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      10-06-2012, 03:30 AM   #1
HERR FSTIR
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Carbon Build Up on Intake Valves - Future Maintenance Issue for the 1M

After purchasing my 1M I was considering selling my 2008 335xi. However, I decided to keep it for a winter vehicle. Also, since both cars share virtually the same engine, I figured I could identify and learn how to fix several of the maintenance issues known to affect the N54.

One such issue is carbon build up on the intake valves which is a problem common to many direct injection engines. This issue seems to become manifest around 40-50K miles, although some threads on other forums have indicated significant build up before 30K miles. Oil catch cans and methanol injection may help slow down this process, but do not eliminate the problem.

Since the 1M is a rare car, and many of us plan on owning it indefinitely, I imagine most of us will have to deal with this problem as our baby Ms accumulate more mileage. With this in mind, I thought I would share my experience cleaning the intake valves on my 335.

First, the best way to do this is have a shop clean the valves with aerosolized abrasive material (i.e. walnut shells). The second method, which I used, is to soak the valves in various fuel system solvents and scrub them with a brush. There is a useful DIY on e90post for the soak and scrub method which I basically followed (Intake valve cleaning DIY). Although inferior to the walnut shell method, this still produced a good result. I think I got about 90% of the carbon off.

I spent about 5 hours from start to finish, which included putting in a set of new spark plugs. Disconnect the battery since you will be working close to the starter and it's probably unwise to generate sparks while working with combustible solvents.

Probably the most difficult part is removing the intake manifold since the rear of the manifold near the firewall is sort of held in place by the air charge pipe going to the rear turbo. I would advise completely removing the throttle body from the manifold since it is easy (only 4 bolts) and makes it much easier to detach the manifold from a wiring loom hidden beneath the manifold (see DIY) as well as maneuver the manifold off the head.

Once the manifold is off, the cleaning is tedious but actually not too bad. Having the proper tools is key.

I purchased a number of gun cleaning implements from a local sporting goods store, including multiple brass and nylon rifle barrel cleaning brushes. These brushes are stiff enough to remove the carbon deposits, but don't seem to harm the valves. Make sure to purchase at least 2-3 brushes as they will get heavily caked in carbon and become less and less effective as you move from cylinder to cylinder.

In addition, I purchased a "variety pack" of gun cleaning instruments which included various metal picks similar to what your dentist uses to remove tartar from your teeth. These turned out to be very helpful for some of the hard to reach areas about the valve stem.

You will also need a fair amount of cleaning solvent. I mainly used carburetor cleaner. I used some Techron type cleaning agent as well, but the carburetor cleaner had the advantage of being pressurized in a can, thus helping to turn the carbon debris into a black slurry which could then be sucked out.

Also, make sure you have a good wet/dry vac with an appropriate attachment. I found some very small sized attachments at home depot which connect to the vacuum and fit nicely into the intake port. Alternatively, you could connect some clear 3/8 inch tubing (available at home depot) to your wet/dry vacuum. Having an appropriately size vacuum attachment really made a big difference at sucking out the carbon chunks.

You can work on three cylinders at a time. The valves need to be in closed position to prevent carbon and other debris from going into the combustion chamber. Following the method in the DIY, just fill up the port with some solvent, let it soak, and then scrub. Then use the wet vac with a small nozzle to suck out the dirty fluid. Repeat multiple times until you are satisfied with the result. As shown below, I connected one brush to a cordless drill which I used gently to help get off some of the more recalcitrant chunks of carbon.

To move onto the next group of cylinders you will need to slightly roll the car until the next set of intake valves to be cleaned are in the closed position (assuming you have a manual transmission - a good assumption if you're working on your 1M). This is much easier if the spark plugs are out - so having a new set of spark plugs available is a good idea when you do this.

So was it worth the effort? I'm not sure. The amount of deposited carbon was fairly striking for an engine with 40K miles (see below). Before cleaning the valves, throttle response in my 335 seemed a bit attenuated at low RPMs (perhaps I've simply become accustomed to the lighter flywheel in the 1M!). After cleaning, throttle response with low engine load might be slightly better, but that might be a placebo effect.

One fringe benefit is if you can do this, then you can easily replace your high pressure fuel pump. While scrubbing your valves you will be looking straight at the fuel pump, and replacing it is simply a matter of removing a few allen bolts and disconnecting the fuel lines.

Hopefully, this helps the 1M community down the road.

Images below show degree of carbon build up after 40K miles (running a tune for about 30K miles, no methanol injection or OCC). Brass gun cleaning brush used for scrubbing valves with optional attachment to cordless drill.
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      10-06-2012, 03:40 AM   #2
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Great job. One question when you cleaned closed valves how do you crank/turn engine to close other valves?
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      10-06-2012, 03:49 AM   #3
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Quote:
Originally Posted by RimasRS View Post
Great job. One question when you cleaned closed valves how do you crank/turn engine to close other valves?
You need to roll the car with vehicle in gear (if you have a manual transmission - which of course you do if you are working on a 1M). Rolling the car a couple inches will be enough to position the valves. I strongly advise removing the spark plugs which makes rolling the car much easier (no compression).

If you are working on an automatic you will have to turn the crankshaft with a ratchet or other tool.
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      10-06-2012, 03:55 AM   #4
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Quote:
Originally Posted by HERR FSTIR View Post
You need to roll the car with vehicle in gear (if you have a manual transmission - which of course you do if you are working on a 1M). Rolling the car a couple inches will be enough to position the valves. I strongly advise removing the spark plugs which makes rolling the car much easier (no compression).

If you are working on an automatic you will have to turn the crankshaft with a ratchet or other tool.
Thanks. I have MT that will be another point why I love it

One more question do you think it will be good to use this degreaser it is the best oil cleaner that I have ever used --->
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      10-06-2012, 11:04 AM   #5
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Nice job, thanks for sharing this info. Do you happen to have any after-shots?
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      10-06-2012, 11:14 AM   #6
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Keeper thread and great information. Deserves to be a sticky imo.
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      10-06-2012, 01:32 PM   #7
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Quote:
Originally Posted by ayao View Post
Do you happen to have any after-shots?
Sorry, but I completely forgot to take a picture of the valves after cleaning.

However, my result was similar to that obtained by the guy who put together the DIY thread on e90post, and I will attach his picture.
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Last edited by HERR FSTIR; 10-06-2012 at 02:15 PM.
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      10-06-2012, 02:12 PM   #8
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Quote:
Originally Posted by RimasRS View Post
One more question do you think it will be good to use this degreaser it is the best oil cleaner that I have ever used --->
It's worth trying. To be honest, I think the abrasive action of the brushes is the most important thing, and the solvent is secondary.

Fellow forum member MDORPHIN has previously suggested using a solvent containing PEA (polyetheramine) which can be found in 3M fuel cleaner (See post #87).
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      10-06-2012, 02:14 PM   #9
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Two additional threads which provide a lot of useful pictures and additional information.

http://www.e90post.com/forums/showthread.php?t=520035

http://www.e90post.com/forums/showth...ghlight=carbon
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      10-06-2012, 03:00 PM   #10
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A picture my brother sent me after doing the walnut treatment.
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      10-08-2012, 10:21 AM   #11
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subscribed for later
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      10-09-2012, 03:04 PM   #12
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what is the problem this causes is it valve's sticking or flow past the valve's,looks much better but i fail to see how that helps except for the air flow,i would imagine the problem with the carbon build up valve would be on the valve seat or where the valve goes into the guide
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      10-09-2012, 04:12 PM   #13
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Quote:
Originally Posted by GAZ 345 View Post
i would imagine the problem with the carbon build up valve would be on the valve seat or where the valve goes into the guide
From what I've read carbon build up around the valve seat produces turbulence as the air charge passes into the combustion chamber, thereby altering distribution of fuel injected into the cylinder, which in turn changes the combustion cloud. I don't believe the carbon deposits actually restrain valve movement, and as you reposition the valves during cleaning you can see the upper valve stem is largely free of carbon deposits.
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      10-09-2012, 04:22 PM   #14
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This can occur much earlier than 40k. I had noticeable buildup in my 1er at roughly 18k. After looking into everything else and keeping the car for nearly two weeks (despite my repeated suggestion regarding the buildup), they finally walnut blasted. Drove like a new car.
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      10-09-2012, 05:25 PM   #15
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I installed an OCC on my 1M within the first 5k miles to try and slow down the carbon build-up, we'll see how it works out.

Don't know if this has been brought up before, but is it possible to re-plumb the crankcase ventilation line(s) to be separated from the engine's intake stream?

Atleast the good news is that walnut blasting seems to be extremely effective at cleaning out the carbon
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      10-10-2012, 03:12 AM   #16
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Quote:
Originally Posted by flzrider View Post
Don't know if this has been brought up before, but is it possible to re-plumb the crankcase ventilation line(s) to be separated from the engine's intake stream?
There is discussion of diverting the crankcase ventilation to atmosphere in the following link (see posts #81 & #139): Replacing N54 oil filter housing and cleaning intake valves. Some people point out this produces a fairly noxious odor.

Keep in mind crankcase vapors may be directed either into the rear turbo air intake (if engine is operating on boost) or directly into the intake manifold (engine decelerating with low intake manifold pressure). You can see a schematic and explanation on pages 12-13 from PDF describing N54 mechanical systems.

With respect to using a catch can, I imagine anything is better than stock, but I have come across positive mention of this oil separator (catch can): Mann-Hummel Provent.

Using low volatility engine oils is another approach to limit carbon deposits. The following is a pretty interesting discussion largely based on similar problems occurring with Audi/VW direct injection engines: http://www.bobistheoilguy.com/forums...1325647&page=1.

Here's another thread from an Audi owner having to clean his valves every 7K miles!!
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      10-10-2012, 11:17 AM   #17
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Quote:
Originally Posted by HERR FSTIR View Post
There is discussion of diverting the crankcase ventilation to atmosphere in the following link (see posts #81 & #139): Replacing N54 oil filter housing and cleaning intake valves. Some people point out this produces a fairly noxious odor.

Keep in mind crankcase vapors may be directed either into the rear turbo air intake (if engine is operating on boost) or directly into the intake manifold (engine decelerating with low intake manifold pressure). You can see a schematic and explanation on pages 12-13 from PDF describing N54 mechanical systems.

With respect to using a catch can, I imagine anything is better than stock, but I have come across positive mention of this oil separator (catch can): Mann-Hummel Provent.

Using low volatility engine oils is another approach to limit carbon deposits. The following is a pretty interesting discussion largely based on similar problems occurring with Audi/VW direct injection engines: http://www.bobistheoilguy.com/forums...1325647&page=1.

Here's another thread from an Audi owner having to clean his valves every 7K miles!!

Lots of good info there. Thanks for the links.

I too have heard of the Mann-Hummel oil separator/occ but I have yet to see anyone actually install one on their N54.
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