Engine is Running Hot?

My daughters 05 Civic is constantly running hot. She said that it started when she hit a pot hole, doubtful.
I took the over flow reservoir off and cleaned it out since I suspected that she used too much stop leak. I have put in some Prestone Super Flush today. As it idles, the temp goes from normal, to real hot real quick and begins to blow out the reservoir cap, and starts spewing. I drove it for 20 minutes and the temp gauge went to the limit, crept back home and tried to cool it down, eventually turned it off. I hadn't notice the fans running before unless the a/c was on but the fans were running today without the a/c. I bough a new fan switch, but now not sure if that is the problem or not.
Any advice is much appreciated.

When I start my car, and turn the heater on, the temp in the car rises, to where it is almost red, and the car doesn't heat. I was also having cooling problems, where the car was running hot, but I changed the thermostat, and it doesn't seem to run hot unless I'm standing still for a couple of minutes

My coolant was down about half a gallon, it's running fine now. I had a pressure test done which was negative. Any reason why it would be down?

I had it done by a garage, I don't know if they bled it or not

My Honda Civic Lx is running hot what's wrong could the sensor cause the problem

Engine is running hotter than normal, temp gauge rise
when car is running, drop down at a red light.
Any thoughts?

Joe

I have a 2000 Honda civic it is running hot and I have rusty water coming from the resavoir and the hoses. I had the radiator flushed and the thermostate changed along with the two hoses that busted had the engine cooling fan changed and the thermostate cap changed. After that The problem went away the rusty looking water went away and the car was running fine. Almost a 3weeks to a month later the rusty water is back and my car is running hot again I keep adding engine coolant and letting it cool off but I don't know what else to do now.