Much has been written on the subject of carbon buildup (CB)in the MINI engine, so this may not be anything new. Recently I talked to a guy in the service department at a MINI dealership and I heard some interesting statements.

Specifically he stated that they had only seen CB in the S models (as they use direct injection) and only in those with auto transmissions. His conclusion was that those cars are more often operated a lower rpm's. The cars with stick shift are less inclined to suffer CB because they tend to be driven at higher rpm's. This seemed to make sense, but I haven't any first hand experience and I do tend to be a skeptic. In addition, I have no idea how many cars they have seen over what period of time.

Therefore, I am curious to see whether any of our members can confirm or refute this. Forgive me for not having the patience to search each thread on CB to see what transmission was involved. I understand that anything derived from this may be anecdotal unless someone has access to a detailed study.

 

I just had a check up and asked to have Narcissa looked at for Carbon Build up, and the guy at Keeler Mini in Latham NY said the same thing. He only say it on automatics and not sticks...

 

Not necessarily limited to automatics. I had CB issues addressed and I have an '07 MCS MT which sees spirited driving every day.

 

R53 here, my intake manifold is currently off while handling a carbon build up issue causing misfires in Cyl 3 and 4. Looks much different than those on the R56s (not the whole intake port, just very dirty on the backside of the valves) but it happens.

If you're looking for R56 only data then let me know and I'll move the thread to 2nd Gen.

 

I just had had my 2009 Automatic Mini Cooper S in the shop for 3 days after I got the yellow indicator light and brought it in. Sure enough...carbon buildup and bent valves. They cleaned it out and couldn't give me a good reason for why this happens and whether it will happen again. Luckily this job was covered under my warranty but I don't want it to happen again. Trying to see what others are posting in this forum on this for preventative maintenance....

 

I don't know if there's really a difference whether the MINI is manual or automatic (mine is automatic), but several of us just did Seafoam treatments (u can get it at any AutoZone or Pep Boys shop), which helps w/CB. I did it 4 the 1st time, but didn't get the desired visual proof (lots of white smoke at high rpms), but 1 of our guys (manual) did ... it was awesome! So, u might wanna try that.

 

Did they give you a reason for the bent valves ? I would be very concerned about how the valves became bent in the first place!

It takes great exerted force to bend a valve, and the only way is piston contact, and now you should be asking, why have you suffered from valve/piston contact ? And the most common factor for this is, from timing misalignment, this can be caused from the incorrect applied fastening torque, to either the crankshaft or camshaft sprocket retaining bolts.

Some early engines had the wrong applied fastening torque to the crankshaft sprocket/pulley retaining bolt, this allowed the timing to slip enough to have valve to piston contact, and in most cases it was a very light kiss indeed, but still a kiss nevertheless, also if you've had your timing chain and tensioner replaced, there also could have been some initial timing misalignment by the technician, which may have done the job.

You should now be asking what damage there was/is to the piston crown ? as you may have problems later when your out of warranty! And what are they BMW MINI going to do about it, if you suffer from a failed piston/s out of warranty, knowing that you've had bent valves replaced.

I think we need to get things straight here, about the effects of any, detergent chemical additive for carbon deposit removal, administered through the PCV line whilst your engine is idling, firstly, have a little think about your engines idle speed, 800rpm usually, that's 800 crankshaft revolutions every minute, this in turn is rotating the camshafts 400 revolutions every minute, that in turn is 6.6 camshaft revolutions every second, and that equates to your inlet and exhaust valves opening and closing 6.6 times every second at an engines constant idle speed of 800rpm.

So now ask yourself, how long your "additive" actually spends in contact with and cleaning carbon deposit from your inlet valves ? If your answer is anything other than milliseconds, your sadly disillusioned.

All the White/Blueish smoke you get from the exhaust, when you've administered Seafoam or any other detergent, into the combustion cylinder, is only the sticky residue of the oil mist that has contaminated the top of the piston crown, the roof of the cylinder head chamber, the tip of the fuel injector, and the valve faces, being removed and burnt, along with the chemical detergent itself, as for actual burnt on carbon deposit on the backs of the inlet valves, re-read about the actual physical time your chemical detergent, actually spends attacking the hard burnt on carbon deposit on the backs of the inlet valves!

 

I just had my intake off this weekend to clean the carbon off. Happy to say there wasn't that much on there. I contribute some of that to the Seafoam treatments I have done. I also have a OCC and a Meth kit but the Meth kit was just added. With repeated cleaning and blowing out I did get carbon bits out along with brown stained carburetor cleaner. I repeated this until it was clean that I blew it out on.

I am not delusional to thin an oily substance will coat something and not get sucked off immediately. The carb cleaner worked cold. I think Seafoam would work better as it gets to work while hot. I am not convened it works but you haven't convened me that it doesn't.

Scientific testing would prove if it worked.

 

Czar - Thanks for the perspective here...I'm not a mechanic by any means but the bent valves did concern me...and the service advisor said that the carbon build up would have caused it....sounds like that isn't possible from your view. Is the next question whether there there is a torque issue somewhere?

I have not had a timing chain or other major work done prior to this other than replacing front brakes. My mini has just over 31K miles on it so I'm really unsure of what my next step is here...they cleaned out the carbon and replaced the bent valves and test drove it for about 20 miles before I came home with it...

 

The only possible way for carbon build up to aid in the valve/s becoming bent is, heavy deposits of oil mist residue builds up on the inlet valve/stem, this sticky residue, can in a few rare cases, be of sufficient contamination build up, it can and has been known to hold the valve open, albeit for a very very brief moment, but that's all it takes for the valve/s to be open at the wrong time, during the compression or exhaust stroke, and hey presto you will get valve to piston contact, resulting in a bent valve/s.

excessive oil mist residue (carbon build up) at such low mileage, is generally brought on by either, short journeys, which do not allow the engine to get to full working temperature, engines which constantly see very low RPM's each and every time they are run, excessive crankcase pressure from poor combustion sealing of the piston rings, which picks up more oil than normal, all the afore mentioned, lead to significant amounts of sticky oil mist residue build up.

Now in your case, you should ask your repairing dealer for a report on the condition of your pistons, and get BMW MINI to give you a written document covering you from future blame, should you have a piston/s failure whilst in or out of warranty, given a reasonable amount of time outside of warranty, your piston crowns will at the very least look something like this, this damage was enough to bend the valves, and hold them open, which resulted in total non running, from total loss of compression.

 

Your OCC will be to thank for the lack of heavy sustained carbon build up, your Seafoam treatments, will have played little to nothing on the actual reduction of the formation of the carbon deposit, or lack of in your case, on the inlet valve/stem, and your water/meth kit will be another good aid in the fight against carbon deposit, however that said, your water/meth kit will only play a real significant role against the fight of carbon deposit, depending on your nozzle/s location and the % mix.

Now I'm not here to try convince you or anyone else, as to the effects of seafoam or any other chemical additive, when administered through the PCV line, with the engine idling, what I have described is actual fact, and it's up to you or anyone else if you take notice of my factual advice.

 

You do state a lot of facts. Scientific proof you have not shown. I don't think it is a a medical cure, but I also don't think it dose nothing. If it cleans buildup before it bakes into carbon that would be a good thing.

 

Your quite right, I do state a lot of facts, I think I more than adequately qualify to give factual advice, as I have been working in the Motorsport industry, long enough, 28 years in fact, to know whats what, without having to provide scientific proof, you really don't need to have scientific proof, to understand what this thread is about, or the effects of carbon build up from a DI (direct injection) engine over carbon deposit found and seen in a regular port fuel injected intake system, where Seafoam and other chemical additives, will have more of a positive effect at carbon deposit removal, than what will ever take place in a DI intake system.

 

 

You wanted a "count" of mini's with carbon build up. I have an S with 58,000 miles that was just diagnosed with carbon build up after they changed out the spark plugs and coils to no avail. This mini is a stick shift and of course, not under warranty. Any ideas of a inexpensive way to correct this problem?