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So I was thinking about the carbon cleaning issue recently and have read up plenty online about the issue and came across a guy in the states that used crushed walnut shells to clean up his valves with very good results.

He discovered that BMW had developed a specific tool for cleaning the carbon from valves using crushed walnut shells and managed to get hold of one but unfortunately i cant find anything relating to it in the UK.

So i was thinking about borrowing a compressor from a friend and buying the following as a simpler/quicker way of the traditional soak and scrape method.

Abrasive blast gun - http://www.ebay.co.uk/itm/New-Abrasive- ... 2326326ef4

Crushed walnut shells - http://www.ebay.co.uk/itm/WALNUT-SHELL- ... 1c2e893345

The only thing that might need some experimentation would be the air pressure for blasting?

Heres an example of it being done on a mini with the BMW tool - http://www.youtube.com/watch?v=R-HlWELr4Zk

Some before and after pics here - http://www.vacmotorsports.com/blog/vac- ... -cleaning/

Here's the original thread I was reading - http://www.e90post.com/forums/showthread.php?t=682116

Whoa - interesting if horrendously messy.

Personally, I would interested in seeing how the dry ice / co2 cleaning process works. The advantage of this is that being pure frozen co2 it won't do any damage as it'll evaporate within minutes (I'd guess) and considerably less mess .
Some impressive videos on YouTube but no idea how it stacks up against valve deposits.

We use coconut husk at work for dry blasting paint off of components. Normally operating around 30psi, any higher and the husk breaks down into unusable dust. You will still need some sort of clean after to remove dust from the husk/walnut. Got me thinking... Any aerospace grade chlorinated hydrocarbon degreasing solvent probably could be used to break down the carbon??

i read not to use any blasting as it can damage the valves, i used brake cleaner flat head screw driver and a toothbrush, and hard scrubbing, it makes a bloody mess though

If you use the right stuff blasting is fine

What about Terraclean?

Terraclean has been suggested but they provide no proof of its effectiveness on direct injection cars.

The issue being that the carbon build up is caused by direct injection and thus no fuel washing over the inlet valves; this means that the formulation used in the terraclean process will also be injected directly and never actually come into contact with the problem area.

I've wondered if Potassium Hydroxide (Oven cleaner) would do the job.... or would it be too caustic on the metals ?

After all, it removed plenty of burnt-on carbon in ovens !

Timster wrote:I've wondered if Potassium Hydroxide (Oven cleaner) would do the job.... or would it be too caustic on the metals ?

After all, it removed plenty of burnt-on carbon in ovens !

Don't be so stupid. The engine is aluminium and you want to dump Potassium Hydroxide on it?

Sodium hydroxide (caustic soda) normally is the active ingredient in oven type cleaners. As ads has said, not suitable for engine parts. Get an ally oven tray and put this stuff on it, it's rather effective at etching it! Perfect as a pre-Cleaner prior to anodising

Yeah been mentioned before.. Not sure if its been tried by in theory much better an less mess than walnut shells

adsgreen wrote:Yeah been mentioned before.. Not sure if its been tried by in theory much better an less mess than walnut shells

Would be interesting to see if you could fire it straight though the air intake with no need to dissemble the inlet manifold, you can buy the dry ice machine new for about 2K guess there wont be many tuners offering this as a service when they can charge £500-800 it

AKA-K3 wrote:

adsgreen wrote:Yeah been mentioned before.. Not sure if its been tried by in theory much better an less mess than walnut shells

Would be interesting to see if you could fire it straight though the air intake with no need to dissemble the inlet manifold, you can buy the dry ice machine new for about 2K guess there wont be many tuners offering this as a service when they can charge £500-800 it

No chance it'd work. The manifold is actually made up of 8 tubes leading to the cylinders. Given the characteristics of the engine the length of these is pretty much dictated by the science and this is actually longer than would fit under the bonnet. As such in the RS4/5 they are bent over by about 150 degrees. So the actual intake trumpets are effectively suspended upsidedown inside the manifold centre airbox. Squirting anything like dry ice into the primary throttle body would be gone by the time any found it's way in. And without the engine running i doubt if any would.

If you look at all the videos you need to be reasonably close to what you are cleaning so no, manidolf off job. However... removing a manifold for an experienced bod shouldn't be more than 45 minutes/1 hour. the hard 2-3 day job is the actual cleaning... if this did work then you could probably do the whole job comfortably in a day.