So this is the first time i've ever tried flushing my cooling system...
I used a bottle of Prestone Radiator cleaner.

Cliff notes version:
Drained radiator, refilled with water + cleaner. Turned car on, appears to be leaking water when the heater is on. Car running hot. Whats the problem? What do i do?

Detailed version with step by step of my actions:
So I drained the coolant from the radiator via the radiator drain plug, removed, cleaned, and replaced the reservior. It was extremely dirty, so I filled the radiator back up with water, ran the car for about 10 minutes to get it up to temp (I had the heater on during most of this part but did not see any leaking). Went out to let it all cool down again before refilling. Today i wake up, drain it again. Pour in the bottle of cleaner, fill the rest up with water. Opened the bleeder screws before turning the car on, some bubbles came up out of the radiator fill cap and the level lowered some, kept topping it off until it stayed full. Closed bleeder screws, turned car on. Opened bleeder screws until no bubbles came out. Turned heater on, looked under car, car is leaking water (i suspect if the car had coolant in it, it would be leaking coolant). Turn heater off, few drops continue but after a couple mins it practically stops. Turned heater on, steady dripping. Turned off, slows then stops.
By this time the car is warm, but the heater is not really putting out a lot of hot air, a little warm, but not hot.
The car got up to half way between the half way, and 3/4 mark on the heat gauge before I turned it off.

I searched but couldnt really find something that fit this description, from some of the threads I read, it sounds like I may need a new "heater core". Is this driveable the way it is to get me to and from work? It is a 15-20 minute drive that is about 12 miles.
Would the 'heater core' problem, if that is what it is, be causing the car to get hotter than normal? Is having the "cleaner" and no coolant in the radiator going to make it run hotter? A friend was trying to tell me that it should not, as "coolant" does not make it run cooler, it just changes the boiling/freezing point. I decided to flush the system because it was running hotter than I was comfortable with (hanging around the 1/2 way mark). I'd very much prefer it to hang around the 1/4 mark.

I also tried to replace the thermostat as I have a 160 hypertech, but after removing thermostat housing screws, I discovered that when my water pump was installed they used some type of sealant on the housing, and it seemed to be stuck pretty well to the water pump. It is supposed to just lift off once the 2 screws are removed, correct? I couldnt get it off and gave up, deciding I would get it off before I put coolant back into the system as I would have more time that day.

 

Running with no coolant is not a good idea, all the water will start to boil off. plus coolant has rust preventative addatives that Need to be there. Its summer time go to autozone and get a connecter to bypass the heater core for now

 

Take it to Radiator shop and have them test it out. Could be bad radiator or a bad heater core (they both will leak). It's often difficult to see where the leak is unless it is under pressure---so have the shop put it under pressure and go from there.JMHO