Changing car's coolant?

I want to change the coolant in my car. Can I just undo the petcock at the bottom of the rad and run the engine for a couple of minutes and let all the coolant run out and refill? or would this do harm to the engine?





If not what is the best way to drain the system. Keep in mind I%26#039;m an ok do it yourselfer.|||Don%26#039;t run the motor while the radiator is being drained. You stand the chance of overheating. If you want to make sure that you get it all out there should be a drain plug in the side if the block near the bottom. Each vehicle has it in a different place so it is hard to tell you exactly where. ( if you have a V8 or V6 you will have one in each side ) Just drain those and refill and you should be fine.|||yes do that but have another person filling it up at the radiator till the bottom water comes out clear, then turn off drain it all out refill with 50/50 or coolant and distilled water|||better not risk running it w/o coolant. just drain it by gravity and be sure to go back with distilled water to keep from getting gunk in your system|||the proper way is to leave the engine off and undo the bottom radiator hose. let the fluid drain out into a bucket because antifreeze is dangerous and against the ordinance in most cities to just drain onto the ground.





anyway, open the cap and use a hose to flush out all the crud that built up. then when the water coming out is clear, reconnect the hose if it is in good condition (doesn%26#039;t look mishaped or cracked) and use the correct type antifreeze to fill %26#039;er back up. i would run the engine when filling up the car so that it gets all the air out. when the fluid stops going down, close the cap. make sure the overflow is at the right level.