have a 2003 F-150 150K miles. will be driving along fine and suddenly no oil pressure. check level and it good. restart motor and oil pressure is there. last time it happened there was tapping from the lifters i think. shut down motor, waited a couple on minutes and restarted motor no problem. change oil and filter no metal showing in oil or on magnet. drove to town (4 miles) and back. just before I got to the house the oil pressure dropped again. there is now a ticking noise that sounds like something in the fan at the front of the motor, but the fan is clear. anyone have any idea of what I'm dealing with. Any help greatly appreciated.