Putting in antifreeze

That is exactly what we do. During the mid to late 1990's, there was a common problem with the sealing surface inside the radiator cracking when the petcock was closed. That resulted in a drip of coolant about once every five seconds. The fix for that was to replace the radiator. Now we rarely use petcocks, partly for fear of that happening again, and partly because the engineers put them where they are hard to get to.