GLK-Class (X204) Produced 2008-2014

GLK350 Sprark Plugs - DIY

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Old Apr 9, 2025 | 07:12 AM
  #26  
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Iridium plugs last longer than platinum and are 13 original . They last 110000-130,000. Coils can last the lifetime of mb. Parking outside in wet climates or extreme heat probably shortens life . I noticed no difference with new plugs at 80,000 and plug condition was very good. Plugs boots must be replaced at every change or you will most likely have misfires . I had my mb run on 3-4 cilinders because I was cheap and tried re using old plug boots . I would not change at 80,000 again knowing how good plugs were . Also get genuine mb plugs. I went to autozone and they referenced the wrong heat range plug, then there is the known NkG Counterfeit plugs and I’m sure alot more. For MB most components should be MB or known parts that companies like FCP euro sell. FCP also has a life time warranty, I’ve used it , it’s for real ! Spend the money on more oil changes rather than plugs if your MB runs well.
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Old Apr 9, 2025 | 07:29 AM
  #27  
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Originally Posted by Mmr1
Iridium plugs last longer than platinum and are 13 original . They last 110000-130,000. Coils can last the lifetime of mb. Parking outside in wet climates or extreme heat probably shortens life . I noticed no difference with new plugs at 80,000 and plug condition was very good. Plugs boots must be replaced at every change or you will most likely have misfires . I had my mb run on 3-4 cilinders because I was cheap and tried re using old plug boots . I would not change at 80,000 again knowing how good plugs were . Also get genuine mb plugs. I went to autozone and they referenced the wrong heat range plug, then there is the known NkG Counterfeit plugs and I’m sure alot more. For MB most components should be MB or known parts that companies like FCP euro sell. FCP also has a life time warranty, I’ve used it , it’s for real ! Spend the money on more oil changes rather than plugs if your MB runs well.
I guess the worry is that the spark plugs gets stuck if left for too long next time you remove it.
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Old Apr 9, 2025 | 07:54 AM
  #28  
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Ive never heard that, its not in the manual, if that were so than 10,000 miles would be a risk and there would be a class action against MB
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Old Apr 9, 2025 | 08:16 AM
  #29  
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Originally Posted by Mmr1
Ive never heard that, its not in the manual, if that were so than 10,000 miles would be a risk and there would be a class action against MB
It is mainly caused by corrosion, 10,000 miles won't cause it.
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Old Apr 9, 2025 | 08:18 AM
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Some people put anti-seize on it for that reason but please don't https://mbworld.org/forums/e-class-w...2017-e300.html
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Old Apr 9, 2025 | 08:54 AM
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Maybe yes if car is left outside in certain wet salty climates or if another person changed them and overtightened them . But I’m not a mechanic so I don’t really know . They are closed in well on a mb unlike other cars I’ve had that are exposed to weather. I do know by how mine looked and ran they didn’t need replacing when I had it done .
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Old Apr 9, 2025 | 09:56 AM
  #32  
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Originally Posted by Mmr1
Maybe yes if car is left outside in certain wet salty climates or if another person changed them and overtightened them . But I’m not a mechanic so I don’t really know . They are closed in well on a mb unlike other cars I’ve had that are exposed to weather. I do know by how mine looked and ran they didn’t need replacing when I had it done .
Good to hear.
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Old Apr 9, 2025 | 10:46 AM
  #33  
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Anti seize on spark plugs is for unplated plugs in cast iron cylinder heads. Modern spark plugs have nickel plating to avoid seizing in the plug holes. This and the fact that they are being installed in aluminum cylinder heads is also factored into the tightening torque. Using anti seize compounds risks stripping the threads in the heads. Adjusting the tightening torque is approximate at best. On top of that, copper anti seize compounds are never recommended for aluminum because of galvanic corrosion.
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Old Apr 9, 2025 | 11:43 AM
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True, I would follow mb procedure for all this. No anti seize, no re gaping of plug, unless your super careful as you easily crack the insulator
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Old Apr 9, 2025 | 12:40 PM
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Originally Posted by Odd Piggy
Anti seize on spark plugs is for unplated plugs in cast iron cylinder heads. Modern spark plugs have nickel plating to avoid seizing in the plug holes. This and the fact that they are being installed in aluminum cylinder heads is also factored into the tightening torque. Using anti seize compounds risks stripping the threads in the heads. Adjusting the tightening torque is approximate at best. On top of that, copper anti seize compounds are never recommended for aluminum because of galvanic corrosion.
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Old Apr 9, 2025 | 12:42 PM
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Originally Posted by Mmr1
True, I would follow mb procedure for all this. No anti seize, no re gaping of plug, unless your super careful as you easily crack the insulator
The beauty thing of OEM MB plugs are that they are pre-indexed, so just install and done.
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Old Apr 9, 2025 | 12:53 PM
  #37  
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Originally Posted by W205C43PFL
The beauty thing of OEM MB plugs are that they are pre-indexed, so just install and done.

The true beauty would be no indexing needed.
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Old Apr 9, 2025 | 01:45 PM
  #38  
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Originally Posted by MBKLUE
The true beauty would be no indexing needed.
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Old Apr 9, 2025 | 02:25 PM
  #39  
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Wow, I had no idea changing spark plugs was so complicated. It never was when I did it. I've never had a problem.
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Old Apr 9, 2025 | 02:59 PM
  #40  
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Im reading up on these new Ruthenium plugs, but most people say the only real benefit is its longevity, and cost cheaper for manufacturer to make compared to platinum and Iridium, I'll just stick with the Bosch double platinums.
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Old Apr 9, 2025 | 03:11 PM
  #41  
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Originally Posted by Silver Shadow
Wow, I had no idea changing spark plugs was so complicated. It never was when I did it. I've never had a problem.
Clarification required. Are you referring to "choosing" or "changing"?

On our 2001 Wrangler with a straight six, the last time I changed them, less than 30 minutes (probably even blindfolded).

On the GLK? No idea, not done it yet, but my guess is it'll take me 30 minutes just to figure out a plug change game plan. 👍
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Old Apr 9, 2025 | 04:24 PM
  #42  
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FWIW - and only a single anecdotal example - but the plugs on my "project" 2012 (M272, thank goodness) were a bear to get out. You can see the entire swap process in the video (I went with some no-name plugs just to see if they actually last - or not, and because I got them free), but if you want to see the difficulty getting the original 159,000 mile plugs removed, start watching at 7:00... I was a little freaked out at how much torque it took to remove all the plugs, but happily, no harm done...

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Old Apr 9, 2025 | 04:38 PM
  #43  
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Originally Posted by habbyguy
FWIW - and only a single anecdotal example - but the plugs on my "project" 2012 (M272, thank goodness) were a bear to get out. You can see the entire swap process in the video (I went with some no-name plugs just to see if they actually last - or not, and because I got them free), but if you want to see the difficulty getting the original 159,000 mile plugs removed, start watching at 7:00... I was a little freaked out at how much torque it took to remove all the plugs, but happily, no harm done...

https://www.youtube.com/watch?v=Cj9xMMI-Bj4
That is a healthy amount of miles, thanks for sharing your video.
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Old Apr 9, 2025 | 04:51 PM
  #44  
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Originally Posted by calder-cay
Clarification required. Are you referring to "choosing" or "changing"?

On our 2001 Wrangler with a straight six, the last time I changed them, less than 30 minutes (probably even blindfolded).

On the GLK? No idea, not done it yet, but my guess is it'll take me 30 minutes just to figure out a plug change game plan. 👍
Both. If Bosch was OEM, Bosch it is.
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Old Apr 9, 2025 | 05:15 PM
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If using Bosch non mb non iridium be sure the digit-number is the same as iridium’s number . I was sold from a big auto store the wrong plugs they said “will work” temperature rating is critical to the motor. That’s why I gave up and went to a mb dealership. I knew what I got . At mb they are just printed MB so I can’t tell you the number . Ng are known to have counterfeit sold . and I don’t trust auto zone type of stores. I would trust FCp euro
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Old Apr 11, 2025 | 06:35 AM
  #46  
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When googling - searching Bosch or Ngk counterfeit spark plugs both come up with many descriptions. That is sad. Plugs that are the wrong heat range cold will carbon up the motor and take longer for the catalytic converter to warm up . Plugs that are to hot can melt with certain driving . Proper plugs are really critical to running the motor correctly . I used to play around with different heat range plugs when motors were fun to work on, a looong time ago . Buy from known reputable suppliers. And check them out first.

Last edited by Mmr1; Apr 11, 2025 at 06:49 AM.
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Old Apr 11, 2025 | 09:00 AM
  #47  
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Originally Posted by Mmr1
If using Bosch non mb non iridium be sure the digit-number is the same as iridium’s number . I was sold from a big auto store the wrong plugs they said “will work” temperature rating is critical to the motor. That’s why I gave up and went to a mb dealership. I knew what I got . At mb they are just printed MB so I can’t tell you the number . Ng are known to have counterfeit sold . and I don’t trust auto zone type of stores. I would trust FCp euro
Originally Posted by Mmr1
When googling - searching Bosch or Ngk counterfeit spark plugs both come up with many descriptions. That is sad. Plugs that are the wrong heat range cold will carbon up the motor and take longer for the catalytic converter to warm up . Plugs that are to hot can melt with certain driving . Proper plugs are really critical to running the motor correctly . I used to play around with different heat range plugs when motors were fun to work on, a looong time ago . Buy from known reputable suppliers. And check them out first.
Yes. Just buy from a dealership or FCPEuro, given these don't get changed often. It is worth the peace of mind.
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Old Apr 11, 2025 | 02:39 PM
  #48  
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All this talk of spark plugs reminds me why I don't want another gasser; why spark when you can glow?
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Old Apr 11, 2025 | 04:05 PM
  #49  
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Originally Posted by andreigbs
All this talk of spark plugs reminds me why I don't want another gasser; why spark when you can glow?
Or we can shine, like the MB star : )
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Old Apr 12, 2025 | 07:58 PM
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Did not use anti seize last time, no problems getting them out this time. Only thing that got stuck was the rubber grommet from socket on the first plug I changed and torqued down. I think just from age, but for the rest I bought a new magnetic socket plug. I actually tried putting the coil back on and was wondering why it wasn’t going in all the way, when I took out the coil the rubber insert was sitting inside the coil boot, and I pulled it out easily. Honestly if I realized the grommet was left behind before putting the coil back on, I probably would have had to remove the new plug. You can kind of see the rubber grommet around the plug in the picture attached.




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