Why when I drain the antifreeze from the car the check coolant level want come on?

You don't have to drain the system to replace a sensor, but if you're just draining the radiator and engine, there's still coolant in the reservoir. That's where the level sensor lives.

You said you changed the temperature sensor, not the level sensor. Did you drain the coolant in the reservoir? If not, the level in it is not low and the light won't turn on. To test the circuit, unplug the level sensor in the reservoir and use a stretched out paper clip or other piece of wire to short the two terminals in the connector together.

The level sensor just reports what's happening, it doesn't cause other problems. Most cars don't even have a level sensor.

If the engine is overheating, check for proper operation of the radiator fan and be sure the radiator isn't blocked with debris. If that is okay, have a combustion gas test performed by your mechanic. That involves drawing air from the radiator through a glass cylinder with two chambers partially filled with a special dark blue liquid. If combustion gases are leaking into the cooling system from a leaking head gasket, the liquid will turn bright yellow.

You may have damaged the heads by overheating the car. Go to the parts store and do a hydro carbon test on your coolant to test for blown heads or gaskets. Thanks for using 2carpros

Sorry caradiodoc may bad.

"Just don't let it happen again" he said with a sarcastic grin.

:)

Carry on.

Yes but youll have replace the heads that have cracks in them. Youll need 2 rebuild heads and a head gasket set plus labor.