>>>*Drop me an address to my email address (engnbldr@engnbldr.com) and I will drop what we use in the mail, I assume you are in the USA?

It is a commercial sealer machine shops use to stop exactly this little problem and some others, we call if Magic Seal.

It is for pinholes, cracks and tiny leaks like you describe.

It is a little cube, just break it up, drop it in the radiator and run the engine fo a good half hour, the leak will be gone.

*No concerns at all with plugging anything, I have used it for over 20 years......*EB

*Beats the he** outa me!....*LOL**...