The white goo is caused by moisture. It is a common problem with the 4.0L. If you check in the air filter box, at the bottom inder the filter will be a breather element. Make sure it is clean. Also, the rubber hose that plugs into the side of the airbox and goes to the valve cover may be plugged and need cleaned.
Let me know if this helps.
Tuesday, January 6th, 2009 AT 4:56 PM