Can anyone tell me if it's necessary to drain the radiator and bleed the system to change the T-stat on a 2011 g37 3.7. Thank You for any advise.

 

you will loose coolant when disconnecting the lower radiator hose to the t-stat.

you might as well drain the coolant & refill while you are at it.

yes, you will need to bleed the system since you open the system to introduce air in the system. use the lisle funnel for easy bleeding & check out the coolant drain DIY on bleeding from the radiator valve too.

gl & share some pics of how you change out the t-stat for the next person.