Changing the Air Filters is a standard service item for any car on the road today, but on your DB9 it is a pain in the ass.  In any normal car they’ve design the air filter system to be easy to service, but oh-no, not Aston Martin.  All those good looks come at a price, and in this case it meant they had to stuff the air filters in behind the front bumper, never to be seen.  Changing them is part of the 2 year annual service regime, so you should get to know how to do this properly, and I’ll share what I know with you below.

Parts

There are only a couple of parts you’ll need.

• Air Filters – Aston Martin p/n 4G43-9601-AB-PK.  This contains the two (2) air filters you’ll need.   You can get these for about $123.72 USD online here, or you can get them a little cheaper by contacting the great Parts Team at HWM England (let them know you heard about them from Aston1936.com and they’ll give you some special pricing).

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  Air Filter Housing Gasket (optional) – Aston Martin p/n 4G43-9C664-AB.  You will need quantity two (2). This is a 42 inch long rope like gasket that would be used to replace your original one in the Airbox housing cover if it’s perished.   Available online for about $4.71 USD, or a little cheaper from the Parts Team at HWM.

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Tools Required

Only a couple of tools are needed:

• 8mm 6-point socket
• T25 Torx bit
• 3″ Extension
• Ratchet or Speed Driver
• Torque Wrench capable of 2 Nm (this is a very low setting)
• Optional (if you are replacing your airbox cover gaskets)
  • Small flat blade screwdriver
  • Small pair of side cutters or scissors
    

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Procedure

Swapping the filters themselves is easy (a 10 minute task), but there is a good deal of preparation work to tackle first.   I’ve done posts and video’s on all the steps:

• Preparing a road wheel for removal
• Single point jacking of the car
• Putting the car on jack stands (optional since you can do one side at a time)
• Removing the front under tray (they say this is optional, but if you are in the middle of a full service you’ll have this off anyways)
• Removing the front inner wheel arch plastic fender liner (they say you can just remove a few screws and bend it back, but I’d rather remove it all).

 

After the liner is removed, you can find the air box at the bottom of the wheel well in front of the road wheel.

Once you finally have access to the air box, it’s actually pretty simple:

• Crawl underneath and remove the seven (7) bolts that hold the air box cover using your T25 Torx bit or 8mm socket.
• Once the screws are removed, separate the airbox cover from the air box.
  • I had to give it a few ‘thumps’ with my hand to break it loose.
• With the cover off you’ll finally see the air filter.  Grip the filter and wiggle it while pulling it down.  It should come free with just a modest amount of effort – no tools required.  Check out my video below.

With the filter now out, have a look at the bottom of the inside of the filter for a build up of engine oil.  If you are finding a wet puddle of oil, you may have a classic DB9 issue with failing PCV valves that are allowing oil to be entrained into the crankcase ventilation, which flows back to the air inlet pipe on the front of the throttle bodies, and then it will drool back down the air inlet pipe and down into the bottom of the air filter.  To learn more about what’s going on check out my other articles on the PCV system and how to change the PCV Valves [spoiler alert – it’s really hard].

I took the time to do a few things to the air box cover while it was off:

• I shook out the debris accumulated in the bottom (leaves and bugs).
• I checked that the white plastic button/valve was free to move (and rattle).  I think this is a water drain.
• I wiped down the surfaces to make it look nice.
• I checked that the groove around the edge was clear of debris.

[Optional] When you are cleaning the groove around the airbox cover, this is the time to check the condition of the airbox cover gasket.  Its embedded in the groove.  It needs to still be resilient, and sit a little proud of the plastic groove so it will smush up and seal against the other part of the airbox when you put it back together.  If its stiff and squashed flat/flush – its probably been baked and its time to replace.

• Along the long edge of the airbox you should see the small gap where the old gasket ends meet.  Use your small flat blade screwdriver and dig one of the ends up carefully, then just pull the whole gasket out of the groove.
• Install your new gasket by carefully tucking the end into the groove with your flat blade screwdriver, and then work your way all the around with the screwdriver bit-by-bit tucking it down.  Slow and tedious, but only takes a few minutes.
• The new gasket is longer than needed, so when you come to the end, you’ll need to use your side cutters/snippers to snip off the excess length (probably about an inch as seen in my video below).  Tuck the last bit in and you are done swapping the gasket!

Now it’s time to fit the new air filter.   Installation is pretty much reversal of removal process.

• Holding the air filter firmly, I pressed up and wiggled it to fit it back on the mount.
• Refit the air box cover, paying special attention that the groove around the edge mated properly with the rest of the air box.
  • Be really sure it is it fitted properly over the curved airbox inlet pipe.
• Reinstalled the seven screws using your T25 bit or 8mm socket.
  • Fit them loosely until you have them all started, then use the speed driver to just snug them all up evenly.  Don’t over tighten these, you are screwing into plastic.
  • Use your torque wrench and torque them to the official Aston Martin torque spec of 2.0 Nm.  If you don’t have a torque wrench that adjusts that low, just make them evenly snug.

That’s it!   Now you can either carry on with the rest of your service, or set about reinstalling the fender liner, front under tray, road wheel and putting the car back on the ground.  Don’t forget to properly torque the wheel nuts.

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Video

I made an action packed video of the process you can watch here: