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Spark plug replacement secret mystery

22K views 51 replies 23 participants last post by  redlightning 
#1 ·
I’ll try this again. Posted it about a year ago with no real answer. Is there a video on YouTube or whatever that shows the procedure involved in changing the spark plugs (that require changing at least twice as often as any vehicle currently produced). “Indexing” the spark plugs is unique. I know you can take it to a Mercedes dealer and pay $300.00 to change 4 spark plugs, but It’s just a spark plug change and there are how to videos on EVERY vehicle out except the Metris. Starts to make me wonder why.
 
#2 ·
There's not many videos on it because there's only about 26,000 of them on the road in north america so far, and of those, a huge number are part of fleets, and they aren't making videos about servicing their vans, nor are dealers. The number of people doing this job themselves who feel like filming it is probably close to zero. In my case, its something I'd consider making a video of, but I won't even need to do it for another 2+ years on mine...they're just all too new/too few for there to be much video coverage into repairs as the overall population of vans probably hasn't needed a whole lot of out-of-warranty/fleet/service support repairs.

The plugs are indexed. If buying factory original plugs, the indexing is likely accomplished by exactly following the install procedure, which likely specifies a very specific torque to complete the tightening process, which leaves the plugs in the correct spot as they are manufactured to be this way.

$300 seems a bit steep, but not unreasonable. Could also go to a euro-vehicle private shop where prices may be a bit lower (though around here they are nearly identical).
 
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#6 ·
I just replace mine with the NGK equivalent they were a few dollars less expensive and identical plugs identical to the point when they were put in place they were indexed in the same place the hardest part about this change is removing the foam sound insulator from the top of the engine. And the new need for a 14mm magnetic spark plug socket. For the install I marked both the socket and the extension I used and lined them up with a mark on the engine when I remove the plugs I installed the replacement plug in the same position to the socket and ended up with that Mark pointing to the same spot on the engine while there could be a couple of degrees of difference in the indexing a couple of degrees is not enough to affect the performance of the engine might’ve been in for about 6000 miles on a brighter note I will try and include a picture of the plugs that were removed. You can see the wear at the tip of the plug electrode this was 116,000 miles
17586
 
#9 ·
Hi fellas,

So I have my '17 Metris at the stealership for the 3 year maintenance, and they wanted to do a plug change as well - but my van only has 29k miles on it. Their service manual calls for a change at 45k miles, but I'm reading here that some of you have gone 75k-100k miles without changing your plugs? My stealership (DC metro area) wanted $500 for the plug change! :-O I'm inclined to do this job myself, when the time comes... thoughts?

- Justin
 
#10 ·
One of the Southern California stealerships is asking $530 to change plugs. I didn't realize that the plug change schedule was separate from the ServiceA/B cycle or I would have changed these earlier. It seems the plugs cost around $50. Is it really that hard to get to them and torque them correctly?
 
#11 ·
No wonder everyone hates dealers....that's ridiculous. It's fairly straightforward. Took me maybe 1.5 hours...and I went slow because I wanted to mark the plugs to see if they were indexed. They didn't seemed indexed....well they were all within 90° of center...so I guess somewhat indexed. That's about what the new ones were like. I hate auto dealers...they are cons. Most of the techs are good people.
 
#12 ·
I'm due for my plug change. I'm being quoted $475 from the dealers here. Though I can get that down to $425 with a service coupon...still a lot. Or I can drive 2 hours to an indy shop with a great reputation and get it done in the $200s.
 
#14 ·
Newbie question with regards to indexing, marking, etc.

What exactly is/are the concern(s)?
Proven or over-caution?

I have done a good number basic services on outdoor power equipment, including spark plugs. Always buying either the manufacturer one or equivalent or better, depending on what is available, cost etc. Due to the actual thread cut, things only line up one way, and then it is down to the number of turns to get it appropriately hand tight (or spec torqued). So, not being a mechanic or around them, I have not heard of indexing, nor marking something like spark plugs. I thought it was just a very quick undo to remove and install the replacement.

If the dealer, really wants $500 to do it ... then I will be looking at doing it myself, if I can't find an EU indie mechanic.

MB probably has specified torque they want spark plugs installed at, right?

As far as MB wanting stuff done early. (grumbles) Our new MB service adviser and the follow up quality assurance call from the service department head T'd me off two weeks ago. With insistence that oil and fluids by the book need replacing at a specified time interval, and not simply due to miles driven. Officially you have to. Right. A person has about 1/3 rd of the miles on the vehicle vs odometer count, the car is 3 years old, essentially new, still has new car smell and everything ... and somehow these MB approved fluids now expire / go bad in three years??? I Don't Think So.
Sure it is cautious to replace everything every few years ... but this is not a race car ... and to the tune of $500 - $1000 and more, it is easy to say it has to be done; when they're not paying the $$$$ bill ...
 
#16 ·
As far as MB wanting stuff done early. (grumbles) Our new MB service adviser and the follow up quality assurance call from the service department head T'd me off two weeks ago. With insistence that oil and fluids by the book need replacing at a specified time interval, and not simply due to miles driven. Officially you have to. Right. A person has about 1/3 rd of the miles on the vehicle vs odometer count, the car is 3 years old, essentially new, still has new car smell and everything ... and somehow these MB approved fluids now expire / go bad in three years??? I Don't Think So.
Sure it is cautious to replace everything every few years ... but this is not a race car ... and to the tune of $500 - $1000 and more, it is easy to say it has to be done; when they're not paying the $$$$ bill ...
I mean this in all respect, ICERabbit, but you are entirely wrong. It is entirely possible that the oil in your van is fine. It is also possible that it is in desperate need of being replaced, depending on a variety of factors that include temperature, relative humidity, operational load when you are using the vehicle, the condition of the oil filter based on these uses, and other factors.

The bigger issue, though, is the overall condition of your van. Your van, or any car, really, needs to be inspected at least once a year by a person who is familiar specifically with the design and engineering procedures of vehicles made by its manufacturer. Various things can happen over that year that create a safety or operational issue. An improperly secured line carrying fuel or brake fluid or coolant can, for instance, start rubbing against a component and approach a point where it is going to leak. Bolts, screws, and similar things can begin to work loose. Mice, squerils, and other animals get into cars and make messes of various kinds.

You are also going on about it not being a race car. My friend, 104 bhp a liter was very much race car performance levels just a few decades ago! Do you remember Saab’s competitor to the E36 M3? It was called the 9-3 Viggen, and it used a 2.3 turbo four making 230bhp (the M3 made 240, remember), which is 100 bhp liter. These are high precision, high stress engines. They require much more rigorous maintenance than older, simpler, less powerful, larger engines.

I do not dispute that MB dealers charge very impressive amounts of money for relatively simple service, and if you can find a Mercedes-qualified person elsewhere, I get that. But trust me, replace the fluids that are supposed to be replaced at roughly the time or mileage they are supposed to be replaced at. You might find this maintenance expensive, but its gon nothing on the repairs you will end up having down the road from not observing it!
 
#15 ·
I have no position on this, but you index using washers to change the thread depth so when you torque you can pick the final orientation of the gap to face the intake valve. The material on spark plug manufacturer websites suggest a benefit of 1% in hp by doing this correctly. NGK makes a minor comment that it's maybe not worth the effort in most cases.

Getting within 90 degrees seems pretty good.
 
#17 ·
Thanks.

My point about race cars really was that they'll 100% do whatever (new oil, fluids, plugs, filters, tires, etc.) prior to any given day on the track. That is not consumer driving. We drive conservatively, no autobahn in NA, no red-lining. And, it really is not about not doing the work at all, but rather when it is reasonably due based on miles driven as indicated by the book & on board computer. When a MB is 3 years old, does ~5000 miles / year, has 16000 miles, is in a controlled temperate environment, garaged 99% of the time, no humidity, no critters, ... during dormant times I make sure it gets driven briefly once a week and for an hour or two every two weeks. And, yes, it gets it annual checkup, change the engine oil + rotate the tires. Good. Rest checks out AOK = see you next year.

IMHO the other fluids etc have not expired in three years, compared to a car that actually put all the miles on the odometer ... when some of these things used to be for 60k miles or 100k miles on the book with a prior MB. I am perfectly happy having an oil change performed when the engine is new, after first 1000-1500miles or so. Used to do those in 80s & 90s, then was told no longer needed, don't worry about it. Or the once or twice a car came into the family without known track record, I'll have the extra work done, do the fluids, belt. Done. But, the whole your new car is 3-4 years old now, time to $$$$, even though you only have 15k 20k miles and can barely distinguish it from a new car ... seems just a bit over-done. My wife's car ended up having its 40k service TWICE. First time because they figured it was due at 4 years with 33k or whatever. Then boom the next year it was over 40k, year 5, they did it again, without asking and not even checking their own records. I ended getting a full refund on that one.

Anyway.

Back to indexing. I will read up. :)
 
#20 ·
Well, my dealer service scheduler cheated me out of the MB 250 off 500 coupon by pushing me back 2 days after expiration date saying 'don't worry about the date it will be ok'. Then only to get a call from my SA saying that MB will not honor coupon since it's expired. Long (argue back forth) story short, I declined the 'increased price' $535 cost...so now I'm at 55,000 miles on these original plugs. Lesson learned, don't trust the underpaid,overworked desk lady.
 
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#21 ·
That's a shame. Are you serious about the $535 just for plugs and maybe topping up the washer fluid? Well, poor dealer owner has yacht, jet and multi home bills too! I would trust anyone to change them out. You don't need to be a master tech. And you are slightly over, so don't worry too much. When I changed mine around 50k miles they looked great.
 
#22 ·
Yes.... just plugs. This is Mercedes of South Charlotte. They will only see me for ELW work. Other local Benz dealer quote was $475.
 
#25 ·
Just did mine with the NGK Japan 90654/SILZKFR8E7S plugs I got from Rockauto. This is the OEM plug. The old plugs looked pretty burnt and rough but came out nice and easy from the cold engine; my van just hit 91K miles. The replacement plugs looked identical only without the MB branding. I simply properly torqued them, did no indexing. The van runs as good as ever!

 
#32 ·
This dealer has treated me fairly well in the past. I just called another dealer (that is closer to me) and they are asking $850 to change the plugs. They have a wait list of about 3 weeks to get the vehicle in. Transmission fluid and filter is almost $1000 at both places. Rear differential fluid change is between $300 and $400. Prices for this kind of service seem to have increased with a much larger jump than the basic inflation we've seen in the economy over all. The first dealer talked about MB technicians being really hard to find and expensive to feed so their prices have gone up. I'm not sure if the dealer just wants me to pass so their overworked techs can work on the more expensive luxury cars or if these are their legitimate prices now.
Not sure where you’re located, but those prices seem like twice as high as they should! Just because it’s a Mercedes doesn’t mean another good mechanic couldn’t do the work.
 
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