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How to stop MAF oil contamination (CLK 230K - W208)

Discussion in 'DIY: Engine, Drivetrain, Fuel and Exhaust' started by jamesmc, Dec 9, 2007.

  1. jamesmc

    jamesmc Senior Member

    Likes Received:
    Jul 23, 2007
    Algarve, Portugal.
    Your Mercedes:
    W208 CLK230K Cabriolet
    It is believed that the info also applies to all W202 (C class) Kompressor engines.

    History behind this.
    There have been a few discussions in the Forum about MAF failure on the W208. This post covers the failure of the MAF - by oil contamination.

    If your W208K has a mileage in excess of 90,00 miles
    This is one job that you should carry out in the near future as a matter of preventive maintenance.
    In excess of the above mileage even if your car is not suffering from this problem now it will, which is exactly why I did the job anyway.
    The parts are cheap in comparison to replacing dead MAF sensors.
    If you cannot do the job yourself approximately 4 hours labour should be allowed for a workshop to complete the job.

    One Forum Member carried out a lot of research on the problem and, along the way, dispelled one particular myth quoted a few times in the past :

    If your W208 (W202) has oil in the Air filter housing or any pipework leading, via the intercooler, to the MAF
    then it will not be Kompressor (Supercharger) related failure causing the problem.

    The reason for this (as pointed out byjiminessex) is that, unlike a turbocharger, there is no oil feed from the engine to the Kompressor. The only oil the supercharger uses is held in a tiny inbuilt reservoir within the compressor body itself. This quantity of oil alone is insufficient to cause oil contamination to the point where it reach the MAF.

    So, if it isn't a Kompressor (Supercharger) fault what causes the MAF oil contamination problem?
    The research by jiminessex answers that:
    The idle to upper partload oil breather system is blocked and forcing the highload oil breather system to accept the excess oil residue at low airflows.
    The excess oil is then being dumped into the air filter housing then travels via the intercooler and associated pipework to the MAF.
    The MAF dies!

    The DIY repair. as carried out by jamesmc

    Parts to be ordered prior to the work:-
    1 x Main hose - MA111 018 15 82
    1 x Valve/Tee-Piece complete - MA111 010 00 91
    2 x Small bore hoses - MA 002 094 01 82 (supplied to me as one double length hose that I chopped in half)
    2 x Nozzles - MA111 017 00 12 (These are brass)
    1 Set (pair) of inlet manifold gaskets. Sorry no part numbers. These are more like silicone 'O' ring material rather than traditional flat manifold gaskets.

    Tools required
    A good DIY mechanics toolbox with Metric socket set will cover most of the work
    Plus: Torque Wrench & Reverse Torx Sockets (for fuel rail/manifold bolts)

    The Job
    I haven't gone over every finite detail here but it stands to reason that any cables/connectors that hamper access along the way need to be disconnected.

    • Disconnect any necessary pipework... fuel lines etc. from the fuel rail.
    • Remove all the inlet manifold bolts including the two extended reverse torx bolts which, as well as securing the fuel rail, also act as manifold securing bolts.
    • Ease the fuel rail out of the way
    • Ease the manifold off and away from the head to one side, but don't remove it completely.
      Pulling the manifold away from the head and to one side a little gave me enough access to do what was needed. I suspended the bulk of the weight from the bonnet using bungees so that (in effect) it was floating, almost weightless, to one side.
    • Remove the two small bore hoses along with the 'T' piece and the main hose.
      Both of the small bore hoses (MA 002 094 01 82), which connect to the underside of the nozzles (MA111 017 00 12), were brittle as mentioned earlier in this thread, hence the need to ensure you have all the parts required before getting stuck into this job.
    The brittle small bore hoses simply snapped off with very little effort.
    Look in the images below and you will see the original small bore hoses fitted with the 'T' piece in place

    • With a pair of small light duty side cutters snip off the rest of the brittle hose remaining on the underside of the nozzle tube connectors.

    On inspection, and with a squirt of WD40 via a small tube up the disconnect nozzles, I noted that the forward brass breather nozzle was about 90% clogged and the rear nozzle 100%. So not a lot of breathing going on there!

    This is the forward brass nozzle that was about 90% blocked
    You can also see the original small bore hoses and 'T' Piece in place

    Another shot of the forward brass nozzle that was about 90% blocked
    also showing the original small bore hoses and 'T' Piece in place before removal

    Looking directky from above at the rear brass nozzle that was 100% blocked

    After inspecting the existing nozzles, even though I had two new replacements, I decided to leave them in situ. In my mind that was the safer option rather than trying to extract brass from aluminium that had resided (mated in that position) since they left the factory in 1999.

    • Check the bore size of the new nozzles and select a drill bit that matches the bore size.
    • Clean the existing nozzles out in situ using a small drill bit held by hand only. I also used tooth picks and WD40 to flush out the debris. End result? Two clear nozzles to original spec.

    The Valve 'T' Piece (MA111 010 00 91) looked a bit choked up too when I investigated further. It could be cleaned I guess but the cost of a new one is minimal.

    • Replace the inlet manifold gaskets with two new ones and reassemble.
    • Intake Manifold Bolts are torqued to 20Nm as recommended by MB.


    Extra DIY pointers: How to Clean your MAF by Parrot of Doom

    For further reading check out thread Oil In Air Intake thread
    Jeffthenorm likes this.
  2. jimsinessex

    jimsinessex Senior Member

    Likes Received:
    Aug 4, 2003
    Your Mercedes:
    2008 W209 CLK 320CDI Coupe

    As a follow up I would add that I have now covered another 55,000 miles since replacing the breather system under the inlet manifold without a single misfire or MAF problem.

    Dogfish likes this.
  3. Blobcat

    Blobcat Moderator

    Likes Received:
    Feb 8, 2006
    Near Grange Moor (not Wakefield...)
    Your Mercedes:
    R171 SLK280 3.0, Land Rover 110 County SW
    If you wish to discuss this thread pls post replies here

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