owned, I replace them about every 70-75k miles regardless of age. Remember a lot of the service intervals are set because people want a hassle free experience with a new car. They are NOT designed for those of us who want to keep a car for more than 100K miles. If you plan on flipping the car for something else, stick with the factory recommended service intervals. If you want to keep it, then be more proactive on everything. Brake flush, transmission fluid change, plugs, etc.

 

oem plugs r BOsch......some body must have changed the plugs before n not from dealer....

 

Nope. Bought it new. Plugs that came out of it were NGK and had a mercedes emblem printed right on the plug.

OEMs source from multiple vendors for things all the time. This must have been one of those items they sourced from multiple vendors.
You can see it clearly in the photos.

 

I need to do this on my CLS55. So, what's the verdict, 8 or 16 plugs? I only see one per cylinder in your pictures...maybe the AMG has 2 per?

 

Great post! Thanks for the detailed pictures and torque values.

 

8 only on this engine. I can't speak for the AMG63, as it is a completely different engine.

Oops. Just saw you're in the 55AMG. Its easy enough to just pull the air cleaner and look on the top of the heads to see if you have 8 or 16. As you can see from the pics, the coils are right on top.

 

Great write up !

 

You're welcome! I have benefitted over the years from many others who have taken the time and it was high time that I paid it forward.

 

Thanks for sharing. Hope you enjoyed the beer intermissions.

 

Thanks for the diy I just did mines today. Torqued everything down to spec and saved myself some money. It was quite easy. Ignition coils just like my 2000 bmw 740il. I bought the spark plugs from the dealer like a big dummy tho.

 

you bet! Glad it helped.

 

While taking out the housing the metal clip located at the end of the housing jumped out and I can not find the exact location to place it back. Can you please show me where is it must be placed?

Thank you!