..is it necessary for me to drain the coolant from the engine block, via the drainage bolt? Additionaly, how do I bleed the coolant system for air bubbles?

 

It isn't necessary to drain the coolant from the block...in fact depending on the year of your car, I'm not sure if the G3s have it do they? Anyhow, in regards to bleeding the boolant system for air bubbles

After putting in the new radiator and plugging everything up....fill the radiator til it tops off with coolant/water mixture. Keep the radiator cap off and turn your car on with heater at full blast....As coolant and water disappear (due to bubbles), pour more coolant/water mixture in to top off again. Keep doing this til radiator fans come on a few times. I don't know which car you have, but my G3 took FOREVER for the fans to come on. Anyhow, that's the way I bleed the system of air bubbles...not sure if it's the most proper way but since no one has posted yet, I figured I'd give a suggestion

 

Thanks very much, I appreciate the input!

 

yeah when I swapped mines also I didn't drain the coolant from the block
and basically what BD7581 said....