Thanks for this great post. I started to get a misfire code (which has happened quite a few times over the years) and I thought 'Oh no, not again.... another $400 to MB!'. I have a repair manual & it suggested a problem with the ignition coil (which I have already had 2 replaced by the dealer) and/or spark plugs. But for some reason it wouldn't give any details on how to get to or remove the plugs! Thank you for your step by step post with pics. Cost me <$20 to repair (and a couple hours time) and I am sure saved me hundreds!

Thank you!

 

Nice post and pics; I think, for such simple jobs, DIY it's better , so we are sure what is really done to our beloved car......thank you!
In addition, I can say my mechanic told me to use some graphite powder as anti-seize, it
does'nt dry with heat, and is hightly dielectric also.
Graphite powder is available in locksmith shops for little money.

 

Just did this on my gfs car and there was oil all over the plug that came out of the number 1 ? Cylinder. The front one. The others were fine minus normal wear. I've tried searching the forums but I'm such a noob I don't know what I'm looking for. Lol. Any help would he appreciated!

 

Keep searching, this is a known problem with a gasket. I wish I could help with search terms, yet I know I've seen this issue before and probably even a DIY to replace the gasket.

 

Another trick since our cars seem to accumulate dirt in the spark plug holes and you definitely don't want this going down into the cylinder.

Take a long sharp object and loosen as much of the dirt as possible, then use compressed air top blow it all out. I loosen the spark plugs a bit and then hit it with compressed air again to ensure I got all the dirt out.

If you don't have an air compressor, the compressed air cans used for cleaning electronics work really well.

 

Thanks guys. I've been searching fora few hours now. I only have my phone so it makes it harder. I'll keep looking!!!

 

Great DIY post. Just changed the plugs on my 2004 C230 Coupe with 85,000 miles. Highway mileage gave me a clue that they needed changing. Bought car a year and a half ago and was getting consistent 30-34 mpg on the highway. Went to Florida last week and could only pull down 29 mpg. Old plugs were gapped at 041" and the ground had eroded into a V shape. I changed the air filter about a 1000 miles ago. The only things that I 've done to this car were 2 oil/filter changes and the dealer did the supercharger hose and the goodwilled the cam solenoids and associated hardware. Before purchasing the car the dealer had put in a new battery, changed front suspension bushings, and did the fix on the transmission connector. It looked like the previous owner had installed Koni struts and shocks. I also installed a Comand Navigation and recently found some AMG sway bars and 7 spoke 8-1/2" wheels for the rear of the car when I change tires. All in all this is probably the best Mercedes I've owned and I've had em all.

 

Great DIY. Quick question; It was said in the first post that it is recomended to change the spark plugs every 5 years or 80,000 miles. My car is a 05 so it is about 7 years old but only has 65k on it. Should I wait till 80k to change them or do them now? Thanks

 

Peydidy,

If your 05 requires same changing interval as my 03, then I would do it. It's simple and not much money and time.

 

Look I know this is an old post... I've been searching this site forever but have never posted... So I got a weird deal on my 2003 C230 Coupe that I came across today.

I went to change the plugs etc. I am not a newbie at cars but my last couple Mercedes' are constantly challenging me. lol.

So I buy NGK Iridium Plugs... The ones for the 1.8L... Right? So I pull my old plugs out and check them against each other like my dad always taught me to do, and noticed instantly the old plugs were "FR6" plugs and not the FR7's as this post shows and not the FR7's the auto parts store sold me... My old plugs were way way shorter than the new ones that the store assured me were the correct ones.

So I put it all back together and went back to the store. They again assured me I had the right ones.

I looked at a set for a 2002 2.3l and sure enough... The ones in my 1.8l 2003 were for a 2002 2.3l!!!! Needless to say I was scared to out longer plugs in my Mercedes.

Low and behold... Did the job and all seems good. I rolled it in 6 gear to roll the motor over a bit to be sure there was no interference.

How crazy is it that I've been driving this Benz around for 6 months with short plugs for a 2.3l???

The reason for the plug change was occasionally I get a "rough" idle... Once I let the clutch out and start going it generally goes away. I'm hopin this issue was the root cause.

I also cleaned the MAF sensor..

Thanks for all the help! You guys are the best.

 

I just did this repair about 30 minutes after finding this post. It cost me alittle more for the spark plugs and the plastic sleeves that go over the coils since I bought them from the dealer. I'm currently stationed in Germany and my service rep. recommended changing out the coil sleeves. Good thing he did because all four of mine were in bad shape. I had to follow the advice of poster "C230 Sport Coup" on gradually loosening the spark plugs. I remembered that 3-4 years ago I picked up my car from an independent service shop and I found that water was all over the engine to include under the engine cover. I used an air compressor to get all the water out but I had no idea of the manner in which the spark plugs sit on top inside those tubes. Well as it turns out those acted like small pools to the water because I found out today the damage caused. All four plugs were rusted sealed and all four coil covers were coated in brown. Took some work cleaning it all up but I'm so pleased with the performance. Maybe...just maybe that may have played a part in the rough idle.

So...without a torque wrench....How tight should the spark plugs be? Cranked down tight or just slightly above hand tight......

 

I just changed my plugs today at 118k .. .70k since the last change. Pics of the old plugs are attached to this post.

Great DIY -- the pics make it much easier! I have a few notes:

* I believe torque should be 25 nm or 18.5 ft-lbs. I've checked with a few sources on this. There is a youtube video that also claims 18nm, but I think that is wrong. The difference between 18nm and 25nm is only about 1/16 of a turn, so it's probably not a huge deal if you do it one way vs the other.

* My old plugs came out very "gooey", like I was turning them in molasses, and there was a lot of black residue in the spark plug wells. Upon further inspection it looks like the indy who did the first plug change use a lot of anti-seize on the threads and it squeezed out the top of the hole and got under the crush washer. When I put the new plugs on I applied it pretty sparingly, lightly coating all except for the top and bootm few threads, and wiped it down to make sure there was no excess.

* I will note -- it is laughable how little anti-seize and dialectric grease I used. I bought those little Permatex packets that hang on the racks at the checkout counter ... $1.29 each packet. I probably used no more than 1/20th of what's in each packet.

* The old plugs were not in bad shape, and by shining a shop light through the spark plug hole I could see that the top of the pistons were pretty clean ... so I guess the Chevron gas with Techron that I use religiously is doing it's thing

* I had a hard time understanding how to "extend" the coil packs to 124mm. Turns out I don't think mine were extendable, and once I measured them properly I found that they were already set at 124mm. Are these not adjustable then?

I haven't driven the car too much yet but I'm glad to have yet another maintenance item out of the way for another several years.