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2005 SLK55 AMG
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1,543 Posts
Discussion Starter · #1 ·
I have done basic servicing on most of my cars from Mini’s, Alvis, Triumphs, Jags and Fords etc but when I acquired the MB I reckoned it was time to hand over these messy jobs to the experts. Basic things like oil change and plugs replacement became clouded with stories of twin sumps, electronic dipsticks, 16 spark plugs and special tools needed to remove just the HT wires! But, thanks to Covid 19, retirement and terminal boredom I swallowed a brave pill and took the plunge. I did the oil change a few months ago so here goes with the plug change on the M113. I dare say some of this applies to other engines.

I wanted to make sure I had ‘everything’ I needed before I started this job including the special ‘spark plug wire removal tool’. I wanted to avoid any potential problems like broken HT leads, fractured or seized plugs and stripping threads. The HT lead removal tool seems very expensive and difficult to buy in the UK and Europe but eventually I found it on Amazon.com from N America. I also ordered a bent spanner on Ebay for a couple of quid and it did in fact turn out to be useful on cyl 1 where you cannot lever against the Cam cover but not much use elsewhere. I have attached a pic of all the tools I used excluding hex keys. I have ¼ 3/8 and ½ inch sockets but found the 3/8 to be the best especially for CYL 8 which has the smallest gap between the firewall panel. I also utilised various extension rods and adapters to achieve the ideal gap between the cam cover and the firewall. My ½ inch torque wrench was too big so I purchased a 3/8 version.

Like I say, Cyl 8 at the rear of the engine was the hardest to access and that was the one I tackled first. To my surprise the boot slipped off without too much persuasion and the others followed with varying degrees to awkwardness. Be careful to pull the boots straight and not at an angle in case the ceramic on the plugs break. This is where the correct tool makes sense. Next I undid the plugs one by one and to my surprise they all came out really easily. I have attached a close up photo which shows what a 40K mile NGK plug looks like.

Replacement was easy reversal. I did a lot of research into replacement plugs. I learned that Iridium is the second hardest metal on Earth and Bosch are ahead of the game on this with their ‘Double Iridium’. In fact, if you click my link you will find they are the recommended option for the SLK55 Double Iridium Spark Plugs | Bosch Auto Parts . Seems to be the best kept secret too since they are considerably less expensive than similar plugs despite being good for about 100k miles! I got mine from Opie Oils for about £107. Lastly, I used plastic ties to hold down the coil pack loom since most of the little plastic tabs have
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broken off the connector plugs. Really not a complicated job which took about three hours including coffees and smokes.

Pics attached
 

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*Premium Member
2007 SLK55 AMG
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748 Posts
Double down on Avel Du comment
I too enjoy doing any of the upkeep on my ride.
Part of the fun in owning it
 

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*Registered
2005 SLK55 AMG
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383 Posts
Fun job right? Nice write up. You even got the official Mercedes spark plug puller! Nice! I also did the job last year and combined it with a compression test on all cilinders. I also had to use some tie wraps because some plastic tabs broke on the wiring loom. I wish I knew they were so fragile. I might have been more carefull with them.

I used compressed air to clean the spark plug cavity before sparkplug removal to remove loose stuff which might accumulate over the years and might fall into the cilinder.
 

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*Premium Member
2005 SLK55 AMG
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1,543 Posts
Discussion Starter · #5 ·
Fun job right? Nice write up. You even got the official Mercedes spark plug puller! Nice! I also did the job last year and combined it with a compression test on all cilinders. I also had to use some tie wraps because some plastic tabs broke on the wiring loom. I wish I knew they were so fragile. I might have been more carefull with them.

I used compressed air to clean the spark plug cavity before sparkplug removal to remove loose stuff which might accumulate over the years and might fall into the cilinder.
Yes, I already broke a couple of clips when I redid the breather cover gasket seals last year! I don't think they're going anywhere with the ties secure. Try as I did, it's virtually impossible to remove the plugs without breaking them.

Didn't do a compression test but I did manage to get the small nozzle of my vacuum cleaner in there to suck out any crud.

Yes, fun job but certainly not worth paying skilled mechy to do the job!
 

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Sold my SLK
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49 Posts
good write up !!
Just completed the spark plugs and cam cover gaskets on mine and the coil clips broke as well .Do you have a photo of how you placed the zip ties on the broken clips ?
 

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*Premium Member
2005 SLK55 AMG
Joined
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1,543 Posts
Discussion Starter · #7 ·
good write up !!
Just completed the spark plugs and cam cover gaskets on mine and the coil clips broke as well .Do you have a photo of how you placed the zip ties on the broken clips ?
Didn't actually put the ties on the clips. Just threaded them thru the original slot on top of each coil pack and strapped the wires down. Since they're so close to the plugs theres little chance of them lifting so it should be fine.
 
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