What do i do.My car overheated and now it seems fine…

I have a 98 honda civic with 120k miles on it and was driving it on the freeway when i noticed the temp gauge all the way up. I drove it an additional 5 miles to my work and turned it off. Could not see where it is leaking from. The next day i filled the radiater with water and drove it to work ( 9miles one way) and it did not overheat. I have been driving it with water in the radiater filling it before i drive for 2 days and it has been fine. I checked the radiater itself, hoses etc. And do not see any leaks. My check engine light went on at the time of the overheating and is still on. My question is how do i diagnose the problem myself without paying labor fees to a mechanic. Just need to find out where the leak is. Thank you very much

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