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Changed my plugs on the S550, made a HUGE difference. idling is so much smoother and I feel HP gains, snappier acceleration too. Definitely recommend this 30 minute investment of your time. I used the Bosch Fine Wire Double Platinum plugs. YR7MPP33
The old plugs really didn't look too bad. A quick cleaning with a wire brush and a re-gap would probably have made them good as new. But I guess it made sense to change them since you had everything apart already. It's good to see that they are so easy to change. Did the coil packs come off easily? Was there a special tool to pop those off after taking out the screws....or did they come off by hand by pulling them out?
The old plugs really didn't look too bad. A quick cleaning with a wire brush and a re-gap would probably have made them good as new. But I guess it made sense to change them since you had everything apart already. It's good to see that they are so easy to change. Did the coil packs come off easily? Was there a special tool to pop those off after taking out the screws....or did they come off by hand by pulling them out?
Just had my S550 in for some routine service and the dealer recommended to go ahead and change them with 85k on the odo for a bargain price of $325 (not!) Think I'll be doing this myself, thanks for the info...
Mine had 80k on them. It's only about a $100 investment and about 30 minutes of time. It was so easy to change these on my 2007 s550 compared to my 01 c320 which needed 2 plugs per cylinder. Coil packs and plugs are all in one unit which makes it even easier.
Think all you need is a T30 torx to remove the coil packs. Then a spark plug socket and long extension. Make sure you tighten up the new ones all the way and put some anti-seize on the threads and your good to go.
80k? Mercedes recommends to change every 4 years or 40k miles. It's part of a major service. I'm surprised the plugs still looked that good after 80k miles.
80k? Mercedes recommends to change every 4 years or 40k miles. It's part of a major service. I'm surprised the plugs still looked that good after 80k miles.
False....Maybe for a S600 but not for S550. More like every 4 years or 91k.
I was told it's usually a 75k service on plugs, I was a little later than I usually would have changed them. I'll prob replace them after 50k next time. Easy and low cost maintenance.
Totally agree on ease of job,cost and result ,the car 98K/km drives so much better I wished I had done it before.
One very important thing Bensitto has also mentioned:
drive the spark plugs fully home : as with the torque wrench on the prescribed 25N/m it already klicked before the spark plug was all the way seated : after at least 1/8 of a turn it klicked again on 25N/m then it was fully seated..
That got me a little so I had to retorque the lot again on 25N/m.
Special spark plug wire tool needed to do this job?
I know you need to use one on certain models, like the e320.
Can you confirm that the s550 does not need the special tool to remove the plugs with out damaging the wires internally. Asking because I do not have that tool.
Indy shop wants $400 for the job, if it is that easy to do without that special tool then it may be worth doing at home.
Does the Bosch plugs with anti seize on threads already and pre-gap? Recommend to put on some anti seizeif it does not have it?
I know you need to use one on certain models, like the e320.
Can you confirm that the s550 does not need the special tool to remove the plugs with out damaging the wires internally. Asking because I do not have that tool.
Indy shop wants $400 for the job, if it is that easy to do without that special tool then it may be worth doing at home.
Does the Bosch plugs with anti seize on threads already and pre-gap? Recommend to put on some anti seizeif it does not have it?
Thanks in advance.
No 'special' tools needed. Just have a normal spark plug socket with an extension. For me, it helped to have one of those locking extension where you have to slide a tab to release the spark plug socket. Otherwise if I used a normal extension bar the spark plug socket would get stuck on the spark plug when trying to pull it out. Because of the V-angle there's enough clearance all around the engine to get a 8" or 10" extension. Use a torque wrench to tighten, as mentioned. As for the ignition coil assembly, it just pulls off after you unscrew the T30 torx screws.
I used the Bosch Yttrium spark plugs and they should be pre-gapped out of the box. Just check with a gauge before installing. I used anti-seize on the spark plug threads and some dielectric grease on the ignition coil boots when plugging it back. Engine runs great.
No 'special' tools needed. Just have a normal spark plug socket with an extension. For me, it helped to have one of those locking extension where you have to slide a tab to release the spark plug socket. Otherwise if I used a normal extension bar the spark plug socket would get stuck on the spark plug when trying to pull it out. Because of the V-angle there's enough clearance all around the engine to get a 8" or 10" extension. Use a torque wrench to tighten, as mentioned. As for the ignition coil assembly, it just pulls off after you unscrew the T30 torx screws.
I used the Bosch Yttrium spark plugs and they should be pre-gapped out of the box. Just check with a gauge before installing. I used anti-seize on the spark plug threads and some dielectric grease on the ignition coil boots when plugging it back. Engine runs great.
Also, make sure when you are tightening up the new plugs that they are seated all the way down. It can feel tight towards the end but you may need another turn or two to get them all the way down. Very important.
Changed plugs at 59,700 a little short of the 60,000 miles recommended.
Had no idle or acceleration problems with old plugs, new ones run car basically the same. Old plugs look like the pictures posted. Could I have waited another 5-10 k, probably?
Changed plugs at 59,700 a little short of the 60,000 miles recommended.
Had no idle or acceleration problems with old plugs, new ones run car basically the same. Old plugs look like the pictures posted. Could I have waited another 5-10 k, probably?
Probably could have waited another year (depending on your annual mileage), but at least you got this checked off the to do list.
Resurecting this thread.
My V8 W221 has over 180,000 kms, I bought it used and put close to 35,000 myself. Had no idea when spark plugs were replaced, so decided to do it myself. As explained here before, easy and cheap task, plugs cost me about 100$ CAD and only 30 min of work. Before replacement, idle engine sound was "wrhwhrhwrhwhrh" and now it is whisper "hhhhhhhhh". Also, acceleration seems to be a bit better (I am gentle driver anyway) and when accelerating, there is no rumbling noise at low rpm. I checked gap at old plugs, on some of them it was visibly larger than in new ones.
So if your car is lazy, you may consider plug change, even if it turns out it wasn;t the problem, the cost and time involved is realy small
Last edited by Stephen Can; 03-12-2024 at 01:08 PM.
BOSCH USA is essentially a stand alone company. Plugs they sell are always resistor plugs, likely not sourced from Germany
Original poster (eons ago) claims massive improvement ... this is only likely if current plugs are well past replace date or otherwise damaged or fouled.
03-27-2015, 11:39 AM
w221 Spark plugs
Spark Plugs 2010 S-550
