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Discussion Starter · #1 · (Edited)
This guide will walk you through a 60k spark plug service for the CLA250 M270 engine. Service manual recommends changing the plugs every 60k miles. I did mine @ 63569. The internet has very scarce instructions/video at this point. Most CLA owners probably has not reached 60K yet. Special thanks to youtube channel @UnboxWorld for making a video for the 1.6T engine.

Make sure the engine is cold and the car is in "sleep mode" before doing any of these steps. Keep the keyfob away from the car and open the driver side door. The car is in sleep mode once the interior lights turn off. At this point, do not wake the car by closing/opening any of the doors or the trunk.

Tools needed:

Torx set
Socket / ratchet set (with extensions)
Flat head screwdriver
3pcs 18.5 oetiker clamps
Oetiker wrench
14mm 12 point spark plug socket THIN WALL
Torque wrench (very important!)

Air compressor
Blow gun
Vacuum

4 spark plugs (NGK SILZKFR8E7S)
Spark plug lubricating grease A002-989-80-51

STEP 1
Remove the 3 torx screws from the airbox neck (green circle) and loosen the two hose clamps (red circle).

20181007_142915.jpg

STEP 2
Detach electronic connectors (green arrows), then detach vacuum lines (red arrows). There are a lot of videos on how to remove oetiker clamps. All you need is a flathead really.
1. Vent line
2. Wide open throttle heater element vent line
3. and 4. purge lines

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STEP 3
Remove the intake pipe by sliding it to the left. The intake pipe will need to go under the non-removable cables (see first picture)

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STEP 4
Detach electronic connectors from the coils.

STEP 5
Remove the coil screws. Note that the spark plug boots are at an angle. You may use the ring spanner side of a wrench to pull the coil, using the pull tabs.

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STEP 6 (VERY IMPORTANT)
Prior to removing the plugs, use compressed air to blow gun loose debris. You don't want any debris falling off in your cylinders when you remove the sparks plus. An air can is a no no. Use compressed air with at least 90psi pressure.

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STEP 7
Using your spark plug thin-wall socket, slowly turn counter-clockwise. Mercedes does not recommend using anti-seize on the threads so you will hear metal to metal as you turn. There will most likely rust too (as mine did).
Remove and replace plugs one at a time.

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STEP 8
Since rust from the thread might have fallen off inside the cylinders, it is a good idea to vacuum the canal before installing new plugs. I just improvised and cut a piece of tube and shrink-wrapped it on my vacuum extension.

20181021_155408.jpg

Continued...
 

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Discussion Starter · #2 ·
STEP 9 (VERY IMPORTANT)
Put in new plugs and hand-tight clockwise first, then torque the plugs to 17 ft/lb using your torque wrench.

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STEP 10
Lubricate the tips of the boots and reinstall everything back.

20181021_155943.jpg
 

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Very cool! Glad you found ways to release the intake pipe ... thats the biggie.
Presume you managed to source the new clamps? Dealer special?
Was that one plug actually different in terms of deposits?
Did you use a drop of thread lube before reinstalling despite the “dry” recommendation? (the dissimilar metals thing....)
Wonder if that boot "grease" is dielectric gooo ...
Hope your car now drives better with mpg maintained ... the sparkers were updated and no details on why but they “look” the same and might have to section them to see what the deal is between the two variants
 

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Discussion Starter · #5 ·
Very cool! Glad you found ways to release the intake pipe ... thats the biggie.
Presume you managed to source the new clamps? Dealer special?
Was that one plug actually different in terms of deposits?
Did you use a drop of thread lube before reinstalling despite the “dry” recommendation? (the dissimilar metals thing....)
Wonder if that boot "grease" is dielectric gooo ...
Hope your car now drives better with mpg maintained ... the sparkers were updated and no details on why but they “look” the same and might have to section them to see what the deal is between the two variants
Amazon has the ear clamps. There are other brands too but I went with the oetiker brand. Plugs from cylinders 2,3,4 had the most carbon deposit. Very black. Plug from cylinder 1 was just brown, but all 4 had rust on the threads. I didn't use any anti seize. The car definitely drives like new! I'm surprised how these plugs change that engine's subtle character as they age. New plugs, in effect, is a semi tune-up.
 

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Good! Finally someone to back me up — plugs can make a difference ... even iridium tips wear at a less than ideal rate ... have to do mine at 25k.
That one plug is what we “want” to see but I wonder if the other three is what we “should” see cuz of the direct injection low squirt multispark operation ... and if those three are already like that can you imagine the combustion chamber? So that one (cleaner plug) chamber has a slightly different compression ratio and different combustion characteristics ... perhaps Omar or someone with aux injection can show what their plugs look like?
 

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Should be pregapped ... however trust but verify is my moto ...and can get variance over a 4 sample while we are at it
 

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Discussion Starter · #9 ·
Do you have to gap the plugs before installing them?
I only gapped it with eyes lol. I installed it as is. The plugs come gapped from the factory. But I agree with @jmc. A good idea to verify since your car will have it for the next 50k miles.

Sent from my SM-N960U using Tapatalk
 

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I only gapped it with eyes lol. I installed it as is. The plugs come gapped from the factory. But I agree with @jmc. A good idea to verify since your car will have it for the next 50k miles.

Sent from my SM-N960U using Tapatalk
I haven’t changed plugs in almost 20 years. Never kept a car long enough to do it. I did remember having to gap them. Are these plugs specifically pre-gapped for the CLA or is it just common now not to gap them?
 

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The ngk plug was chosen specific to the m270 motor so the factory gap is within spec
 

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Is it a given that you Destroy the oetiker clamps when you take them off?
IN other words, should I order the 3 new ones before attempting the job?

It looks like once the a removed, they are not reinstallable. That is fairly important to know.
 

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one more question

It looks like, if I remove the plastic collar that is held in place with the 3 torx screws, I would not have to remove the
clamp that couples it to the air pipe. Or, if i take off the clamp, then the collar could be left attached, no?

Looking at the video, that is what the guy seems to have done there.
Would the collar interfere with access to the last plug?

I think the air filter cover could be just popped off with the collar left in place.
I am about to do the job, will post an update when i am done.

Not a bad idea to gain access to the air filter housing and cleaning it out
like I see you did. :)
----------
On using anti-seize: do not.
It is not recommended to put anything on the spark plug threads,
because it would lubricate the threads, and alter the torque needed for correct orientation.
Applying anti-seize will likely result in over-tightening the plug.
In this case, we know that the plug's threads have shell plating, which acts as an anti-seize.
There is an NGK tech bulletin complaining about folks using anti-seize on their plugs and the
bad mojo that will result. So AFAIK this is not a superstition.
 

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Discussion Starter · #14 ·
Is it a given that you Destroy the oetiker clamps when you take them off?
IN other words, should I order the 3 new ones before attempting the job?

It looks like once the a removed, they are not reinstallable. That is fairly important to know.
Yes oetiker clamps are for single use. Make sure you purchase 3 18.5 ear clamps.
 

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More spark plug questions

Yes. ordered them clamps from Amazon. Was impossible to get locally. Thanks for the writeup.

On your picture #2 The throttle heater element vent line :
The clamp on this looks bigger than the other 2.
Just measured that pipe, it is around 22mm, so I do not think the 18.5mm clamp can fit there.
On later pics, it seems you unscrewed the plastic piece from the air pipe body altogether.
On the first pic below the caption "Other pictures". The red arrow @2:
Does that piece easily pull out of the air pipe body? Maybe the clamp would not have to be released
at all then.

I notice after 3-4 years of driving a lot of the plastic pieces (brackets) become brittle.
I broke a couple just poking around.

What is the purpose of the dielectric grease? To keep moisture out? I usually just spray the connections
with a high grade contact spray (deoxit)
 

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Elctrical D connector detach?

There are only 2 Oetiker clamps that need to be taken off.
The thick hose kinda just pulls out of the air tube body, as shown on the photos. comes lose with a bit of
wiggling.

Call me dumb. i had a tough time figuring out how to detach the couple of electrical harnesses that needed to come off.

These things have a gray square tab. This needs to be slid _sideways to unlock,
parallel to the centerline of the wire, (in the direction you would pull the connector off. Somewhat similar to the VW connectors.

There is a small space where you can get under the tab from the side with a small flat head, and slide it in the indicated direction.
Think of which direction you would pull the cable connector to disconnect it.
That is the direction you should move the tab to unlock.

The ignition coils may need to be disconnected from their wire harness as well, although I was able to do the 2 left ones
without disconnecting .

The air tube has an orange rubb inner collar. This can pull out of the black outer tube and stay on the turbo inlet.
You need to push the outer tube back onto the inner tube and try to pull both off the inlet together.

The air tube is an utter pain to remove. The permanent cables may be lashed on pretty tight so there is not a lot of
room to maneuver when you try to pull it out. . The outer tube has some positioning ears and because of this you have to put the hose clamp back
in the same position where it was. It has a little pocket where the worm screw part need to fit into.

Overall, this is not a straight forward job and there is a non-trivial chance that an inexperienced person will break or damage
some plastic part.

The ignition coils are held in place with a pair T27 torx screws each.
started around 3 pm today, took it apart by 6 pm, finished at 9:30 pm.

Putting back the air pipe onto the turbo intake gave me a fight. As I mentioned above there is an orange inner rubber collar which fits over the turbo intake
I found it impossible to push the intake back on with the rubber collar fully inserted into the outer pipe. It just would not slide all the way up.

OTOH taking out the rubber collar, I could easily put that back on, but then the geometry of the parts just would not let me get the outer pipe
over and onto the collar, just not enough space to make it work.

After screwing around with it for an hour or so, ended up inserting the rubber collar into the outer pipe first, but I was able to pull it out a bit once all the pieces were
more or less in position. so it was sticking out maybe a half inch. Then I was able to get the rubber collar in place all the way, then I was able to
push the outer pipe home.

The plugs look a bit rusty but ok. The gap still good, no iridium pieces missing. The car was running fine having 86K miles on the plugs .
If I drive careful I would tend to get insanely good highway mileage. 45+ mpg if I keep it under 65mph.
Will see how the mileage is with the new plugs.

Runs fine but it did run fine with the old plugs too. I am not sure it is running any better with the new plugs.
I am just glad it started up and runs. I finished the job out of stubbornness, not sure if I would want to do it again.

Leave it to MB to make a simple job such as this totally DIY hostile. A plug change on an inline 4 should be a 20 minute job, given easy access to the
ignition coils/plugs. Do these guys have any concept of designing for maintainability? I imagine the trained Benz techs have some specialty tools
the make the job easier and probably know some tricks to speed it up. But still, it is a painful exercise even for them I imagine.

Did I mention small parts falling into the engine compartment and getting caught by the mud plates?
Before deciding to do this job, consider how much your time is worth,
and whether you have enough experience, patience and stubbornness to see it through.

Knowing what I know now, I would just leave the plugs alone until I notice some symptom,
or seriously consider paying someone to to the job. I was fat dumb and happy until I read here on this board that the
plugs needed to be done. In Asian cars, It is not unusual for iridium plugs to run 120K miles without any problem.
I our 2005 Toyota Sienna, we did 220K miles with the original factory (iridium) plugs. It was still running fine
when we traded it in.

Does anyone know how much the dealer charges for a plug swap?
 

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Discussion Starter · #17 ·
My local dealer wanted $517. An independent shop wanted $150 so I was skeptical If they did a CLA before.
 

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Re plug life ... the multispark scheme wears them out quicker than typical single spark systems. So Ir was chosen to give plugs a chance at some mileage. But even Ir wont last forever. Pretty sure the car will run on old plugs though combustion efficiency and clean burn will undoubtedly suffer ... mpg is one thing ... stressing the cat is another.
Not sure if I look forward to this plug exercise though I do need to see the residue condition and observe the chambers anyway so might as well give it a go ...
 

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Jmc,

Make sure you have enough time, and have all the tools before you get started.
Easy to forget:
-A stubby screwdriver, preferably one that does not let the bits fall out of the bit holder.
-A torque driver that goes down to 17 foot pounds. (I have 2, and one of them had a lowest setting of 25)
-T27 case hardened torx bit. (some sets are missing this)
-The spark plug socket is non-standard. (22mm thin wall)
-18.5mm Oetiker clamps ( need 2)
-Oetiker clamp setting tool. (pliers may work)

I did not use the Mercedes dielectric grease. Just sprayed the inside of the Ignition coils with deoxit contact spray.
(The dielectric grease may have better high-temp behavior).
Getting the ignition coils off took a lot of pulling and jiggling. Using a closed ring end of a wrench and hook it around the
pull tab was helpful.
Blowing out the plug wells with an air gun is good advice. I had dry leafs there.
 
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