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test test D3 A8/S8 (2004 - 2010)
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  • 4.2 Air Filter Change Procedure....
    Posted by: Audis or VWs 4Life (817) on 2009-07-22 21:20:35

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    Folks, those of you with 30k or more miles who haven't changed your air filter or are unsure of your air filters age, I would highly recommend changing them as soon possible. Its completely DIY on the scale of 1 to 10 where a ten is trannie rebuild, I would list this as a 1.

    Again do all this work at your own risk I take no responsibility for anything that may go wrong in your situation.

    Its 5 screws on the airbox and two on the MAF. The bottom screw is a real PIA unless you have the right tools.

    Required tools are Philips head screw driver, with an extra long shank (10-12") and a power screw driver with the ability to handle a tight 90 degree turn. Alternatively an extra short shank short handle Philips head could work. A good source of light would be advised too as a few of these screws are pretty deep.

    Undo the first 5 screws on the airbox.


    Note the 5 screws on the airbox won't come out. They are held in by the plastic case so don't worry about loosing them in the bottom of the engine bay. Just get them loose enough maybe a dozen turns. The long shank screw driver is a must have unless you have hands small enough to get between the headlight housing and the airbox. That screw is down pretty deep.

    Then undo the two screws on the MAF. The top one is cake. This screw comes all the way out so be careful and keep your fingers on it.



    The bottom screw not so much.
    There are a lot of hoses in the way, its even hard to photograph.


    This is where the power screw driver that can do 90 degree turns or a very small shank philips helps.

    I put a little tape on my power screw driver to keep the bit from falling out.


    Gently pull the airbox cover directly upward. Pull strait up and you'll see that the flex hose at the front has guides that force the airbox cover up in a very direct manner. Gently move the MAF aside, the pipes are slightly couple and little bit of movement is okay to separate them. Try not to put any pressure on MAF's honey comb plastic grill. These can be fragile.

    Replace the air filter element with either a stock replacement part or an aftermarket OEM. I used a Hengst air filter. It actually looks better then stock double the folds in the filter element its self.

    Here is what my old filter looked like....

    Can you say YUCK!


    Vacuum out any debris at the bottom of the airbox, insert the filter element on the plastic ring and gently guide the airbox lid back into place. Make sure you light it up with the flex hose. As you're dropping back the box top, reinsert the MAF. Get it all snapped back into place, and then start screwing back the top of the MAF to the airbox. Don't tighten it down until you get the bottom screw mid way or slightly tightened as well. Then tighten both screws up, and tighten up your 5 airbox screws.

    Start your car up, drop the hood and enjoy the extra ponies that managed to escape in the past several thousand miles.
    • Darn Germans...
      Posted by: Biggus Blockus (3783) on 2009-07-28 18:11:51

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      Why not put 2 latches on the cover insted of a bunch of screws?

      A $70,000 price tag should yield a car at lt least easy to service as a Chebby (for the routine stuff).

      A clean air filter is critical for engine performance and economy and it should be easy to check.

      /rant


      PS - I still love my Audi!
    • I think it's even easier in the D2s. I run a K&N with no problems - a good reminder to check it.
      Posted by: jazbo123 (1515) on 2009-07-23 08:39:11

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      I'll be under and over the car this weekend anyway checking for my elusive suspension noise.
      • K&N is a good way to screw up the MAF. OEM filter filters better
        Posted by: Kneale Brownson (5558) on 2009-07-23 08:49:07

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        • A majority of the people who screwed up their MAF put too much oil on the filters.
          Posted by: Push That Tush (666) on 2009-07-23 15:58:57

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          I've used K&N with about every vehicle I have owned and my family's with no problem.
          • I know how to oil them and...
            Posted by: MP4.2+6.0 (4369) on 2009-07-23 20:55:18

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            I tested it across two MAF's on a 4.2 C5, where one was new and one had been used with a K&N for maybe 30K miles. Cost 10%+ on measured peak airflow for what the MAF saw, which translates to HP LOSS. The telltale red oil dye down the intake tract was the give away--it was a very light mist film to be clear accumulated over several tens of thousands of miles, not oil run off type stuff. Virtually ANY oil on the MAF filament wire and it's toast as far as accuracy. I have tried both spray and bottle type application, and putting it on very light and still letting any excess run down/off overnight or longer. And, cleaning with rubbing alcohol or electro type cleaners doesn't bring it all the way back either.

            They did work okay seemingly on a 2.8 C4 and on a pre MAF C3 with CIS-E, but definitely bad news on a C5 4.2, using actual measured airflow calcs with VAG COM in a back to back swap out of the MAF and all other parts constant.

            Factoring in the MAF damage risk and expensive part (and it's often insidious since it affects airflow just marginally, not catasprophically), going to a 15K air filter change, or even just blowing it clean at each oild change, is more cost effective and risk free. The good German filters also often have more pleats if you get technical about flow capability, and if you really look at the car hard, you may conclude the air inlet to the filter box is the bottleneck; it pretty much is obvious on the C5 anyway, where the then 4.2 S6 variant used a stock box and filter but an air bypass valve and different manifold (unclear if cam was any hotter from the specs). The known changes suggest where the real flow problems are on the 4.2, at least on the pre FSI ones. If you have the round type filter on the D3, I would say even less likely it is the bottleneck since they went to that relative to the older panel ones to up the flow (and capture area) yet somewhat more.
    • this would be a good time for a K@N
      Posted by: Lord of the rings (4004) on 2009-07-10 03:13:10

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    • Why not just unplug the MAF?
      Posted by: rkwA8 (1855) on 2009-07-22 22:52:07

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