I have been over the top with preventive maintenance on my wife's 08 Cooper S since we purchased it new. However, one item that I completely missed was changing the spark plugs. I guess being so occupied with continuously feeding the engine oil that it burns like a two stroke as well as one major repair after another, the plugs slipped my mind.
So now at 133,000 miles I have a misfire code on number 2 so the plugs are the first thing to check. I started an attempt to remove the plugs and with much effort they won't budge. I'm not going to crank down anymore as its obvious they are seized in the head and the threads will more than likely come out with the plugs.

I'm considering bringing it to the dealership for the plugs that way it's on them if they jack up the head. Does anyone have any suggestions?

 

Put some penetrating oil in there and let it soak for day..

 

Make sure the socket isn't binding up on the "tunnel" also

 

I'm using the thin wall spark plug socket so no problem with binding.

 

Either way the plug has to come out, like stated above let some penetrating oil sit on it for a couple hours, it would also be beneficial for the car to be hot so as to get the penetrating oil working into the threads.

I would say that you just need to give it a bit more muscle, I've yet to see a plug break off in the head of these cars, but if you take the threads out with the plug there are repair kits made by Time-Sert. I would find a reputable local shop before taking it to the dealer though, the dealer will tell you the head has to come off and that they have to sell you a new head when they destroy the threads.

worst case scenario it should only cost you a couple hundred bucks if the plug takes the threads out of the head.

 

I have used helicoils on other stripped threads before so is the Time-Sert the same thing? I don't see how a repair is possible without removing the head wouldn't metal shavings would get in the cylinder when drilling and tapping for the thread insert?
I'll try the penetrating oil and hopefully i won't even have to go down that road.

 

Put grease on the tap when retapping the spark plug hole. The chips will stick to the grease.

 

Don't take it to the dealer. They will tell you to replace the head regardless.

 

You aren't going to destroy anything with a couple of chips in the combustion chamber, before starting it you can leave the plug out and crank the engine so it blows anything in the cylinder out before starting.