2014 ML550 Spark Plug Change
02-06-2018, 12:47 PM
#1
Newbie
Thread Starter
2014 ML550 Spark Plug Change
Has anyone done this service on a vehicle with the V8 engine that comes in the 550. I have seen threads for the ML350 6-cylinder.
Thanks in advance...
Thanks in advance...
02-06-2018, 01:33 PM
#2
Super Member
I have and it can be a real pain for the rear cylinders 3,4,7 & 8. Just takes some patience and time.. Not a quick maintenance job by anyone.
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PreciousMetals (02-06-2018)
02-06-2018, 01:52 PM
#3
Newbie
Thread Starter
Are there any special tools that are needed to perform this maintenance, or any special precautions? I am rather handy around a car, but the right tools make all the difference. This is my first MB.
02-06-2018, 09:00 PM
#4
Member
I would assume you would need the 12 point 14mm socket for the spark plugs. And a good torque wrench. Not sure if it’s different for the 550, but the 350 has indexed plugs so it’s important to torque them correctly.
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PreciousMetals (02-07-2018)
02-07-2018, 09:25 AM
#5
Member
I forgot to add, you may want to search for a write up on changing the plugs in other models, that have that 5.5l motor. There wasn’t a write up for the 3.5l for the W166, but I found a write up on the same motor in a different car and it was exactly the same.
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PreciousMetals (02-07-2018)
02-07-2018, 10:12 AM
#7
Member
I didn’t use a special tool for the coil packs per se, but you may have to be a little creative. Check out the post below and look through that write up. There’s one part where the guy used rope and a piece of wood. I did have to do something similar on the cylinders close to the firewall. I can’t think of anything else that would be special, but like I said glance through this write up and see what all he mentions. You may want to use some dielectric grease between the coil pack and spark plug. The issue of it sticking that’s mentioned in this write up was the same for me.
https://mbworld.org/forums/attachmen...eplacement.pdf
https://mbworld.org/forums/attachmen...eplacement.pdf
Last edited by NickW; 02-07-2018 at 01:27 PM.
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PreciousMetals (02-07-2018)
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02-07-2018, 01:30 PM
#10
Member
If you have the correct spark plug, then when you torque it to the specified torque, it should be at the correct position. You can only torque the plug once, you can't loosen it and re-torque it because it will have stretched and the washer compressed and will not land in the same position.
Also, take care with the clips on the coil packs. The tabs that lock them on are easily broken. You may want to have some spare connectors on hand in case you break any. They are only a few bucks each from MB.
Also, take care with the clips on the coil packs. The tabs that lock them on are easily broken. You may want to have some spare connectors on hand in case you break any. They are only a few bucks each from MB.
02-07-2018, 02:23 PM
#11
MBWorld Fanatic!
I am learning about indexing of the spark plugs. Am I wrong in saying there is no harm in NOT indexing the spark plugs? I am reading that the engine may produce around 1% less HP if the plugs are not indexed on my ML. Will there be any harm done to the engine/normal performance of the engine if indexing is not done?
Like I said, I am trying to learn. So, please pardon my ignorance on this subject.
OP, didn't mean to hijack your thread. My question is kind of related to the topic of this thread.
Like I said, I am trying to learn. So, please pardon my ignorance on this subject.
OP, didn't mean to hijack your thread. My question is kind of related to the topic of this thread.
02-07-2018, 02:44 PM
#12
Member
If this was on an old beater, then I would say don’t worry about it, but I wouldn’t consider these vehicles old beaters just yet! All you have to do is torque the plugs to the proper torque spec, so I would just do it correctly. It’s really not difficult. If you don’t have a torque wrench, it’s a worthy investment to buy one if you do your own work.
And no no worries man, ask away!
And no no worries man, ask away!
12-18-2019, 08:43 PM
#14
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2017 GLE350 4MATIC
Using Google and the search button on this site, it can be found that indexing the plug is accomplished through a thread geometry on both cylinder head and spark plug, combined with the proper spark plug torque. This puts the electrode orientation within an acceptable range of "pointing at" the fuel injector. In a worst case scenario, improperly oriented spark plugs can produce valve erosion and cause significant engine damage.
