1994 Mazda MPV

Engine problem
1994 Mazda MPV Engine Size unknown Two Wheel Drive Automatic 87,000 miles

My engine over heated this afternoon apparently because of a coolant leak. My roommate insisted that we pour water into the coolant system instead of actual coolant. Is this correct? It's already done, what can I do to fix it if it was a bad idea? Also, if it is true that you should water down coolant, what are the appropriate porportions? Thank you!
December 17, 2007.

It seems that your roomate wants you to get another car by doing that-drain it back out and put a 50/50 mix in it-I hope you're not in a weather that goes down to freezing poiint 32deg-that water will turn into ice and create more headaches/wasted money thanks to your roomate suggestion.

Dec 17, 2007.