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CLA250 Spark Plug Replacement (DIY Definitive Guide)

This is a discussion on CLA250 Spark Plug Replacement (DIY Definitive Guide) within the CLA Modifications / DIY forums, part of the Mercedes-Benz CLA Forum category; The ngk plug was chosen specific to the m270 motor so the factory gap is within spec...

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Thread: CLA250 Spark Plug Replacement (DIY Definitive Guide)

  1. #11
    jmc
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    The ngk plug was chosen specific to the m270 motor so the factory gap is within spec
    traxem likes this.

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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.
    Last edited by coder; 01-06-2019 at 07:46 PM.

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    Quote Originally Posted by coder View Post
    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)
    Last edited by coder; 11-18-2018 at 05:17 PM.

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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?
    Last edited by coder; 11-26-2018 at 06:30 PM.

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

  • #18
    jmc
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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.

  • #20
    jmc
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    @coder
    Yeah I think I got most if not all the tools and tidbits ... should be fun!

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