Recently did a D16a6 swap, Motor runs really good, no oil leaks from the oil pan or tranny. But I had this stupid coolent leak, it was leaking from a little hole next to the radiator drain plug. I've dicked around with JB weld and silicone neither worked because the coolent continued to leak and the JB weld couldn't cure. Well tonight I looked a lil closer at and all I did was turn the damn plug 180 degree and no more leak.
Further detailed in this achieved thread.
https://honda-tech.com/zerothread?id=744515

 

had the same problem for a few minutes, i discovered( after pulling out the drain plug like a moron and emptying the entire radiator on my head) that the little o ring at the end of the plug covers off the whole, actually i think its where you drain the radiator while flushing the cooling system, oh well live and learn. lol