have you got the 4 cyl or the v6 2.5lt ?? If it is the 4cyl it is the timing belt .slaping against the timing cover. the belt needs to be replaced, before it jumps a tooth. The 4 cyinder have a belt for timing and the V6 have a chain. if it is the v6 then it's like the other guy said it is the hydraulic tensor leaks off . it needs replacement IT IS ONLY AVAILIBLE AT A FORD DEALER > BIG MONEY. they want 120 Canadian
4cyl you can adjust the tension manualy . you need a small allen key and a wrench . but if is realy loose you should replace belt.
