Originally Posted by east tx skier
Definitely drain the block and manifolds before adding antifreeze. No dillution problems and you will use less antifreeze.
My only issue with draining the block and manifolds is that if you take the hot water way from the thermostat long enough for it close you wont get anti freeze through out the motor.
I did a test this time, when I winterized.
I ran the motor to temp and let it run for 15 minutes at temp. Then drained the oil and changed the filter. The oil was very warm so I knew the motor was good and warm. After changing the oil I ran the motor back up to temp and let it run for 15 minutes once it reached temp. I then ran 6 gallons of anti freeze in through the water pick up. Once done I pulled the side plug to check for anti freeze and it was full of anti freeze and no water.
I think as long as you full heat the motor and do not let the thermostat cool down you are just fine not draining the block and if you do drain the block and wait add anti freeze the thermostat is more likely to close. Likewise, if done correctly I do not believe there is any reason to pull the thermostat.