Hello Ford lovers. I have a 2003 Ford Expedition 5.4 liter. I experienced a cylinder 5 misfire. first thing i did was change the coil pack due to it still being an older coil pack compared to the others and code. Truck still had rough idle and code never left. Next step, pulled coil pack and plug and noticed maybe a 1/4 of an inch of coolant in the plug port. I got most of it out put the copper fluid which was recommended by auto mechanic and truck drove fine for about two weeks. This past week code came back and rough idle returned.Also hearing a tapping noise I didn't hear before. Head gasket or I'm also hearing there is a coolant hose that leaks near the thermostat that can leak down into the spark plugs but don't know exactly which spark plugs this can affect. Can someone help me please. This past year I had a upper intake manifold changed but can't remember if mechanic did head gasket at the time. Is this something that is recommended while upper intake manifold is replaced??