Question about coolant level on 3VZ

[thaharlequin]

Will draining the coolant from the radiator drop the level in the block enough for me to knock out a freeze plug and install a block heater, or do I need pull the plug in the back of the block?

[mazdaverx7]

i'd pull the block drain plug. when the engine is cool and not not running, the thermostat will be closed. so when you drain the coolant from the radiator, none of the coolant from the engine will be released into the radiator to be drained due to being blocked by the thermostat.