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Old 03-03-2015, 10:42 PM
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Carbon Build Up 35d swirl flaps intake manifold M57 with pics

I have a 2008 e70 35d with the M57TU2D30 turbo diesel engine with roughly 80,000 miles. I have read numerous reports of carbon build up (CBU) on the intake manifold/EGR valve/top swirl ports/tangential ports/swirl flaps/intake valves on other diesel BMW engines. In particular, the 335d (which has a slightly different engine from the 35d, but quite similar) has frequently needed walnut blasting of the intake valves and ports. This link from an e90 forum on the M57 turbo diesel engine is one good example of this problem. Many people have used meth injection and/or EGR deletes to combat this. The conventional wisdom is that the 35d does not have much of a problem with carbon build up thanks to a different EGR design, and a heavier load on the engine. Due to a combination of curiosity, and a desire to prevent problems before they occur, I decided to investigate how much CBU I had. My car was running fine (other than a recent bad thermostat resulting in lower than optimal engine temps). There were no check engine lights, or codes that came up on my recently purchased BMWhat OBD scanner.

To cut to the chase, I had good news and bad news.

The bad news: I had quite a bit of CBU on my EGR valve, intake manifold, and tangential swirl flaps.

The good news: The above areas were all relatively easy to clean up. Also, (and I think most importantly) the intake ports and valves were quite clean. I used a Ryobi borescope from Home Depot to get a good look into the intake ports and valves. The top swirl ports had minor to moderate CBU for the first roughly 2 inches or so (the plastic portion of the valve cover). After about 2 inches the plastic valve cover portion converts to metal as the port approaches the intake valve. This metal area had a thin film of oily residue on it, but no CBU at all. I felt confident that the top swirl ports did not warrant aggressive cleaning. The intake valves looked very clean. The tangential ports were nearly pristine (!). Since the intake ports and valves are the hardest to clean (requiring walnut blasting), I choose to think of this as a glass half full situation.

Here is a discussion with pics of what I did. For this post, I will only show what I did after I got the intake manifold off. I'll post another thread with how I got the intake manifold off (this site makes it difficult to upload more than 10 pics at once).

First a bit of terminology. I believe my terms are correct, but I am a hobbyist - not a BMW tech. I am glad to be corrected if I am wrong. [Edit point: Terms edited on 3/4/15 to conform to later information received from ZetaTre in post #4] To the best of my understanding, air in the intake manifold can enter the cylinders via two different intake ports. The top "swirl port" and intake manifold connection is round and is shown with the red arrow below. The "tangential port" and intake manifold connection is rectangular and is shown with the yellow arrow below.




At the intake manifold/tangential port union there is a flap valve that I understand to be termed a "swirl flap." These swirl flaps are controlled by a swirl flap motor, and open/close to varying degrees depending upon a central computer. These will be discussed in greater detail later.

But first, here is a pic of my intake manifold removed: Note the round ends will connect to what are termed the top intake "swirl ports." The rectangular ends connect to what are termed "tangential ports."



Inside the tangential port area of the intake manifold is the swirl flap. Here is a picture of one of my swirl flaps, with quite a bit of CBU.



In order to clean up the swirl flaps, and the intake manifold, it must be disassembled. This is a picture of the underside of the intake manifold:



The swirl motor controls the swirl flaps via an actuator rod. First, remove the 2 torx screws at shown by the yellow arrows above. Then the swirl motor will slide out. Then the swirl actuator rod must be carefully pried out from the clips (red arrows above). Be careful - don't break anything. Neither the motor, nor the actuator rod, nor the swirl flaps can be purchased separately. They can only be purchased as part of the entire roughly $800 intake manifold.

After removing the actuator rod, things should look like this pic:




The red arrow above points to the now released actuator rod. Remove the torx screws shown by the yellow arrows above. Now the swirl flaps are free to be removed. Again - be careful - don't break them! They cannot be purchased separately. So I was very careful to gently remove them with equal pressure on both sides - see pic below:



With some gentle and symmetrical pressure, they all slid out easily. Now into a bin for overnight soaking in a degreaser:




Sorry I don't have pics after cleanup, but I assure you they were pristine!

I removed all the gaskets/rubber washers/retained bolts from the intake manifold and soaked it overnight in a white plastic garbage bin. An industrial degreaser diluted in hot water is what I used. I lined the bin with a garbage bag to make eventual cleanup a bit easier. As you can see, this is not a big deal. It didn't disturb the family dog a bit:



The next morning I used a combination of brushes from Home Depot to scrub out the inside of the intake manifold. Sorry - no pics. But I'd say it was 95% clean.

As I noted above, the tangential ports were essentially pristine. Here is a pic:



I don't have a pic of what the Ryobi borescope revealed of the intake valves (both top swirl port valve and the tangential port valve) - but I didn't think it was worth dealing with a walnut blasting.

The swirl ports were a bit more nuanced. Realize that first 2 inches or so of the swirl ports are plastic, and are part of the valve cover assembly. There I had a moderate amount of CBU. Not nearly as much as shown in the first 335d link that I referenced above, but still some. However, after the top swirl port transitioned to metal, all I had was an oily coating - no CBU at all. This pic hopefully shows what I mean:



This was perhaps the worst of my top swirl ports. As I hope you can appreciate, there is some CBU initially. But as you look down the intake port, one can see the junction between the plastic valve cover where it transitions to metal. Just below that area one can see a clear streak (where the borescope scraped the oily residue off as I threaded it down to inspect the valve). As one can see, clean metal is just below the oily residue. No appreciable CBU. To clean up the CBU on the plastic portion of the valve cover, I first stuffed a bit of lint free rag down the intake port (to stop debris from getting down to the intake valve). Then I scraped the proximal portion of the intake port with a piece of hard wood formed as a scraper. I wanted to be sure not to damage the plastic of the valve cover portion of the intake port. Then I used a shop vac to suck out the debris that accumulated above the lint free rag "plug" mentioned above. Removed the "plug," and all was well.

I replaced the intake manifold gaskets (parts 2 and 3 below).



As an aside, one of my tangential port gaskets was beginning to fail, and there was a very small amount of oil leaking from the # 6 tangential port gasket onto the engine below.

I'll make another post about how to remove the intake manifold. I may not understand the site well enough, but I am not able to upload more than 12 pics at once. So it makes it hard to discuss all aspects of this job in one thread.

I'll be honest and say that my car doesn't seem to be running any differently now - so maybe all my efforts were for naught. But I doubt it - I think that eventually my swirl flaps would have become stuck, with subsequent check engine lights (CELs) and various codes. I keep telling myself that I saved myself from an inopportune future mechanical issue, but who really knows?

Regards.
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Last edited by sgrice; 05-18-2015 at 03:48 PM.
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Old 03-04-2015, 12:54 AM
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Can't see pictures..
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Old 03-04-2015, 08:39 AM
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Sorry the pictures aren't showing. I thought I had it right, but obviously not. I'll work on getting the pics in later today.
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Old 03-04-2015, 09:16 AM
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Can't see pictures, but just wanted to ask how much do you drive it per day?
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Old 03-04-2015, 03:45 PM
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Subscribing as I'm very interested in the picture.

You've probably read it elsewhere, but my theory about CBU is that is the result of very poor control of the amount of oil that gets into the intake through the crankcase ventilation system. This theory comes from the simple observation that if soot alone was the cause, you'd have build up in the EGR cooler, not only the intake. Instead, the residues in the EGR cooler are light and can be easily wiped away while the intake is covered with tar.

Goes without saying that if you remove the soot (by modifying the EGR), you remove 50% of the problem: that's perhaps the reason why the X5 thanks to the LP EGR have less CBU problems.

I actually went the other way and removed the oil from the PCV by installing a ProVent 200 separator that drains the oil back to the sump through the dipstick. Here's my whole endeavor: http://www.xoutpost.com/bmw-sav-foru...separator.html

Not too long ago I cleaned the intake using the Liqui Moly Intake Cleaner. Provided that I have not remove the whole intake yet, when I recently removed the charge pipe it's clear that the EGR valve now has very minor buildup on it and the intake is absolutely dry, there's no oil film on anything and the oil level in the sump remains absolutely the same between oil changes (compared to a shortage of roughly 1qt every 5K miles).

I'll bet you that when you removed your charge pipe you had a little puddle of oil right in front of the flap.

I'm about 3K miles away from next oil change at which point I'm probably gonna update the thread with some pictures. I made it a point to use the Liqui Moly again as a way to slowly clean off what has built up before the ProVent. That stuff is no magic cleaner, but it does melts off the tar from the intake...

PS: you actually got the ports a bit confused. There's a tangential port and a swirl port. The tangential is rectangular and the swirl is round. The flap on the tangential is called "swirl flap" because it closes the tangential and forces the air through the swirl.

Consider the swirl flap open to allow air through the tangential ports under higher engine speed; in general this means that most of the time the swirl flaps are closed. Also higher engine speeds most often come along with higher engine loads in which case makes it more likely for the EGR to be closed. That's likely why your tangential ports are cleaner than the swirl: they are used less and when they are used there's less soot in the air.
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Old 03-04-2015, 05:03 PM
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Hopefully everyone can see the pics now. Sorry for not having them properly up initially.

Pierce330: My car is roughly 5 years and 4 months old, with roughly 80,000 miles. So that averages to about 15,000 miles per year. Daily commute to work is roughly 20 miles each way, of which about 15 is highway.

ZetaTre: Excellent deductions, Sherlock! I did in fact have a small puddle of oil in the throttle body when the charge pipe was removed, as you predicted. Also, just as you say, the EGR cooler itself only has very light residue (like the tangential intake port). I think you are correct with your ideas and effort on the ProVent. And thank you for correcting me about the terms for the different ports - I have edited my original post and hopefully have it correct now. And your thought about why the tangential intake port is so clean is spot on, I suspect.

Regards.
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Old 03-04-2015, 05:07 PM
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Quote:
Originally Posted by sgrice View Post
Hopefully everyone can see the pics now. Sorry for not having them properly up initially.

Pierce330: My car is roughly 5 years and 4 months old, with roughly 80,000 miles. So that averages to about 15,000 miles per year. Daily commute to work is roughly 20 miles each way, of which about 15 is highway.

ZetaTre: Excellent deductions, Sherlock! I did in fact have a small puddle of oil in the throttle body when the charge pipe was removed, as you predicted. Also, just as you say, the EGR cooler itself only has very light residue (like the tangential intake port). I think you are correct with your ideas and effort on the ProVent. And thank you for correcting me about the terms for the different ports - I have edited my original post and hopefully have it correct now. And your thought about why the tangential intake port is so clean is spot on, I suspect.

Regards.
That is fantastic!!!!! Thanks so much for posting this!

I did try to sneak a borescope in the intake on mine, but I couldn't get to the valves.

Btw, how were the overall condition of the swirl flaps? You probably read about problems with earlier M57 models where they would come loose and drop in the intake. The story has it that our version of the M57 has no such problem. Did they feel solid? Any play in the shaft?

Again, great post!!!!!
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Old 03-04-2015, 05:18 PM
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The swirl flaps felt very solid. They opened and closed very smoothly. No play at all in the shaft. Rubber gasket areas all solid. So apparently the design changes were successful!
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Old 03-04-2015, 11:48 PM
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Excellent post by you sgrice!!!Thank you for sharing your work....

I will be doing this while changing glow plugs on mine as i need to remove the intake.
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Old 03-05-2015, 07:54 AM
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Fantastic post. As an owner of a 35d, these posts are very interesting and helpful to me.
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