So my 2010 MCS just hit 50k so I decided to swap out the plugs for piece of mind. All 4 plugs had the ground strap connected to the electrode by a thin strip of carbon, with a heavy breath it blew off the plug. I've never seen this before. Any ideas?

 

Not on the tips like that. When I pulled mine out there were dirty but did not have a thin carbon build up above the electrode. Have you had your MINI carbon blasted on the intake ? Wonder if its access build up ?

https://www.northamericanmotoring.co...-cleaning.html

 

The plugs are recessed into a deep well, I believe. I change plugs on Ford cars and trucks all the time, and the plugs sit deep into the head. Yes, I have changed the plugs on my MINI, and I did the same as Ford recommends....remove coil, then using compressed air, blow any debris from recessed spark plug holes before removing spark plug. Maybe you didn't blow the debris out of the hole before removing the plug, and it picked up some debris on the way out? I have not looked at my Bentley manual to see if it advises the same procedure, but I would assume that it would include that info. Just an idea.

 

No the sp holes were actually emaculate. I was impressed how clean the plug holes were. The car has never had the valves cleaned with walnut blasting. Local dealer wants $600. looks like I will have to see if anyone local to the charleston area can assist.

 

That DIY is linked above, I would at least have them checked for carbon build up.