V12TT DIY Coil Pack Replacement - With Pictures - Mercedes-Benz Forum

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post #1 of 6 (permalink) Old 04-13-2011, 12:39 PM Thread Starter
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V12TT DIY Coil Pack Replacement - With Pictures

Disclaimer: Use this “How To” at your own risk. I am not responsible for anything you break (including yourself).

This “How To” covers the driver’s side (cylinders 7-12) coil pack. The procedure for the passenger side (cylinders 1-6) is almost the same. The time to complete a single coil pack change will be between 20-60 minutes depending on your skill level.

This “How To” can also help with spark plug and/or plug insulator replacement.

¼” or 3/8” drive ratchet (required)
¼” or 3/8” drive extension (required)
7mm socket (optional)
Flat screwdriver (required)
5/16” 12 point socket (required – probably actually a metric socket, but 5/16” works just fine)
Torx T20 (required)
Paper towels/rags (optional)
Needle nose pliers (may be required – see Step 5)

Coil pack (required)
Insulators (required if not using a BNIB coil pack)
Spark Plugs (optional – 12 per side)


Step 1 – Remove air box:
First, remove the key from the ignition. You will be working under the hood and don’t want to risk someone else accidentally starting your car with your fingers in there. Then, remove both engine covers by simply pulling upwards on them. With the covers off, remove the three 5/16” 12 pt bolts holding the air box down (yellow circles), unclip the plug (orange circle), remove the hose (yellow circle), then pull the airbox upward gently and toward the firewall to separate it from the intake tube (orange circle). I recommend you plug the turbo inlet with either paper towels, a rag, or something of the like so you don’t drop anything into the turbo (yellow circle).

Step 2 – Remove Intercooler:
To remove the intercooler begin by remove the three 5/16” 12 pt bolts (yellow circles) and loosening the two hose clamps with either a 7mm socket (preferred) or flat screwdriver (orange circles). Then gently wiggle the intercooler up and out of the way, pushing it toward the firewall. Don’t move it too far, as it still has two hoses attached to it. These hoses do not need to be removed to replace the coil pack or spark plugs.

Step 3 – Remove Turbo-to-Intercooler Pipe:
Remove the 5/16” 12 pt bolt and hold down bracket (yellow circle) and pull/wiggle toward the firewall to remove (orange circle). The passenger side of the car is harder than the drivers side on my car, so you may have to use some force.

Step 4 – Remove Coil Pack:
First remove seven 5/16” 12 pt bolts – pay special attention to the location of the two long bolts (yellow circles) and remove the Torx T20 screw on the heat shield (orange circle). Next, remove the plug by prying upwards with a screwdriver. It will come up approximately ½” inch, then pull towards firewall as you keep lifting (yellow circle). Remove the hose from the bracket under the front of the coil pack (orange circle). Now pull the coil pack straight out. It will require quite a bit of force, pull forcefully but not abruptly (especially if you are just doing an insulator or spark plug change). Pay special attention to the wires are you try to remove the coil pack (orange circle). The coil pack will come out without removing anything else, but you will have to take care as you try to remove it.

Step 5 – Remove Insulators/Spark Plugs (if required):
Once you have the coil pack removed, there may still be some red insulators left on the spark plugs. To remove them, use needle nose pliers. If you are replacing with a new coil pack (that comes with new insulators) you will not need to be as careful. If you are not replacing your insulators – use care with these. Note: I am told that old/cracked insulators can give the same codes as a bad coil pack. These insulators are available separately. If they are bad, when you squeeze them they will look cracked/dry rotted. If they are still soft and pliable with no cracks, they are probably not the problem. If you are going to replace your spark plugs, now is the time!

Sorry, I forgot to take pictures of this part – but it’s very straightforward.

Step 6 – Reassemble:
Basically repeat Steps 1-5 in reverse order. A few notes:
1) When you install the coil pack, give firm pressure to seat it; but do not push too hard or you may break it. You can also get it started and use the bolts to help finish seating it. Pushing down directly over a tube is better than pushing between them. And remember where your two long bolts go.
2) Don’t forget to put the heat shield on the new coil pack.
3) Take care with the wires attached to the plug.
4) When you put the turbo-to-intercooler pipe back on, do not tighten the bracket all the way until you have the intercooler reattached and bolted down; otherwise you may put it in a bind.
5) Do not over tighten the bolts when you reassemble – you are putting bolts in fine threaded aluminum and you can strip it.
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post #2 of 6 (permalink) Old 05-23-2011, 03:23 AM
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These are really useful steps. Thanks!
post #3 of 6 (permalink) Old 02-27-2012, 09:01 PM
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thnk you this is really helpful..
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post #4 of 6 (permalink) Old 04-10-2012, 10:52 PM
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Question thank you

Great tutorial!!!

Do you happen to know if they have upgraded or improved the coil packs over the years of the V-12 production, say 2005 - on?

It appears to be a great weakness in an otherwise bulletproof engine.....besides the intercooler issues, etc....

Thanks for any info in advance.......

Current rides:

2005 Silver/black Mercedes Benz SL 65 AMG
1995 White/tan/blue top Porsche 911 Cab - 993
2011 Blizzard White/Sand Beige Prius 5

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post #5 of 6 (permalink) Old 04-23-2012, 09:16 AM
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Is all this in reference go ignition coils ?

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post #6 of 6 (permalink) Old 06-04-2012, 07:15 PM
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