FAQ on Carbon Build-Up Issue (First Attempt) - Page 54

Laidback · 12th March 2006, 05:29

Quote:

Originally Posted by tmlesko

Dave, first, thanks for all your work on this issue! Second, I am one of the people who cleaned the pipe, head ports and changed the valve myself. After clearing the codes, my light stayed off for several months. approx. 3000 mi. after that. I then used some valve and fuel injection cleaner, first the German brand, the light stayed off. I now am using Chevron Techron, the larger bottle for 20 gal. of fuel. I use this every third tank of fuel. I have not had the light come back on for 4000 mi. I also had pre-cat O2 sensor faults that seem to have gone away.

Here is a picture of my pipe and valve. The valve was not rusted, just had "some" carbon build-up. the pipe had about 1/8" of carbon all around, not closed up by any means. I did clean out the head ports, but access is limited to only an inch or so into the head. I cleaned the pipe and replaced the valve as noted in a previous post (page 6, #204)

Thanks again for all your work on this with BMWNA.

Tom L.

is it ok to use fuel system cleaner? which is better chevron or redline si-1 fuel sys. cleaner or the redline lead sustitute has anyone used this products before? just curious on the effects of using fuel system cleaner...

tmlesko · 12th March 2006, 17:30

Quote:

Originally Posted by wilsodh

Tom,
Thanks a lot for the update and comments. Looks like I was mistaken about no DYI or tube-cleaning success stories!

And thanks for the photo... it is interesting to see all that carbon building up in the tube. One wonders why it is there. What are your thoughts about routinely swapping in new shut off valves as a preventative measure. How demanding would this job be?

Dave

That would be failry easy to do since it is on top of the crossover pipe (picture below). I don't know how much that would help though, it doesn't seem to be the culpret. I thought about dis-mounting the valve off of the crossover pipe and blocking the mounting hole on the pipe, then fastening the valve to the pipe (so it is not dangling) and let it blow air into the engine bay. Seems like this would tell the computer that the passage way is clear because there is no restriction to air flow. Even if this worked, the thought of having a permanently clogged pipe and clogged head ports is not appealing to me.

Having BMW clean the heads is NOT a solution to the problem either, just a temporary measure. The heads/pipe get clogged in as little as 9000 miles from new, according to the survey, then those newly "cleaned by BMW" heads will just clog up again. We really need BMW to FIX THIS PROBLEM, not just clean it up to have it come back again!

I don't like the solution that LLCOOLM5 tried - injecting cleaner into the pipe full strength, filling up the pipe with a lot of cleaner. The cleaning fluid will run down into the heads and some of it will invariably end up in the oil. It does not take much to contaminate the oil, causing it to loose it's lubricating properties in a hurry and ruin an engine - and that is not something any of us would want to happen. Older cars with mechanical fuel pumps had that problem when the rubber pump diaphram would crack and let fuel seep into the oil and in no time at all the rings and bearings were worn!

Regarding using the additive, I would DEFINITELY NOT use lead substitute, as "laidbacknags" asks (your name?) I would guess this would damage the cats.

I ifrst used "Lubro-Moly Ventil Sauber" (valve cleaner) and "Lubro-Moly Jectron" (injector cleaner) available from Bavarian Auto
http://www.bavauto.com/shop.asp

Then I switched to Chevron Techron which is readily available at auto parts stores and does not have to be ordered, the larger size treats up to 20 gal. and our tanks are 18 gal. as I recall. Both seem to work. In my experience, Techron has been "the" product to use for so many years, Lubro-moly and Redline products also seem to have great reputations as well.

I don't know if using the Techron will continue to keep the SES light off, my fingers are crossed that it will! I am NOT going to sell my car just because of this carbon issue. These are one of the finest cars ever produced and it is too damn much fun to drive!!!

Tom L.

mjshira · 13th March 2006, 02:29

it would be great to have you post a how to for what you did. My car has 38k and now I am going to run the cleaner with the fuel every third fill up to try and avoid this issue.

tmlesko · 13th March 2006, 15:02

Quote:

Originally Posted by mjshira

it would be great to have you post a how to for what you did. My car has 38k and now I am going to run the cleaner with the fuel every third fill up to try and avoid this issue.

I followed LLcoolM5's instructions on page 5 of this thread, post #145 and then posted my comments on what I did on page 6 of this thread, post #204. If anyone wants me to re-cap what I did, I can do that.

Tom L.

tmlesko · 13th March 2006, 15:08

Here is an interesting site from Chevron relating to gasoline formulation, additives and deposits - worth the read !!!

http://www.chevron.com/products/prod...t/fueladd.shtm

BMW intake valve deposit certification test method (ASTM D 5500) is quoted!

Thoughts Dave?

Tom L.

mjshira · 13th March 2006, 15:08

I think a specific thread would be great, I'll review your posts and those you mentioned. Did you notice a difference in how the car ran?

wilsodh · 13th March 2006, 19:04

Quote:

Originally Posted by tmlesko

Here is an interesting site from Chevron relating to gasoline formulation, additives and deposits - worth the read !!!

http://www.chevron.com/products/prod...t/fueladd.shtm

Hi Tom,

Thanks for the link. It was an interesting read. There are still some questions I'm not clear on. Most notably, the emphasis in the last two decades has been on controlling intake valve and injector deposits (due to Fed/state emissions concerns). Indeed, the fuel additives formulated to address these deposits actually contribute to combustion chamber deposits. Controlling CCD does not seem to have been a priority, presumably because the contribution of CCD to emissions has not been quite as well developed. I'm inclinded to suspect that the major culprit in secondary air system deposits may well be of the CCD type. So one is left wondering whether we face a rather unattractive trade off: if we use the very best gas for fuel injector and intake valve deposits, are we not at greater risk for CCD and secondary air system deposits?

It was also interesting to see in Figure 1 that there is a wide range of susceptibility across car manufacturers to intake valve deposits. Wouldn't it be interesting to see a similar study on secondary air system (SAS) deposits. It would probably be difficult to design such a study (not sure how it would be standardized), but doubtless some SASs are more prone to clogging that others.

Due to the established link between injector/valve deposits and emissions (and the regulatory consequences), some forms of deposits may have been much better funded for study than others. It is ironic that the deposits that are putting the hurt on us actually work to kill an emissions system! Perhaps one of our hopes is the incredible disconnect between Federal emissions repair cost cap guidance and what we are being asked to pay to keep our SASs in working order. Clearly the Fed did not intend for individual consumers to fork over 5 to 8 grand to maintain the cold start emission system on their cars. This is a design deficiency issue that should be addressed by the manufacturer.

A final thought re. the shut off valve. A key function of the shut off valve as I understand it is to prevent the back-flow of exhaust gases into the SAS. I could imagine exhaust back-pressure pushing gases through the system and into the air pump were there no shut off valve. The design of the Peirburg-based SAS looks logical, although ideally perhaps there would be two shut off valves, one for each cylinder back. If the shut off valve is really doing its job, it seems to me exhaust gases would not find these secondary air tubes an attractive place to go because they would be pressure dead-ends. Thats why it is so interesting to see all the carbon building up in these tubes. I suppose we would expect some natural diffusion/displacement to be occuring, but it seems a stretch that passive diffusion would be contributing all this carbon. In addition, some cars clog up much faster than other cars. Is it because some cars have been unlucky at the gas pump? Or is it that some shut off valves are not up to the task of sealing off the SAS against exhaust back pressure, due to manufacturing/QC issues, design deficiency, natural fatigue, or some combination of all three?

In any case, I'm all for anything that helps in the carbon department. The Chevron additives might have some good science behind them. It would be interesting to contact Chevron directly (perhaps with one or two names from the contributing authors on their web page) and inquire about secondary air system deposits, since these were not addressed in their write-up. It would be interesting to hear if they are aware of this problem and if this has been studied at all from an additive standpoint.

Here's to more SES-free miles!

Cheers,
Dave

Jaeger · 13th March 2006, 21:30

Would there be any benefit if BMW replaced the pipe with a pipe that had an internal coating that would be less susceptible to having carbon adhere to it? For example, carbon does not adhere well to copper or glass. Another possiblity is an internal coating of Silcosteel® by Restek.

wilsodh · 13th March 2006, 23:25

Quote:

Originally Posted by Jaeger

Would there be any benefit if BMW replaced the pipe with a pipe that had an internal coating that would be less susceptible to having carbon adhere to it? For example, carbon does not adhere well to copper or glass. Another possiblity is an internal coating of Silcosteel® by Restek.

Jaeger,
Thanks for the post. In theory, it might. While I'm no surface chemist, I did a little digging a while back and didn't have trouble finding a paper that looked at carbon/aluminum. If memory serves, aluminum was shown to provide a good surface for carbon nucleation, which was accelerated in the presence of oxygen. It sounded like a pretty good description of the environment within our secondary aluminum tubes, which might be part of the problem. Anything that inhibits the initial nucleation might be a good thing. I did notice that Restek can't treat aluminum parts though. And the secondary ports in the heads would also have to be dealt with.

Dave

jaj · 14th March 2006, 05:56

The carbon still has to come from somewhere in this complex system. I'm still wondering if it's a weak or failed control valve that's supposed to disconnect the pump, but that doesn't quite close completely after 50,000 miles. That was the thrust of the Porsche 993 experience.

As for chemical treatments, it's a really tough call - 100,000 miles takes a long time to cover, and even a molecular layer at a time will add up eventually (did you know that a tire loses about one molecular layer of tread rubber per revolution, except when there's a sliding or spinning event when it disappears even more rapidly?).

This is a slow and random event - discovering the cause will guide us to a preventative measure. Until then we're just guessing.

Cheers
JJ