What you say about it not taking as much water as expected is what I thought too when I refilled system. Did the process as directed in 80-90 forum, but even days later I could hear air as it circulated through the radiator when engine was first started. It went away eventually, with a top up of neat anti-freeze.
Unlike the reason/cause for having to do it in the first place. The whole cooling system froze solid during the really cold winter about 3 years ago.
Couldn't understand why until my wife informed me that whenever the system was low she'd topped it up with plain water. :shock: :roll: Whit?????
Anyway she was lucky that when it thawed I was able to drain system, refilled it with water to check for leaks, with just a small weep from radiator. Drained, added Radweld, refilled, bled and all weeps OK.
She won't be adding neat water again that's for sure. She's been telt.