I put a new performance radiator in my CJ7 10 years ago. Fast forward to now... I pulled the plug where a drain petcock should be(?) and drained my coolant. The plug goes back in tightly, but coolant leaks past. I don't remember why I originally put a plug in. Should I have installed / soldered a petcock in when I bought the radiator 10 years ago? Is there something that I can wrap the plug in to make it seal? There are no threads in the radiator plug hole. Before today, I was pulling my lower radiator hose off (and now suddenly remember why...) to change my coolant.