You may need to remove the Spark Plugs from your DB9 to replace them at a scheduled service interval or as part of some other service procedure (like doing a compression test or removing the valve cover, etc.).  This is a fairly simple procedure once you have all the preliminaries out of the way, but there are a few  small tricks to it I will share with you below.I’ve done a ton of work already to get to the point where I can remove the spark plugs.  You can check out my other posts and videos on:

• Depressurizing your fuel system
• Disconnecting your Battery
• Covering your fenders
• Removing the Engine Bay Cross Braces
• Removing the Intake Manifold Brace
• Disconnecting the Fuel Rails and removing the Fuel Injectors
• Disconnecting all the other ancillary components attached to the manifolds
• Removing the Intake Manifolds
• Removing the Spark Plug Covers
• Removing the Coil Packs

Tools Required

You only need a few things:

• 5/8″ Spark Plug Socket (3/8″ drive)
• Ratchet (3/8″ drive)
• 6″ extension (3/8″ drive)
• Two (2) 3″ long extensions (3/8″ drive).  Note: Using a single 6″ extension won’t work for the rearmost cylinders, you need the two 3″ ones.
• Small inspection light
• Cardboard tray to keep track of which plug came out of which cylinder (we made this back in the section on removing the fuel injectors)

Procedure

If you have all the preliminaries noted above already out of the way this step only takes about 5 minutes per side.  Easy.

The official Aston Martin Workshop manual section on Spark Plugs covers it in steps 5 “Remove the Spark Plugs”.  Succinct.  The schematic in the diagram doesn’t even show the valve cover being installed (no, you don’t need to remove the valve cover).  Here’s my slightly more verbose version with a few tips:

• Probably the most important step in the process isn’t documented in the Workshop manual.  I have read several forum posts from people who have discovered the Spark Plug recess (well) is filled with engine oil when they finally get a look at the Spark Plug.  This occurs when the valve cover gasket leaks and lets oil build up in the well.   This matters to you since you are about to remove the spark plug, and this will essentially open a drain hole in the bottom of the well allowing all the accumulated oil to flow right into your cylinder.  NOT good.  So, this step is to take your inspection light and peer down into each well and see if you have an oil puddle.  If so, you’ll need to invent some method to mop it out before pulling the plug, and of course you also now need to worry about fixing the oil leak.
• Remove each spark plug using the 5/8″ spark plug socket.  Since they are at the bottom of the well, you will need about 6″ of extensions to reach them and to have clearance to turn the ratchet.
  • Tip:  On most of the cylinders I could use a single 6″ extension with a 3″ extension for added clearance.  But, on the rear most cylinders that are under the cowl with restricted clearance above them, I had to use two (2) three inch extensions and follow this trick.  There is only about 3″ of clearance above the well’s opening, so I slipped the spark plug socket part way into the well first, then held it with one hand and attached the first of the 3″ extensions and lowered them a bit until I could then attach the second 3″ extension.  Then I lowered that onto the spark plug and finally attached the ratchet.  Check the video out below to see this in action.
  • Tip:  They will be pretty tight and take a fair bit of torque to get loose.  You need to be careful to not cock the socket over sideways while doing this else you risk breaking the porcelain insulator.   This wouldn’t be the end of the world, but you certainly would need to replace the spark plug and have to deal with the broken insulator stuck in your socket, and the potential that your socket wouldn’t be able to lift the threaded base up and out of the well.
• Place each removed spark plug into your cardboard holder to keep track of which cylinder they came from.  Even if you plan on replacing them all you should probably take the time to inspect the condition of each plug tip to see if you have some other engine issue going on (wet and oily, sooty, broken, etc.).

  

• Be careful not to drop crap down the open spark plug holes since it goes right into the cylinders.  You don’t want to screw up a $30,000 engine.

That’s it!    With all your plugs removed you can get on with the next phases of your project, and hopefully that’s starting to put new bits back in and getting your DB9 back on the road in tip top condition.  I’ve been doing this as part of curing my lumpy idle situation (check out my post on this), and this was the final dismantling step, and I am looking forward to starting to put the car back together again with the new bits!

Check out this short video on the process I used: