Mix 25% antifreeze with 75% water. A small system like this will only need about
a pint at the most, and allows plenty of spare for topping up. Use a small jug, or a funnel. Pour very slowly, allowing the air a chance to escape.
Once the system is full, switch on the pump for half a second, then off again.
This will make some large bubbles find their way to the filling line. Top up
the system again, and repeat until the system is filled up.
When the big bubbles have all been bled out, there will still be clouds of
tiny bubbles, which do not rise up through the tubes. When you have reached
this stage, leave the pump running with the filling tube topped up and uncapped.
The bubbles will find their own way out in a couple of hours. You will be able
to tell if there is still air in the system by the noise the pump makes.
