I have a 2003 Dakota 3.9 that I had run hot (my fault, left the coolant cap half way "long story") while stuck in a traffic jam for around 20 minutes all the way hot. I was able to finally pull over. My dad told me if an engine is running it is ok to slowly pour water into it. So I did so and it was ok, but it would seem to boil/bubble over at times but it would never lose any coolant just fill the spill over tank. I operated it like this for about 5 years and I had to change the radiator and it stopped boiling/bubbling. It now has 215,000 and still runs excellent.