so since winter time has been rolin around i been keepin up more on checkin on the car (2000 Gt) and makin sure all the fluids are full and ok.....so a week back a checked the oil and it was about a quart low no biggie so i added a quart.....went around didnt drive the car for a couple of days start it up and i hear a slight tap comin from the engine (70,000 miles).....so i didnt think anything of it drove around...car runs smooth no problem....warms up and its gone...next day does it again for like 2 seconds and goes away.....day after nothin at all....now its back......what could it be......oil is full....and even with the tap i drive and the car is smooth as ever