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Discussion Starter #1 (Edited)
Spark plugs are very easy to change but if you have never done it you may think you can't. Yes you can! It's easy.

Why should you replace your spark plugs?
Spark plugs are one of the most essential components of your car’s engine- old spark plugs can drastically decrease your gas mileage.

Here are directions and pics of my last Spark Plug Change.

1. Make sure your engine is COLD.

2. Have all tools you will need handy.

For this job, you will need:
Hex bit set
Torx socket set or 1/4 socket will do as a last resort.
Rachet wrench
6 or 9 inch extention
5/8 spark plug socket
4 new spark plugs
spark plug gaper if plugs need gaping
Blanket to protect fender from scratches


3. Disconnect battery.


4. Put blanket over fender to protect paint job.


5. Gap your new spark plugs.
You can determine the correct spark plug gap by looking for the engine specifications sticker under your hood. Always get the right spark plugs for your car, preferably the original brand. You can also consult a parts guidebook, or ask for help at the parts store- you will be there anyway to get your plugs and plug gaping gauge.

3 or 4 pronged Spark plugs don't need gaping.





6. Use 5mm Hex bit and remove the 3 screws on the red cover over spark plugs.













7. Lift and Set cover to the side.







8. Here you see the spark plug wire harness.







9. Remove wires from the coil packs.







10. Grab orange plug cap and wiggle it as you pull it off. It may be hard to remove and then set it to the side.







11. Now remove the plug from the other side of the coil packs. I used a flat head screw drive to help pop it off.










12. Now use Torx socket or 1/4 socket and take out the 2 screws holding the coil packs in place.













13. Now use both hands and wiggle and pull on coil pack to remove it. This is a little tough.







14. Now all 4 Spark plugs can be accessed.







15. Using your rachet, extention and 5/8 spark plug socket, take out the the first plug. (I take out 1 plug and put in a new plug before moving on the the next plug. I don't like leaving the spark plug hole open where dust or dirt can fall in.) I used 2 long extentions for the pictures.













16. Remove old plugs...here are mine.







17. Put in new plugs and Hand tighten them, then snug them down with the socket wrench.






18. Follow steps in reverse to put back together. Reconnect battery.

FYI...Make sure when putting wires back on that they are in right location so the plastic wire holder fits into the brackets to hold it in place.









19. Be sure all tools are clear before closing hood.



20. Start car and R):burnout:



SLKman:tu:
 

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Very nice Brent. Wish I was mechanically gifted.
 

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For this job, you will need:

... Torx socket set or 1/4 socket will do.
These are usually called "external TORX®," and use of hex sockets isn't a good idea.

Here's a great set of most external TORX® sockets you'll ever need, i.e. # 77391 here:

http://www.wihatools.com/700seri/773serie.htm



M112 engine owners will need one of these for the inevitable crankshaft position sensor replacement. Probably the V8 (M113), too.
 

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Gap your new spark plugs.
You can determine the correct spark plug gap by looking for the engine specifications sticker under your hood. Always get the right spark plugs for your car, preferably the original brand. You can also consult a parts guidebook, or ask for help at the parts store- you will be there anyway to get your plugs and plug gaping gauge.

3 or 4 pronged Spark plugs don't need gaping.
Longtime German car and motorcycle owners are familiar with the fact Bosch plugs come in the box already gapped to the required value. (It's printed on the box.) This even for conventional single-prong plugs.

I check that kind for fun, but have never had to adjust one. There's really no way to check the platinum and multi-prong versions in any event.

The plugs for V6 and V8 SLKs don't need gapping, either, assuming one uses the original equipment plug (which one should).
 

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SLKMAN, thank you buddy for this amazing post.Y)
This is one of the many reasons I love this forum, thank you for your time of doing this and making this available for other members....
MB dealer would charge you around 200 bucks for this work.....

Brilliant. Thank You, its appreciated alot.
 

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Thanks for the step by step procedure. On early model SLK's - remove the cover and inspect the coil packs hold down bolts. On mine they were standard 10mm hex bolts that did not require the external Torx sockets.
 

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Nice. Don't forget a little anti seize thread compound on those plugs or the next time you do this you might be in for a surprise. :tu:
 

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Update on anti-seize on lugbolts

Todd157K: I've heard conflicting instructions on applying anti-seize material on sparkplugs. On BMW's the recommendation is a drop of oil on the threads with the argument that anti-seize interferes with temperature dissipation from the sparkplug to the engine block. I did however, apply a little dab of anti-seize on the lugbolts - dry, seized lugbolts are the bane on the side of the road.

Revised note: I read from a car repair source and backed up by a fleet auto mechanic to install lugbolts dry, no grease, oil or anti-seize compound on the threads. Application of any of these compounds could alter torque settings up to 25%. A contributor to warped front rotors.
 

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SLK 230 2003 Spark plugs look different...

Hi! I have and SLK 230 2003 US model and after I opened the red spark plug cover here's what I got:


As you can see, mine looks different from yours. Hope it doesn't get things more complicated =)
I went to Bosch website and it gave me this spark plug "Bosch 9603"
instead of F 7 KTCR. The gap on 9603 is 0.044 whereas the manual for MB recommends F 7 KTCR and the gap is said to be 0.039 Will this fit? I read through the Internet and found that the gap for Iridium plugs is a little more than for copper ones due to different design.
Any advice? =)
 

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When I pulled off the spark plugs I saw that they were "NGK IFR6D10" "made in Japan" with the Mercedes Logo on it! I don't know when they were installed. I have no records in the book from the previous owner.
But it seems they've been there for a long time... I think even since factory...

I wonder why does Mercedes use Japan NGK vs. Bosch Iridium? I guess there must be some reasons.
However, since I didn't know what kind I had and the manual called for the copper ones, I decided to go with modern iridium.

So far they work fine. No changes or whatsoever. Will look for MPG.
 

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While I don't have the R170, my advice is to be wary of the Bosch selector web sites. I would go with your owner's manual. I have a pretty good local M-B dealer, and so for an extra $50 I went ahead and bought the plugs from them instead of eBay.

I agree this is an easy DIY - Others also recommend using some electrical contact grease on the plug to coil connection.

Best Wishes.
 

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While I don't have the R170, my advice is to be wary of the Bosch selector web sites. I would go with your owner's manual. I have a pretty good local M-B dealer, and so for an extra $50 I went ahead and bought the plugs from them instead of eBay.

I agree this is an easy DIY - Others also recommend using some electrical contact grease on the plug to coil connection.

Best Wishes.
Yes, I've read about Bosch selector and catalog parts mismatch. I tried to go with owner's manual but after I pulled off the old plugs which were NGK with Mercedes logo on it I wasn't really disappointed =)
These Bosch has the same gap as NGKs and I purchased them in a local store. So far no differences or changes.
I was also reading about the grease and there are different opinions. I just checked the plug wires and plugs but they didn't have any kind of grease on them.:)
 

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Spark plugs are very easy to change but if you have never done it you may think you can't. Yes you can! It's easy.

Why should you replace your spark plugs?
Spark plugs are one of the most essential components of your car’s engine- old spark plugs can drastically decrease your gas mileage.

Here are directions and pics of my last Spark Plug Change.

1. Make sure your engine is COLD.

2. Have all tools you will need handy.

For this job, you will need:
Hex bit set
Torx socket set or 1/4 socket will do as a last resort.
Rachet wrench
6 or 9 inch extention
5/8 spark plug socket
4 new spark plugs
spark plug gaper if plugs need gaping
Blanket to protect fender from scratches
3. Disconnect battery.
4. Put blanket over fender to protect paint job.
5. Gap your new spark plugs.
You can determine the correct spark plug gap by looking for the engine specifications sticker under your hood. Always get the right spark plugs for your car, preferably the original brand. You can also consult a parts guidebook, or ask for help at the parts store- you will be there anyway to get your plugs and plug gaping gauge.
3 or 4 pronged Spark plugs don't need gaping.
6. Use 5mm Hex bit and remove the 3 screws on the red cover over spark plug.
7. Lift and Set cover to the side.
8. Here you see the spark plug wire harness.
9. Remove wires from the coil packs.
10. Grab orange plug cap and wiggle it as you pull it off. It may be hard to remove and then set it to the side.
11. Now remove the plug from the other side of the coil packs. I used a flat head screw drive to help pop it off.
12. Now use Torx socket or 1/4 socket and take out the 2 screws holding the coil packs in place.
13. Now use both hands and wiggle and pull on coil pack to remove it. This is a little tough.
14. Now all 4 Spark plugs can be accessed.
15. Using your rachet, extention and 5/8 spark plug socket, take out the the first plug. (I take out 1 plug and put in a new plug before moving on the the next plug. I don't like leaving the spark plug hole open where dust or dirt can fall in.) I used 2 long extentions for the pictures.
16. Remove old plugs...here are mine.
17. Put in new plugs and Hand tighten them, then snug them down with the socket wrench.
18. Follow steps in reverse to put back together. Reconnect battery.
FYI...Make sure when putting wires back on that they are in right location so the plastic wire holder fits into the brackets to hold it in place.
19. Be sure all tools are clear before closing hood.
20. Start car and R):burnout:
SLKman:tu:
SLkman i would change your valve cover as soon as possible! Your magnesium is corroding away! I did this to mine and when i removed the old one there was a huge chunk of paint that was about to fall down into my engine D: this could've caused me an engine! Yours is really bad, also if you do get one, the gasket don't come with the spark plug gaskets!
 
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