My 92 Hatch is leaking coolant as it warms up. The leak is just below the radiator cap, but it is not the cap. I have tried a few molds on the outside to get it to stop but it will not stop leaking. I am looking to put in some sealant from the local auto parts store but have never tried it before. My questions is, have any of you ever tried the solution you place in the radiator fluid, let the engine run, then drain it and refill. Does it work? What are the risks and what kind do I buy. I can follow the instructions but I wasn’t sure if it will be a safe and permanent fix. Thank you.