Doesn't have to be a problem. Put a piece of rag (that won't tear or fall apart) with greas on in into the hole (in such a way that you'll be able to fish it out again.

I don't think very small fragments of iron will do any harm in the cooling system ?

Finn

John Slade wrote:

 > I simply threaded the hole and put in a fitting. I think 1/4" NPT. 

That's fine when the engine's apart, Finn. I don't think I want the metal to go into the block.

Looks like another trip to the machine shop - or can you buy these barbs from Mazda?