Radiator drain plug SUDDENLY leaked!!! All fluid on garage floor.

[rino]

Early this morning I was greeted by the surprise of finding a large puddle of fluid right in front of my '79 240D: the radiator drain plug all of a sudden leaked and fluid is no longer visible inside the radiator.

Now, isn't this strange? Not a fluid leak during my over three years owning the car and now, out of the blue moon, all that radiator fluid on the garage floor overnight...

So, my question is, is it just a tighter drain plug I need, or should I be concerned about some potential major problem that might have caused the sudden leak?

I tightened the drain plug with a screwdriver - not realizing that the plug is made of cheap plastic - and in the process split it in a half (it still holds the fluid though).

I need to drive the car ASAP and have no time to drain and refill the radiator... What should I put in - suggestions, please? I heard that distilled water mixed with some strongly anti-rust anti-freeze is best. What product do you advise?

Thanks so much,
Rino