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Secondary Air System Carbon Build Up Removal Pictures

281K views 329 replies 110 participants last post by  Sailor24 
#1 ·
Hello everyone. My name is Mert. I'm a fellow board member (recently posted pictures of my car), enthusiast, and also a BMW Master technician. Thought I would share some pictures I took at the dealer concerning the SECONDARY AIR SYSTEM CARBON BUILD UP. This is not a DIY thread, but more of an understanding of the procedure. I cannot give out any information about this vehicle but to let you know this is a E39 M5.

carbon build up does not affect just the secondary air system but also the combustion chamber









exhaust valvetrain





secondary air entry port





rear of the cylinder head with the secondary air port freeze plug drilled out and ready for removal. there are three freeze plugs for the secondary air passages that need to be removed and ports cleaned out



rear freeze plug (#1) removed. pictures show cylinder head upside down on cylinder head stand to perform procedure



special cleaning tool (looks like a rifle barrel cleanng rod). Tool is used with a drill and passed through the secondary air main port.





halfway through the secondary air main port, we hit solid carbon. Let me be the one to tell you, it's like hitting solid metal. Took some time to get though it but we did



after cleaning out main port




this is the front of the cylinder head showing the entry of the main port and also the front main port freeze plug (#2). When looking at the front of the cylinder head, the secondary air pump pumps air into the main port entry of the head then immediately makes a 90 degree turn through a short passage way in the front of the head then makes another 90 degree turn and through to the back of the cylinder head into smaller individual ports to each exhaust valve port



this is the freeze plug (#3) that goes from the entry port through the short passage port to the main port



side view of head showing route of air passage



the smaller individual secondary air ports to each exahaust valve port. the right port in the picture looks to be unclogged, but is clogged about halfway through



removal of carbon with reaming tool and then bristle tool





left port after procedure. you can see the difference in diameter



both ports after procedure



all exhaust valve air ports cleaned out



both cylinder heads are being sent out for further cleaning and inspection. this would be the perfect time to get any cylinder head performance work done.

Hope this helps out.

Mert
 
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#4 ·
Wow, what pictures!
What a job!
In a nutshell, what causes this problem? bad fuel? Excessive idling? What?

Neil
 
#6 ·
Fantastic post! Thanks for the clear pictures of the secondary air issue as it is much easier to understand now. Given that the ONLY purpose for the secondary air system is cold start emissions, I'm guessing Powerchip is going to be reeling in some income as E39 M5s age. :)

Thanks again for such great pictures and description.

Chuck
 
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#12 ·
So from now on, when some one says they fixed their carbon build up with a power-chip, all they did was get the code permanently erased. I hate when people who are selling m5's say " Carbon build-up fixed with power-chip"
 
#13 ·
The inside of that engine looks horrible. To think mine looks similar just makes me cringe. Not what I needed to see since I'm getting ready to put a new suspension in, new wheel bearings and new p/s lines.
 
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#14 ·
What is the mileage on this motor?
 
#17 ·
It's a con only if Powerchip didn't tell you what they were doing. They do, so no it's not a con. It doesn't "fix" the carbon buildup, it only keeps the CEL from lighting so the car will pass inspection. From what I've read the cleaning procedure will cost big bucks. And then it could happen again.

Powerchip is a solution, not an actual fix.
 
#19 ·
I dont understand how you guys can call Powerchip a con. Its a very sensible solution given that the only other option is spending $8k for BMW to clean it out or at least half that with any indy shop. Let's not forget, as stated earlier, this problem could come back.

Looking at this engine, there seems to be more carbon buildup on the pistons than normal compared to other s62 engines I have seen.
 
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#20 ·
great pictures and post Mert. I'm also curious how many miles were on this car. I can post some pics tonight of my car at 72k miles when the heads came off, it was much cleaner, wrt carbon. (heads were coming off for other reasons.)
 
#21 ·
Would a regular chamber cleaning additive help with this problem?
 
#23 ·
Awesome pictures and info, Mert.

But, I doubt the cylinder carbon build up is "caused by the secondary air system." It appears that the owner was just not running the car hard enough ... AT ALL. I have seen other non-BMW engines that were similarly "abused," to my way of thinking, without any secondary air system involved, and they were every bit as bad. Some were worse, if you can believe it. Carbon is one MEAN molecule ... well, except when it morfs into diamonds.

Thanks again. The pictures tell a much better story than just text, at least for me. (I'm "A picture is worth a thousand words" kinda guy.)
 
#24 ·
But, I doubt the cylinder carbon build up is "caused by the secondary air system." It appears that the owner was just not running the car hard enough ... AT ALL. I have seen other non-BMW engines that were similarly "abused," to my way of thinking, without any secondary air system involved, and they were every bit as bad. Some were worse, if you can believe it. Carbon is one MEAN molecule ... well, except when it morfs into diamonds.
Exactly. Perhaps that's not obvious to others though that are seeing this thread. All the more reason to only use top tier gas and also use Techron on a regular basis in additon to NOT driving an S62 like a donkey cart. :) This engine is made to run and run hard.
 
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#26 ·
regarding the powerchip fix. Keep in mind that powerchip borrowed a line or two of code out of a euro dme, more or less (i'm probably oversimplifying).

I had noticed a few years ago, when we started seeing the carbon build up SES lights in US spec cars, that none of our european members had it. The engines are the same, and i didn't buy that it was just a fuel issue. I emailed powerchip and mentioned this to them, and asked if they could look into a euro dme to see if secondary air flow was actually monitored (with regard to the SES light). It wasn't so, so the "fix" was relatively simple, take some code from a euro dme (which does not check for sec. air flow) and apply it to the US dme.
 
#92 ·
regarding the powerchip fix. Keep in mind that powerchip borrowed a line or two of code out of a euro dme, more or less (i'm probably oversimplifying).

I had noticed a few years ago, when we started seeing the carbon build up SES lights in US spec cars, that none of our european members had it. The engines are the same, and i didn't buy that it was just a fuel issue. I emailed powerchip and mentioned this to them, and asked if they could look into a euro dme to see if secondary air flow was actually monitored (with regard to the SES light). It wasn't so, so the "fix" was relatively simple, take some code from a euro dme (which does not check for sec. air flow) and apply it to the US dme.
Not sure if that is entirely true, I have seen 2 E39 M5's with the AA code, both Euro cars, both in the UK.

Richie.
 
#28 ·
Me either. After just purchasing my beast I am very sad that this can happen. I hope BMW has addressed this problem with the e60 or any other engines they build. I think this is why we have recalls. Wow. If this would have come out when the e39 M5s first were marketed they would have not sold a single one.
 
#29 ·
recalls are typically for safety related defects. This would probably come under 'normal wear and tear.' I don't think the german engineers really think about lifespan beyond 100k miles. Euro emission laws must not either.
 
#31 ·
Mert is this you working on your own car or is this a customer car?

Anyway...seeing all that carbon in the cylinders doesn't surprise me. I theorized in another thread that the CBU starts in the cylinders. I know thats totally obvious so...ouich

But seriously, a well running combustion chamber (IMHO) releases way less "stuff" that can get into these ports and (again IMHO) finish combusting in these channels in the hot environment. Older M5's with the more oil passing by the rings are even more susceptible.

Even if the exhaust isn't completing combustion in these channels...the exhaust system is a positive pressure environment. The gasses are being forced down the exhaust system under some pressure. This pressurized gas is always looking for a way out. Perhaps the addition of a one-way check valve in the SAP air line right where it enters the head would help. I'd bet that once the SAP turns off it's not airtight internally and this enables the exhaust air to travel thru the channels and exit out the SAP thru the SAP pumps fresh air intake. A one-way check valve at the entrance to the head would stop this if indeed it's happening as I suspect. Maybe mert could tell us if that SAP itself is loaded internally with CBU?

One other thing that I think would slow it down or stop it from happening is to have the secondary air pump running all the time the car is on. Not full power of course...maybe just at a few % of it's normal running speed, but not so much that the pre-cat O2's see excessive oxygen in the exhaust. This would create a positive pressure inside the small channels and keep the exhaust gasses at bay.

I'm not letting BMW off the hook for any design flaws here. I'm sure in hindsight they see where they went wrong. However I think this manually cleaning is treating the symptom not the cause. They should look for a solution for the SAPs shortcomings. My suggestions may not be the be all end all, but there's a decent CHANCE they could help. I think $8,000 with the threat of reoccurance shouldn't be their only response.

As far as us owners go in the short term the only thing I can suggest is RELIGIOUS maintenance and a shortening of any published BMW schedules for things like air filters, spark plugs, pre-cat O2 sensors etc. And monitoring the health of your thermostat. ANYTHING that affects combustion efficiency!
 
#37 ·
the secondary air pump itself does not have carbon build up. there is a secondary air non-return valve (which is functioning properly, air tight) between air pump and cylinder heads that is attached to the aluminum transfer pipe. the aluminum transfer pipe did also have carbon build up which was removed first to determine that the cylinder heads may be clogged.
 
#33 ·
I would love to know some history on the car....service intervals, oil consumption, fuel used, usage (city, highway), etc. I have rebuilt a number of older BMW motors with a lot more miles than 100K and have never seen them look this bad. I wonder how this car ran? Thanks for the post mertm5!
 
#36 ·
Great pix! And a word of caution...

Mert - thanks for taking the time to post some great photos that help clarify the secondary air system. :thumbsup: I wish these photos were available a few years ago when we first began writing extensively about this problem.

I would caution everyone that those nasty looking combustion chambers are not necessarily cause/effect for clogged secondary air system passages. The photos below were taken from a member who's engine had ~100k miles and was diagnosed with a carbon-clogged SAS. However, the combustion chambers don't look bad at all. Note the clean valve edges. The BMW mechanic remarked at the time that, apart from the clogged SAS passages, the tear-down presented an otherwise normal, well maintained engine.

The evidence points to a separate chronic process by which the SAS passages become occluded. During our carbon build up survey a couple of years ago, we could not find a correlation between carbon build up and driving style, gas used, or oil consumption (n = 20 something respondents reporting the issue). Even engine mileage presented some unexpected outliers (some low mileage cars had the problem).

I'd agree that its probably not a bad idea to run up your cylinder head temps on occasion with spirited driving to reduce soft carbon in the combustion chamber, but there is no evidence I'm aware of that this is helpful for SAS carbon build up.

Dave
 

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