ok i am changing my heater core but do i have to flush or drain my coolant. do you have to in order to change the heater core. the coolant in my car is about 3 weeks old. also how do i drain the coolant the right way no flush but drain.

 

If your changing the core because its collapsed and is full of rust and silt, yes i would flush it and refill.
If it just burst, and theres little or no rubbish floating in it, then probably not.
Theres usually a drain tap on the bottom of the radiator, facing the engine block.
Anti-freeze isnt that expensive, so dont go the cheap way just to save a few pennies.