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Discussion Starter #1
Hi,

I am changing out my Spark Plugs on my 2014 CLA 250 4Matic. I purchased the plugs from the dealer (NGK 270 159 07 00). They come pre-gapped at 0.024. The ones I pulled out which are the original ones are gapped at 0.025. AllData says it should be set at 0.032.

Has anyone ever changed out their plugs and if so, what did you gap your plugs at?

Thanks


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The Gap is most important, but all I can tell you now is that the NGK gap is smaller than the "Door Gap."
NGK says it is .028"
Rock Auto says .028"
Mitchell1 says .8mm which is .0314961"
Not listed at all in the CLA owner's manual, or even the Emissions Label as far as I can tell.
In a case where there are so many differences it is best to check directly with your MB dealer OR, JMC who I trust on matters such as this. Please come back here and tell us the answer. Sorry.
 

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Discussion Starter #3 (Edited)
Thanks Geo. Who or what is JMC?

From what I have read, a wider gap means a hotter spark which in turn leads to a leaner condition. So likely if I stick to 0.032 it will save on gas mileage.

I have a call into the dealership tomorrow. I’ll update this thread with what they tell me.


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"JMC -Who or what...?"
MB Expert and NINJA rated on this Forum.
I believe he is resting at the moment, but I'm sure he will appear here soon.
 

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Naaah not an expert just a car nut
For the M270 should be the SILZKFR8E7S plug
Gap is 0.7mm and should not preenlarge since the gap widens over time as electrode surfaces wear (despite fancy iridium and/or platinum materials)
0.028” ~ 0.7mm
 

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0.024” ~ 0.6mm
Thats 100 microns difference which is a lot (though thats only 125% of a typical hair)
How are you measuring the gap?

The door gap data is however a very closely guarded piece of data .....
 

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Discussion Starter #8
Thanks @jmc !!
You are indeed an expert because the dealer just called me back. They looked it up for me and said it should be 0.028 so you nailed it. I am measuring the gap using a gap gauge.

Couple more questions. Do you use anti-seize on these plugs? Also, one of those gray plastic square tabs on the ignition coils broke. Guess it’s just brittle from age. Do you know where to get a new one from? Dealer said they don’t sell it separately.


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Surprised the dealer is speaking nonmetric
Presume your gauges are super clean with no surface features nor oxidation
And must be used plane parallel to the electrode surfaces else a thinner gauge will be the read

Consider sourcing a preowned coil subassembly from ebay or something to replace the busted one

These plugs are only torqued at 23nm / 17ftlb so I dont use any coatings ... just need to make very certain the threads in the head are clean
 

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... best to check directly with your MB dealer OR, JMC who I trust on matters such as this. Please come back here and tell us the answer ...
Appreciate your confidence sir!
 

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Discussion Starter #11
Thanks again @jmc
I am using a lint free cotton swab soaked in carb cleaner to clean out the threads. The plugs I pulled had a bit of rust so want to make sure the new ones seat well.


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No worries @Aguila-Uno
A narrow tube hooked up to a (strong) vacuum cleaner and a plastic angled tooth cleaning pick (plus patience and a bit of luv) may work to clean the head threads which is critical as you already noted the contamination on the extracted plug threads
The plug threads in indeed easier to clean though run a fingernail through them to feel for any lumps or burrs which will affect torque accuracy which may somewhat impact ground electrode positioning
 

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Discussion Starter #13 (Edited)
I cleaned out the threads with carb cleaner soaked swabs and they were pretty dirty and rusty. Well worth the time. For the plug gaps I was measuring at an angle so thanks for the tip again. Got the gaps right and all buttoned back up and no codes :). I must say though. This job was a major pain in the rear. Worst part is the intake pipe but worth it as they were charging around $520 for the job.

The door gap though continues to be a mystery...
 

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Good show glad your motor is all plugged up
Dealers will charge $$$$$ to figure out and maintain our door gaps ...
 

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Maybe this will help as well (screenshot from a service manual).
They also say you need to apply anti-seize grease to prevent damage next time you remove the coils. They do not provide any specifications for the grease, just an order # and also they say you're not allowed to use any other kind of grease; I'm not so sure about that though. I imagine the greese needs to be conductive and temperature resistant, but I will investigate a bit more about it. Need to replace spark plugs myself soon.


65252
 

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Discussion Starter #16
@jcdenton I did use anti-seize on the coils. Got it from the dealer. It was not too expensive. I wanted to play it safe and go with their recommendation although I think I could have got by with some dielectric grease. l typically use it to keep moisture out and to help when I have to remove them in the future. I can send a pic or part number when I get home. Good find nevertheless.


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I purchased the NGK iridiums SILFKZR8E7S @ 110,000 km, and installed at a local German auto repair shop for over 3 weeks now. The car is running fine and no difference in overall performance (acceleration/idling smoothness, idling rpm, engine temperature). Gas consumption is also same as before (the engine was running fine before the replacement).
 

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110kkm almost 70kmi wow good to know the iridium-platinum path holds up well
 
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