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BMW DIY Video – Carbon Cleaning N54 and N55 Intake Ports and Valves, De-Carbon, Walnut Blast

July 2, 2014

Come on along as we perform the de-carbon service on a 2007 335i. This vehicle has about 72,000 miles on it and had had this service performed previously, at about 45,000 miles. As you will see, from the video and photos, in just under 30,000 miles, there is significant carbon build-up in the ports and on the intake valves.

It is important to put the vehicle in “sleep mode” before beginning any work.  This powers down all modules and computers, allowing the various sensors to be disconnected without generating faults in the systems.  Perform this step as follows:

1) Place the vehicle in the position where it will be worked on.

2) Open the hood and the driver’s window.  Close all other windows, doors and trunk.

3) Turn off all systems and accessories and remove the key.

4)  Move the key at least 20 feet away from the vehicle.

5) Apply parking brake and place transmission in NEUTRAL (manual transmission) or PARK (automatic transmission)

6) Wait 20 minutes.

7) Once the vehicle is in the sleep mode, do not activate any electrical accessories or systems (besides bumping the starter, as shown), close the hood or open the doors, trunk or windows.

How to assemble and set-up your BAVauto® Media Blaster:

As we move further into the 21st century, many auto manufacturers are turning to engine management systems that employ “direct injection” fuel injection systems. Direct injection systems inject the fuel directly into the combustion chamber at the precise timing for optimum power and/or economy under a specific operating condition, or parameter. Diesel engines have used direct injection for many years, in order to optimize power output, fuel economy and engine oil life. Direct injection involves mounting the fuel injector so that it sprays (or injects) the fuel into the cylinder combustion chamber at the optimum point in piston travel and cylinder compression. This allows very precise control of the fuel delivery. Standard (non-direct) injection systems mount the injector in the intake port or the intake manifold (or even way back at the throttle body). While these systems typically offer more precise fuel delivery than a common carburetor, they do still have efficiency losses, compared to direct injection.

With all of this “good” going on for direct injection’s use on gasoline 4-stroke engines, there are some potential drawbacks. Since the fuel is being injected directly into the cylinder’s combustion chamber, the intake runners, cylinder head intake ports and the intake valves are only bathed with air. In other words, unlike engines with standard fuel injection systems, the ports and intake valves are dry. At least, that’s the idea.
Depending on the design and efficiency of the crankcase ventilation system (or, Positive Crankcase Ventilation, PCV), some amount of oil vapor will be introduced into the intake manifold, cylinder head intake ports and the intake valves. When this oil vapor hits the hot cylinder head intake ports and the intake valves, it burns and sticks to the surfaces. Over time, this results in moderate to heavy build-up of carbon deposits. These deposits disrupt and even reduce the intake air flow, into the cylinders, ultimately robbing power and economy. While most engine designs must deal with this oil vapor from the PCV system, a non-direct injected engine is spraying fuel into the intake ports and over the intake valves, effectively cooling, lubricating and washing the surfaces, which prevents the heavy carbon build-up that we can see in the direct injected engines.

With the introduction (in the US) of the N54 twin turbo 6-cylinder engines in the late 2000s (135i, 335i, 535i, X5), and now the N55 single turbo, N20 4-cylinder turbo and all the rest of the turbo and naturally aspirated “N” 4-clyinder, 6–cylinder and V8 engine family, we are seeing the effects of heavy carbon build-up in the intake ports and valves. BMW has even recognized this and has implemented a “de-carbon” program for many of these engines. The N54 and N55 twin and single turbo engines are the most susceptible to the heavy carboning (so far). BMW dealers will be happy to perform the de-carbon service for a fee of $600 to $800, and up. The de-carbon service involves removal of the intake manifold and blasting of the ports and valves with walnut shells, using a special fixture (plus a media blaster and a shop-vac).

The de-carbon service is really not all that difficult, but does require some special tools, as noted above. Bavarian Autosport has developed a full Do It Yourself (DIY) program for the de-carbon service on the N54 twin turbo engines (more to come, just ask us if you have a different model). We will provide the special adapters, media blaster, walnut shell media, replacement gaskets and full video instruction. The media blaster kit is available for purchase or rental. Call our advisors at 800-535-2002 or visit our online store at for details.

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• New & Rental Media Blaster Kits (click image):

Walnut shell blasting media:

• Torx bit set, 3/8” drive:

• Fender protector mat:

• Shop vacuum with hose adapter
• Eye protection
• Hearing protection
• 3/8” drive metric socket and ratchet set, 8mm through 13mm
• Various screwdrivers


• Throttle-body gasket (click image):

* Intake manifold gasket set:

Bavarian Autosport

  1. Ed Walker permalink

    Doesn’t look too tough. One thing, I don’t like the idea of sparking over the starter motor like that. With the complexity of electronics in modern BMWs I would hate to fry my computer. Wouldn’t it be safer to put a wrench on the crank, and slowly move it around to make sure the port you are working on is closed? Or is it impossible to get a socket on the crank?

    Thanks for the vid.

    • You can certainly turn the engine manually. It is near impossible to get a tool on the crank bolt in any convenient fashion. You could also have the transmission in-gear (if it is a manual trans) and rock the car. Note in our full description of the task, that you must “put the car to sleep”. This assures no problems with the electrical system or computers when disconnecting sensors or while bumping the starter.

  2. Marshall Garrison permalink

    If the car has a manual transmission, does releasing the parking brake & putting it into gear “wake” up the car? Although it might take supporting the car by jack stands on the rear trailing arms (so the rear suspension is not at risk of any components being damaged due to being at full droop), with the rear wheels off the ground & the car in gear, turning the rear wheels manually by some means, perhaps a breaker bar on the lug bolts, could move the engine through the positions needed for the walnut blasting.

    Obviously, adding such extra steps means extra precautions for jacking safety, working on a level surface, and so on. I presume on any awd “X” models, all 4 wheels would have to be off the ground.

    • Rotating one rear wheel may not work well, as these cars generally do not have “posi” differentials. However, if you were to try (rotate both rear wheels?), set the car up for this before putting it to sleep.

  3. Steve2002 permalink


    Have you seen this carbon build up issue on 328I N51 non-turbo engines?

    • We are thinking that all of the direct injection engines (turbo or not) will end up having issues with carbon build up … to one degree or another. We have not yet pulled apart a non-turbo direct injection engine to inspect it, but we will at some point.

      Note that the N51 328i in NOT a direct injection engine.

  4. Richard Wyman permalink

    Do you think you might develop an adapter to enable use of this kit with Diesel engines? (I have a 2009 335d)– as of Fall 2013, Tully BMW (NH) was apparently one of few (only?) dealers who could do walnut blasting for diesels- otherwise diesel owners were faced with $8000 engine “rebuilds” of sorts….

    • We are working on acquiring the BMW tools for the diesels. Note that the diesel procedure is quite a bit more work …. but still doable by a competent DIYer. Please email [email protected] and note that Otto asked you to do so, for more info on this.

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