1988 honda civic overheating?

we have replaced the thermostat and flushed the coolant and bled the system. while flushing and checking no leaks and no overheating. i test drove it 4 miles and the temp gauge stayed right where it did during the flushing and leak check. i stopped the engine for 5 minutes. when i tried to start again it was hard to start and when it finally did it smoked a lot and the temp immediately redlined within two miles. any suggestions to this problem?