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  1. #1
    Newby
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    Carbon Build Up

    Carbon Build Up I am new to this forum. I am seriously considering the purchase of an 03 M5. I have seen postings re: carbon build up. Is this unique to the M5 (as compared to and E39)? Is a low mileage (garage queen) M5 more likely to suffer this condition versus an higher mileage vehicle? Is a certain type of driving more conducive to causing this build up? Why is it so expensive to fix?


  2. #2
    hdclown
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    There are some very long threads on m5board.com

    I suggest you hop over there and read them.

  3. #3
    Panos
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    Jsut get on the car for a while and that should

    clear it out. Driving an M5 as if it were a 520i will cause this. Someone who babied the throttle around the city its whole life may have these issues. I doubt youll see it on the M5 some ex-formula driver owned.

    Panos
    99 540i.6

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    not true, with regards to the secondary smog ports

    The main 'carbon blockage' issue is in the smog pump's secondary air injection lines, up to and into the heads. That is what gets clogged and sets off a service engine soon light. Has little, if anything to do with driving aggressively. A search on m5board.com will give a lot more detail.
    Mike

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    from what ive read...

    There are two seperate issues that involve carbon buildup:

    The first and more rare one is carbon build up in the exhaust valves and manifolds. This can be avoided by driving the car how it was intended and warming it up properly (dont let it idle) so that gaskets are doing there job and not allowing oil to get where its not supposed to be. Running the car for a good period of time at high rpms (65mph/3rd gear/15min) helps if use of higher rpm range is not common.

    The second is carbon build up in the secondary air channels as you mentioned. I have actually never heard of this before but after reading up and looking at some engine diagrams this could be easily solved by replacing those channels. They are inexpensive and external to the engine so it is not a labor intensive job.

    M cars are made to be driven a certain way. You can baby it occasionaly when your taking your mother somewhere but you should let the engine wind up often. Otherwise buy a nice loaded 530i and coast comfortablly around town with an extra $20k-30k in your pocket.

    Panos
    99 540i.6

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    according to the dealers charging $6-8k....

    it is a labor intensive job to clean out the secondary air passages. Sure there are some external parts, but there are also passages inside of the heads. The official bmw fix involves removing the heads, cleaning out the passages and then boring them to a larger diameter, presumbably to prevent recurrance. One guy on the M5 board replaced the external parts only to find solid carbon in the passages in the head that he could not remove with solvent and brushes, as you (and I) would expect. There is a big poll on the m5board about this, and it does seem to be related to oil consumption, somewhat. I drive my car hard whenever i can, that's why i have an m5, vs a 528, but i do not think that makes it immune to the problem (with regards to the secondary air pump system). Fortunately, it's just a smog system, so if it fails, and you can live with an SES light, it causes no harm. If you're in a state like mine, (ca.) where you have to pass a smog check, you have a problem!

    for a lot of info, go to www.m5board.com and you'll find a few large threads about this.
    Mike
    00 M5

  7. #7
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    Re: Carbon Build Up

    Carbon build-up problem: FACTS

    As mentioned by the other poster, please visit the M5board.com for complete discussion of this isue (in particular, the thread titled: "FAQ on the Carbon..." (search if you don't see it on the opening page of new posts).

    Here is the carbon issue in a nutshell:
    - Secondary air flow fault triggers the Service Engine Soon light
    - The "secondary air flow" is the cold-start emission system; basically this is an air pump which pumps air into the exhaust just downstream from the exhaust port during cold starts. (The pump shuts off after a certain temperature is reached.)
    - The carbon clogging can completely occlude the aluminum feeder tubes from the air pump to the engine heads. It is not clear to what extent carbon in the heads themselves can trigger the fault, but BMW's 'solution' is to pull the heads and clean them of carbon, a very labor-intensive procedure. No doubt they also replace the secondary air tubes (rather than clean them).
    - It is not clear why carbon deposits are so heavy in this system; the system has a shut-off valve which presumably keeps carbon-rich exhaust gases from entering the system while the pump is turned off.
    - This issue has no impact on the car's performance. It ONLY impacts the efficacy of the cold-start emission system.
    - Currently the ONLY way to get the SES light turned off is to have the $8,000 cleaning procedure performed. It is so expensive because of all the labor involved in pulling the heads and manually cleaning the hard carbon deposits.
    - This issue has NOT officially been covered under warranty because it does not represent a 'failure' per se (ie, a broken part), but rather is due to 'deposits'. (Obviously the system IS broken if failure occurs prematurely under normal usage!)
    - Although non-US cars have the same secondary air system, the carbon issue does NOT appear to affect non-US cars. This is probably because the DMEs in non-US are not programmed to monitor secondary air flow (perhaps due to lower emissions standards outside the US).
    - Federal emissions warranty ala the Federal Clean Air Act, madates that manufacturers cover the cost of emission system repairs for up to 80,000 miles unless the manufacturer can demonstrate that the failure is due to improper owner maintenance.
    - After 80,000 miles, owners paying for the head-cleaning procedure are essentially paying $8,000 to maintain a cold start emissions system, which is ludicrous. Normally state-specific emissions requirements limit owner liabilty for emission system repairs to some reasonable figure ($450 in CA). Most states don't even have cold-start emissions testing.
    - We hope that with organized action, it is reasonable to expect BMWNA to start covering the cold start emission system up to 80,000 miles under warranty, and to work with owners >80,000 miles, possibly to include disabling the air monitoring of a confirmed 'dead' system, since maintenance of this system is no longer required by either the manufacturer OR the owner.
    - Thus far, we have confirmed cases with '00 and '01's. We have one case with the problem occuring at only 17,000 miles ('01 MY), but most problems occur with higher mileage (generally over 50,000 miles).
    - This issue is NOT related to driving habits from the data that we have. This issue MAY be exacerbated by higher oil consuming cars, although we have seen the problem with cars that consume very little oil.
    - We suspect as the mileage piles up on '01-03 model years, the carbon problem will affect these cars in greater numbers. It may well be that it will eventually affect most or all cars with sufficient mileage.

    Hope this answers all your questions!

    Best regards,
    Dave

  8. #8
    chaz
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    Re: Carbon Build Up

    Dave,

    any further insight into this issue? I have a 02 m5 with 63k and am being told by dealer possibility of head cleaning or replacement.

    thanks,

    chas.

  9. #9
    redrocket-wi
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    Re: Carbon Build Up Fix

    Powerchips of california can reprogram your ECU to not recognize the fault. You also get fuel octane optimazation which results in about a 10HP gain or so they claim. I just had mine done & the SES light has not come back on. Fix costs $990 or $890 with M5 board referral. Their customer service has been fantastic.

    Ask for Travis & tell him that I referred you (Mike H. from Wisconsin)

    good luck

    www.powerchipgroup.com

    Mike
    [email protected]

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