Secondary Air System Carbon Build Up Removal Pictures - Page 4 - BMW M5 Forum and M6 Forums
E39 M5 and E52 Z8 Discussion 1998-2003 Advertiser's Forum

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post #31 of 327 Old 11th November 2008, 08:31 PM
TMcNasty
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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...

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!
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post #32 of 327 Old 11th November 2008, 09:04 PM Thread Starter
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Quote:
Originally Posted by SoCaLE39 View Post
What is the mileage on this motor?

Just under 100,000 miles
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post #33 of 327 Old 11th November 2008, 09:21 PM
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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!
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post #34 of 327 Old 11th November 2008, 09:27 PM Thread Starter
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Quote:
Originally Posted by kosmo View Post
Mert, what was the total man hours???
job is not complete, still waiting for heads from machine shop.

I believe the job pays just over 40 hours with additional cost from machine shop cleaning and further inspection.
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post #35 of 327 Old 11th November 2008, 09:42 PM
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Originally Posted by bluemajik View Post
If this would have come out when the e39 M5s first were marketed they would have not sold a single one.
I would have still bought mine.

Steve
00 M5, since new.
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post #36 of 327 Old 11th November 2008, 09:49 PM
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Thumbs down 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. 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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IMG_00861.1JPG (valves).jpg   IMG_00971.JPG (piston top1).jpg  
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post #37 of 327 Old 11th November 2008, 09:58 PM Thread Starter
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Quote:
Originally Posted by TMcNasty View Post
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...

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!

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.
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post #38 of 327 Old 11th November 2008, 09:58 PM
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Quote:
Originally Posted by mertm5 View Post
Hello everyone. My name is Mert. I






removal of carbon with reaming tool and then bristle tool



Hope this helps out.

Mert

Well, perhaps I have not been paying attention, but this picture was a surprise to me!

Anyone suspect that welding these opening closed would be a permanent 'fix' to this problem?


Thanks Mert- will add to FAQ

A
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post #39 of 327 Old 11th November 2008, 10:15 PM
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post #40 of 327 Old 11th November 2008, 10:16 PM
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here's a little comparison of a few motors that have been opened up. Not sure what year mertm5 is working on...
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2002 M5 Lemans Blue
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