A man has three containers, an empty one that holds 15 litres, a 5 litre one full of distilled water and 5 litre one of coolant. If he pours the 5 litres of water into the empty container and adds 2.5 litres of coolant (as per instructions) he now has 7.5 litres ready to add to his fiat coupe. When he re-fills his completely empty coolant system (including heater matrix and pipes) why is there still nearly 3 litres left in the container!
Answers on a postcard.

Did this arduous task make you thirsty?

Ah, if only the man had bled the system.

Air lock?

Did my best to bleed the system, let it run up to temp with the cap off whilst periodically squeezing the hose to the thermostat. No bleeding bleed points on silicone hoses!

Because the block is full of water already. You can't drain below the level of the head, easily.

So what do I win?

So the bottom rad hose doesn't syphon the rest out? That explains why despite new coolant the tank is still a little cloudy, bum. I will drain it off again and refill it. Is there no way of flushing the whole system? I put a couple of litres of water in after draining hoping for crystal clear coolant.

Szkom, you win the right to be as smug as you desire!

You could put a hose in one of the pipes and flush it out. But you run the risk of uncovering leaks.