Jun 10, 2015, 12:58 PM
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C300 spark plug change DYI
Thread Starter
Junior Member
Joined: Jan 2014
Posts: 34
Likes: 0
From: Indiana
W212 E350 4 Matic 2011
C300 spark plug change DYI
After looking at various videos on you tube (none of the W204 specific) and checking out what people had said I decided to change my spark plugs today:
Bought original MB spark plugs. Online from MB dealer got all 6 for about 84 USD delivered to home.
You can buy the NGKs or Bosch for 6-9 bucks a piece.
The MSRP on the plugs is 15 USD but I have seen them up to 25 on ebay.
picture 1
You will need a T30, Ratchet and a 6 inch extension.
It would be good to have a torque wrench so you can tighten your plugs to specs (more than I would have with a "naked" hand)
15-18 lb-ft
Take our the front cover of the engine, then the air cover with filters after removing both air ducts
picture 2
picture 3
picture 4
picture5
Then proceed with unscrewing the 2 torx bolts that hold the coil onto the plug
picture 6
picture7
Remove the spark plug: it needs a good effort
picture 8
Comparison of the 2 plugs, new and old
picture 9
picture 10
picture 11
Repeat, times 6
Reinstall the covers
DO not forget to put back the (I think) crankcase breathing pipe.
picture 12
You are DONE
skin to skin, about 60 minutes
Bought original MB spark plugs. Online from MB dealer got all 6 for about 84 USD delivered to home.
You can buy the NGKs or Bosch for 6-9 bucks a piece.
The MSRP on the plugs is 15 USD but I have seen them up to 25 on ebay.
picture 1
You will need a T30, Ratchet and a 6 inch extension.
It would be good to have a torque wrench so you can tighten your plugs to specs (more than I would have with a "naked" hand)
15-18 lb-ft
Take our the front cover of the engine, then the air cover with filters after removing both air ducts
picture 2
picture 3
picture 4
picture5
Then proceed with unscrewing the 2 torx bolts that hold the coil onto the plug
picture 6
picture7
Remove the spark plug: it needs a good effort
picture 8
Comparison of the 2 plugs, new and old
picture 9
picture 10
picture 11
Repeat, times 6
Reinstall the covers
DO not forget to put back the (I think) crankcase breathing pipe.
picture 12
You are DONE
skin to skin, about 60 minutes
Last edited by tiyyara; Jan 19, 2014 at 11:55 AM.
Senior Member
Joined: Aug 2012
Posts: 341
Likes: 1
08 C-Class (sold)
I just changed my spark plugs and the rubber things. but now I have a horrible knocking! The only thing i can think of is one of the plugs is not touching the spring. so Im going to take them all out and put them back in. What else could it be? NEED HELP ASAP.
thanks
thanks
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Senior Member
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08 C-Class (sold)
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Thread Starter
Junior Member
Joined: Jan 2014
Posts: 34
Likes: 0
From: Indiana
W212 E350 4 Matic 2011
Try making sure you "settle" the air filter assembly well
Once when I failed to do that I had the loud knocking noise
Otherwise my thought would be:
Misthreaded plug
Plug lacking "ring"
One cylinder not firing due to mis connection with solenoid
Once when I failed to do that I had the loud knocking noise
Otherwise my thought would be:
Misthreaded plug
Plug lacking "ring"
One cylinder not firing due to mis connection with solenoid
Newbie
Joined: Jan 2014
Posts: 13
Likes: 1
From: Kelowna, BC
2009 C Class 300 4Matic Sport
It could be that you didnt set your spark plug gap correctly. Im not sure what the gap is for w204 but every internal combustion engine has to be gapped to get proper spark.
Senior Member
Joined: Aug 2012
Posts: 341
Likes: 1
08 C-Class (sold)
So i took one new plug out and put a old one in. I found 2 bad spark plugs. Now I have 2 old plugs and 4 new ones. The car will idle for about a minute or so and have a little hiccups in the RPMs. I don't really know what to make of that? I think I'm just going to return the new plugs.
Member
Joined: Nov 2013
Posts: 166
Likes: 2
From: New York City
2009 C300 Sport 4Matic
Does anyone know a fair price to have this done at a certified mb indy / mb stealership?
I'd like to DIY this but I'm young and have no experience with a torque wrench. Also My car just turned 5 so I guess it's my time. Anyone know of adverse ramifcations of not doing this in a timely manner?
I'd like to DIY this but I'm young and have no experience with a torque wrench. Also My car just turned 5 so I guess it's my time. Anyone know of adverse ramifcations of not doing this in a timely manner?
Thread Starter
Junior Member
Joined: Jan 2014
Posts: 34
Likes: 0
From: Indiana
W212 E350 4 Matic 2011
Does anyone know a fair price to have this done at a certified mb indy / mb stealership?
I'd like to DIY this but I'm young and have no experience with a torque wrench. Also My car just turned 5 so I guess it's my time. Anyone know of adverse ramifcations of not doing this in a timely manner?
I'd like to DIY this but I'm young and have no experience with a torque wrench. Also My car just turned 5 so I guess it's my time. Anyone know of adverse ramifcations of not doing this in a timely manner?
I think 1 year or extra 10k miles should not be an issue.
But risks of going way over in my opinion could be:
1 suboptimal spark, hesitation, cat damage
2 plug getting stuck in head
Thread Starter
Junior Member
Joined: Jan 2014
Posts: 34
Likes: 0
From: Indiana
W212 E350 4 Matic 2011
You can check them, but if you remove them to check them you might as well replace them. You will be doing all the work when you examine them anyway
Senior Member
Joined: Aug 2012
Posts: 341
Likes: 1
08 C-Class (sold)
I tried gaping the new plugs to the old plugs specs. Now the engine won't start. I give up. I'm putting the old ones back in. I have changed spark plugs on other cars and never had a problem. I just don't know what I'm doing wrong?
Junior Member
Joined: Mar 2011
Posts: 18
Likes: 0
c300
I just changed out my spark plug yesterday. I think you shouldn't have to gap your plug, it should be already pre-gapped but if not, your owner manual should tell you what gap and what spark plug you should get. When you change out your spark plug, put a little bit of anti-seize on the thread.
My car runs more smooth now, I replace the air filter, change out the oil and filter, replace the cabin filter, flushed out my brake fluid and did a transmission fluid and filter change and it feels like a brand new car.
My car runs more smooth now, I replace the air filter, change out the oil and filter, replace the cabin filter, flushed out my brake fluid and did a transmission fluid and filter change and it feels like a brand new car.
MBWorld Fanatic!
Joined: Nov 2007
Posts: 2,078
Likes: 4
From: NYC
2012 C300 4Matic
Hey OP - no check engine light yet? If you get one you can pull the code and figure out which plug(s) it is.
MBWorld Fanatic!
Joined: Oct 2008
Posts: 2,601
Likes: 28
From: Atlanta, GA
2008 C300 Sport 6 Speed Manual, 1953 Chevy Bel-Air, 2015 Audi allroad, 1963 Chevy Apache
It's a good idea to check them before install to insure all are at recommended spec. One of the pre gaped plugs I bought for the Audi was way off and needed to be closed in a bit.
Super Member
Joined: May 2010
Posts: 816
Likes: 21
2008 W204
I noticed on the plugs I pulled out they had brown oil/grease on the threads, Im guessing applied by the factory to prevent the threads from bonding, I'm wondering if i should have put something on the plugs I put in, but don't know what it would be. Then again, if it was on the threads of the plugs I pulled out, Im sure there was more on the threads in the engine.
Member
Joined: Mar 2008
Posts: 105
Likes: 1
From: Seattle
2001 R129 SL500, '08-'20 W204 C350
It's been a few years, have you figured it out? Read somewhere the plug orientation matters? Maybe not? The NGKs seems to have the same orientation by looking at where the thread starts, does that mean they are indexed?
How about coil, need to replace after 110K miles? Dealer quoted $500 just plugs, Pelican has plugs only and plug/coil kit.
How about coil, need to replace after 110K miles? Dealer quoted $500 just plugs, Pelican has plugs only and plug/coil kit.
Last edited by Bobby204; Aug 30, 2019 at 12:29 AM.
