There is a light brown stain/leak coming from the leading (lower) spark plug port on the rear rotor. I noticed this a couple months back and decided to inspect and replace the spark plug. At the time the plug looked healthy but replaced it anyways with the same brand and model (NGK Laser Iridium) and then cleaned off the area.

I did the brakes this weekend and while the driver side tire was off I inspected the ports and could clearly see the stain/leak had come back (attached 3 pics).

Other then visibly seeing the stain I don't notice any idling or power issues of any kind. It drives beautifully and is completely up-to-date on everything (man & diff fluid, spark plugs, coils, coolant reservoir tank replacement, oil, brakes, alignment, balance, you name it. )

Since no other plug is giving me this issue and I've replaced it and still have the issue, I'm assuming it is not due to improper torquing of the plug and if it helps, the throttle body is clean as a whistle and there are no oil leaks anywhere else.

My next plan is to go through the gigantic diagnostic manual to try to pin point this down further and then find a rotary specialist in the area if I can't do the job myself, but I'm hoping you guys might have some ideas. Thanks for any help.

[Series 2, 2009, with approximately 26,000 miles.]

 

Us the oil dripping on the lower spark plug boot and then running down there? Or does it look like it is coming out of the plug hole?