you need
  • - battery,
  • - key,
  • - bucket.
Find the top end of the radiator drain valve or a valve for venting.
Put a bucket under the battery in order to avoid spilling of water, otherwise you can not just create a pool, but also flood the neighbors if the airlock will need to drain the water.
Turn the valve stem key a quarter turn.The key is to not remove the valve.Of course, if you have a valve on the side of the battery, get rid of the air pockets will be easier.
Wait until the end of the hiss, nor will the first drops of water and close the valve.