I noticed a coolant smell from time to time with the original one, but never could see a leak. (Had to add a splash of coolant maybe once every 8 months). Got it replaced as a precaution at 95k and the underside of the housing was all crusty with dried coolant. Was definitely leaking, just very slowly.You should have left the first one alone maybe. They don't suddenly fail catastrophically as far as I know, so probably don't warrant preventative replacement like a cam belt or something.