From the "other board"
Thanks for the update. Good info to know. Another person had reported a similar situation but it wasn’t clear. Your experience seems definitive.
I’m not surprised BMW updated the code. As we had explained from our first letter to BMW we expected the idle problem was created by the DME. The DME software is not reacting well to the vanos failure and creating the idle symptoms. As I’ve explained in other posts, I expect that BMW knew of the vanos failure during testing of the M52TU engine (99-00). Instead of addressing the vanos hardware problem they elected to modify the DME software so that it acts “normally” to the vanos failure. As we know the DME shows no indication of vanos failure and does not set OBDII fault codes. The vanos failure was likely encountered in mid testing when the engines had 40k+ miles on them. Software mods were likely made to most of the software but they missed a unique spot in the code where the vanos is used in an unusual application. This is the cold weather cold start situation when the vanos is used to help heat up the cats faster. Subsequent to manufacturing the M52TU, BMW likely became aware of the “missed” location in the software where the code was not “messaged”. By the release of the M54 engine BMW had this section modified likely like the rest of the software to act “normally” to the vanos failure. So it’s no surprise that they would go back to the M52TU engine code base and update it with the same patch.
Instead of addressing the vanos hardware failure BMW elected to incorporate “software workarounds” to smooth over the problem and hide its existence.
I do not have the facts to prove that BMW found the problem during M5TU testing and modified the software to act “normally” to the failure, but all indications seem to point to this.
With regard to improved gas consumption with the updated M52TU code base, BMW might have been able to modify the software to better function under the vanos failure and achieve better gas consumption.
The double vanos provides many great benefits: improved, power, torque, gas consumption, emissions, etc. A software fix might be able to keep the engine from faltering and throwing codes, but it can’t make the vanos overcome its hardware failure and perform properly. A software fix can not provide the improvement in power, torque, gas consumption, that a properly functioning vanos provides.
Here’s something an owner recently wrote me after replacing his vanos, “Wanted to follow up and report that "yes" the car does feel quite a bit faster. Definitely more of a "pull" than before.”
The true solution to this problem is a hardware fix to the vanos. We have sincerely attempted to work with BMW to address this matter. But after they strung us along for almost a year they finally came out with a clear position: “No further development will be done”, ie the problem will not be addressed. This has unfortunately been their consistent position since the very beginning when they discovered the problem.
BMW is continuing to sell replacement vanoses with the same failing piston seals. We purchased a new vanos and had the piston inner O-rings tested for material makeup. We found that they are made of Buna. Buna is a very common material used in O-rings. Unfortunately it is limited in temperature and chemical resistance characteristics. Thus we are not surprised that it has faired so badly in the vanos. Upon inspection we have found the Buna O-rings to flatten at their top and bottom surfaces, shrink in size, and plasticize thus loosing their elasticity. The outcome of this is the loss of support for the Teflon outer seals and thus the loss of the Teflon seals’ ability to sustain a seal with the vanos cylinder walls. This all causes failure of the vanos function.
I was hoping that the vanos failure would show up in emissions testing but for whatever reasons, and this can be speculated upon, this has not been the case. Thus I don’t believe we can convince the government to force BMW to address the problem.
Therefore as a last resort we are going down the path of reverse engineering the design and producing better seals. We are very fortunate to have a seals expert working on this effort for us, Tony540. We have talked to many seals experts and manufacturers and they have consistently recommended that we use Viton as an O-ring material for this application. Viton has much better temperature and chemical resistance characteristics than Buna. A main complication to replacing the O-ring is the Teflon outer seals. These will be damaged when removed from the piston seals grove, thus new ones will be needed. The vanos Teflon seals are unique in dimension and thus need to be custom manufactured. Teflon seals also require special tools for installation. They can not simply be stretched and mounted like O-rings. Thus we are working with a seals company to manufacture the Teflon seals and Viton O-rings. We will also be working with a company to manufacture installation tools especially made for the vanos piston and Teflon seals.
We are waiting on a first small batch of the seals, which we’ll be receiving very shortly. We (Tony540) will install them with custom built tools and test for proper fitment. We (Tony540) have made very careful measurements of the vanos and seals and have worked closely with our seals manufacturer to ensure proper dimensions for the seals they’ll be manufacturing. Once the fitment is verified, I’ll be installing them on my car. I’ll be performing before and after performance tests. If all goes well I suspect I’ll look for a few owners to perform the repair on their cars and providing feedback. Again if all goes well, we’ll be ordering the seals and tools in larger number so we can begin to distribute them to others. The performance tests of the car with the new seals will be an indication of the function of the vanos in “real time”. I might have to purchase one more new vanos from BMW and perform the performance testing on it just to prove the redesigned seals provide the same performance as a new BMW vanos. I plan on finding owners that will allow for the replacement of their seals after a specified period. This will allow for inspection of seals at set periods of miles. I’m currently thinking of 20, 40, 60, 80, and 100k mile inspections.
I’m putting together a thorough writeup on the complete repair procedure. I’m also creating a website to facilitate the purchase of the seals/tools and access to the repair writeup and other relevant information. I’m still working out the costs of the items but am trying my best to keep the costs down. The cost of the seals and tools will be a fraction of the cost of a new BMW vanos.
I hope much of this will be ironed out in the next three months. Much of this effort has been slow coming in this past year, but things are moving faster these days. I’m now practically working full time on this effort, and Tony540 has been extremely generous with his time and effort.
Well, I’ve gone on a bit. I surely don’t mean all this as a response to Stephen. I’m just trying to provide insight to others reading this post and give an update on our efforts to address this problem.
Stephen, thank you for the post.
528i 5sp 06/00