One problem related to engine head gasket failure has been reported for the 2004 Ford F-150. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Ford F-150 based on all problems reported for the 2004 F-150.
"condensation" in the engine block. After finding water in the oil of my vehicle, a 2004 Ford f150 with the 5. 4 liter engine, I took it to the dealership for head/head gasket repair assuming the water was antifreeze coming from a failed head gasket. The mechanic at the dealership identified the water in the oil and told me that this comes from condensation in the engine block and that it is a normal condition in all f150s with the 5. 4 liter engine. I don't know if this means only those built after 2004, or all. Water in any engine is not a good thing as it causes corrosion, breaks down lubrication, etcetera. Potential failure would be that the engine could prematurely/unexpectedly fail, stranding the driver and having a huge cost implication for the owner who would likely have to have a remanufactured engine installed at their own cost since the failure is likely to occur after the 3 year/36000 mile warranty has expired. Nothing at all was done to correct this defect.