1999 Ford Escort car stalls after running

I have a 1999 Ford Escort 2 liter with 150,000 miles. Recently my car has begun to run hotter than normal and has developed a stalling problem. When the engine has not been run in awhile the car starts up just fine and runs great for about 10 minutes of regular driving. The temperature gauge then climbs to a higher than normal engine temp and the car begins to run rougher especially if I come to any sort of stop. Eventually the car will just die at a stop light or sign and has trouble starting back up. After it does start up, the temperature gauge jumps to hot and the car runs very rough and you can catch a whiff of coolant. Also when it gets to this point there is some sort of rattling sound that begins when I accelerate. If I come to a stop and put the car in neutral it seems to help with the rough idle but it still sometimes dies. So far I have replaced the thermostat and the ECT sensor with no effect. The check engine light has not come on and I was told that if the engine light does not come on then a code reader will not detect any error codes so a code reader has not been run on my car, is this true? Also my heater is not working in my car, if you turn it on it blows hot air for a few seconds then blows cool air. The AC works but it causes the car to idle roughly. I have no idea if the problems are connected but they are all there.