Since I bought this Explorer (4.0 OHV) for my daughter who puts 3000 miles on it a year, it has consumed antifreeze (a pint a month) but never see it on the drive way. Also, I have had cylinder #4 sparkplug foul a couple of times this year. When the engine is on, you can smell burnt antifreeze in the engine compartment. I finally have seen a spot on the driveway and antifreeze in the engine mount near the front. Question is, can it be an external head gasket leak or freeze plug? No codes are displayed and it runs great besides all of this.

 

Try head gasket. Freeze plug will NOT foul the spark plug.