is it necessary to drain the coolant in the block? im replacing my radiator and obviously need to drain that, but i was wondering if thats all. the instructions for drain and fill say to drain the block too. any potential negatives from not draining block?

 

any1? cause i already have my old rad out and im waiting to put my mishimoto in.

 

Well if it has been a year or so since you replaced the coolant you might as well do it.