Originally Posted by botters

the orangey gunk is usually rusty antifreeze that has leaked from the two core plugs around the spark plugs this usually knackers both the plugs and leads so get both changed and some new core plugs fitted, just because you are getting a spark when lead disconnected doesnt neccesarily mean you are getting a strong spark
worst case scenario is you will be down on compression due to an eroded valve seat from pinking caused by oil bypassing the rings which is something that is getting more and more common in my experience with zetecs, ive done 4 this year alone