How do I know if the fan clutch is bad?Wiggle it. Standing in front of the car with the hood open, grab the top blad of the fan and try to move it toward the front and rear of the car. If there's more than the tiniest fraction of an inch of play in the clutch in this direction, it's time to replace it. Also look around the shaft of the fan clutch. If it looks greasy and dirty, that's the silicone oozing out of it, indicating it's time to replace it.