Cleaning of intake valves with walnut shell blasting tool - review
By: Mike Ngo and Eurowise
Modern engines are often direct injection, as this process allows for advantages in fuel consumption as compared to conventional fuel injection, as well as yielding more power with an engine of identical displacement. The N54 engine of the BMW 335i and 135i also are direct injection; this means in particular that the fuel is injected directly into the combustion chamber of each cylinder and not in the intake tract. As a consequence thereof, the fuel injectors are no more placed before the intake valve, but directly in the cylinder itself.
The disadvantage of this is that the regular bathing and therefor cleaning of the intake valves by way of the fuel that they are exposed to does not happen anymore. The intake valves are only in contact with air or rather blow by gases from the crankcase breathing circuit, in which substantial quantities of fuel and oil can be found. Over time, these lead to deposits of carbonized fuel and oil in the intake tract as well as on the intake valves themselves; this is also referred to as carbonizing. This is not immediately bad for the engine, but over time can have a detrimental effect on its efficiency. If the valves are heavily carbonized, they may not close properly anymore, and symptoms such as a bumpy idle, vibrations and diminished throttle response can be observed; it may also contribute to increased oil consumption.
As unfortunately this carbonizing effect is an inevitable byproduct of direct injection, it cannot be prevented. The use of additives in the fuel itself is useless, as (see above) the fuel does not come into contact with the intake tract or the valves at all; the use of water/methanol injection may slow down the carbonizing somewhat (depending on where the methanol is injected and provided it is not yet completely vaporized when it reaches the valves), but cannot prevent it either. A cleaning of the intake valves by using Sea foam or similar products which are injected directly into the charge pipe has been discussed extensively, but in my opinion this method is not very efficient as the carbonizing is usually too persistent to be removed by this method.
In principle there are a few methods to clean the intake valves and intake tracts of the BMW N54 engine (and any other direct injection engine). A very elaborate and consequently expensive method is to completely take off the cylinder head and to have the valves lie in a very aggressive cleaning solution for at least 48 hours, after which they have to be cleaned manually as well in order to remove any remaining carbonizing.
The method I chose in the end and that I'm going to describe here is the cleaning of the intake tract and valve of each cylinder with the Eastwood Small Job Media Blasting Kit. We chose to have them mix up a small batch of walnut shell granules to blast the intake tract with. These granules hit the carbon at high speed and remove it entirely, while at the same time this material is soft enough not to damage the metal of the intake tract and the valves.
Here are the basic steps to cleaning your intake ports and valves:
1. Remove intake manifold
2. Put engine valves on the cylinders being worked on at TDC so the valves are closed
3. Tape off all the cylinders not being cleaned.
4. Using a pick, break loose all the cylinders that have large chunks of carbon first and blow them out
5. Prepare the Eastwood Small Job Blasting Kit and cover the engine bay of all walnuts that may go into items you don’t want them to go acess
6. Start blasting
7. After each cylinder blow or vacuum out the material left inside and repeat if necessary