So we picked up that 2011 Cooper (N16) for my son last week end.. No CEL but some codes here and there - largely reset with a new battery... A few misfire codes (old? new? who knows) but not enough to trigger a dash light apparently. Also some ticking (not too loud, not just startup) that made me think "belt or chain tensioner" initially - despite the N16 reputation as being less troublesome with chain tensioners.

Today we did basic maintenance (teaching the kid to take car of his ride) and got a few surprises
- The mini plugs are non standard (to me), I had to go buy a new spark plug socket that fit those ;-)
- One of the spark plug tubes (left most Cyl facing the engine) was literally filled with 1" of oil !! Not quite enough to get in the coil or reach the top of the electrode but sheesh ! 2 more plugs were 117000 miles old and hairy. And the 4th had pieces of a broken metal ring around it, which I saw by total dumb luck. Actually those were magnetic... Looks like a piece of a previous plug socket fell in and was never noticed. I extracted it with a magnet before removing the plug so nothing fell in the engine ! Phew
- the car was short 1 qt (possibly 1.5!) - not exact here as I spilled some from the filter etc...
After fixing all that, the ticking immediately went completely away, the misfires never reappeared (yet) on the error codes, and the car purrs like a swiss watch. For good measure I also changed oil, filter, coils, air filter and cabin filter with my son and am sending an oil sample to blacktone labs to see what's in there.

Q: Guessing the plugs were original - well maybe not #4 with the magnetic ring broken on it - looks like someone tried to change that one. The engine runs perfect so I doubt a more serious issue. I imagine the issue is likely a defective spark plug tube O ring. I understand they do go bad on Minis. It looks like this is a "valve cover off" job, but nothing too crazy for a shade tree guy? 13 bolts, a few harness unplugs, one new valve cover gasket, 4 spark plug tube gaskets ? Am I reading the situation right ?

Last thing on my list is the serpentine belt - it's not guilty of anything anymore, but given the age of the plugs I figure I'd better at least check it.

 

No MINI experience but with another car with spark plug tubes that fit down in the camshaft cover the tube o-rings started leaking. The engine was a flat 6 so the spark plug cavities didn't fill with oil but oil leak sign was showing. Tech told me when he removed the spark plug tubes the o-rings were just shot. In pieces. They suffer from exposure to oil that doesn't circulate all that freely past them and as the oil accumulates miles and becomes more acidic the o-rings suffer. The ones in my car's engine lasted a good while most likely due to the fact the car received regular use -- and no short trips -- and I changed the oil every 5K miles. God only knows what would have happened had I adhered to the factory's oil change schedule of 15K miles.

Rather than check the serpentine belt I'd just replace it. The car is used and who knows how long the belt has been in service. With a used car I like to bring all service items up to date. Replacing the old belt with a new one is one of the easiest items to bring up to date.

Check the old belt for odd wear. A sharp edge is a sign the belt is not tracking properly. A sharp edge means a new belt but also you have to work out why the belt is not tracking properly.

My experience is this can arise from worn water pump bearings that allow the water pump pulley to be pulled out of position. Doesn't take much.

Cracks across the ribs are normal. But there should be no sections of any of the V ribs missing.

 

"I imagine the issue is likely a defective spark plug tube O ring. I understand they do go bad on Minis. It looks like this is a "valve cover off" job, but nothing too crazy for a shade tree guy? 13 bolts, a few harness unplugs, one new valve cover gasket, 4 spark plug tube gaskets ? Am I reading the situation right ?"

Yes, change the valve cover gasket; torque bolts to 90 in lbs. RTV sealant required where bearing bracket meets the head. You'll see it when you pull the old one off.

 

Well, we went from 18 codes to none. Battery, plugs, coils, filters, oil, lots of bulbs in unexpected places (fender trim among others).
Last thing was a slight ticking that bothered me, nothing like a death rattle, but there... The serpentine belt looked perfect upon inspection on the car initially.
As RockC pointed out, I took it out anyway because it's an easy job (after a video and with the right tool) and while it looked fine and not really cracked, there was some crap in some of the grooves, looked like small particles of glass or rock...
new belt, the car is sounding fine to me... Whatever tick tick tick is left I believe to be injectors. Reset everything and zero codes came back. It runs smoother and the kid learned a few things ! Now he needs to learn how to use a clutch without snapping my neck ;-)

I still notice a slight "woooo" from the right front at 70+, but I did not sense any bad wheel bearing play while moving the wheel on the lift... Might do that also just because,,

 

I can feel you.

 

Had the same issue with my 2011 Base. Changed the valve cover gasket, torqued properly. Thought it was fixed. Not at all. Changed the PCV as they can be a source of issue like this but not in such large qty, but it is easy to fix (you don't need to replace the entire valve cover like MINI says you do).

I cannot find anything at all causing this issue. Though the oil in mine was in the well of that left side center bolt. Finally, after much research and a few other symptoms that indicate a vacuum leak (nothing is leaking that can find, hoses and the like that is). So I finally broke down and bought an aluminum valve cover and will replace the gaskets and new cover. Hoping there was a crack in the valve cover I can't find and this will solve my issues.