I believe it is recommended to draw a vacuum on the cooling system before refilling, but you can also bleed the air out the old fashioned way.

 

How does this pull the old coolant out of the block?

 

Its for pulling air out and refilling.

 

Notice, it doesn't pull any of the old coolant out of the block, only air!!!

 

This is my procedure that I have used for years:

1) Run the vehicle to normal operating temp, with the climate control set to "HI".

2) Drain the coolant, and remove thermostat. Note: removing the thermostat assures full coolant flow through the system.

3) Refill system with distilled water

4) Run vehicle about 10 minutes

5) Drain system

6) Repeat #3-#5, until the coolant drained is clear. This assures that all of the old coolant has been flushed, and the block only has distilled water.

7) Install new thermostat, and O-ring

8) Fill system with concentrated coolant (NOT premixed).









Initial drain:









After 3 flushes:









After 5 flushes:

 

If you just drain once, and pull a vacuum, make sure you use the pre-mix coolant. Since the old coolant will still be in the block (which should be 50/50) adding the concentrated coolant will make the coolant mixture higher than 50/50.