I have a yanmar 4lha htp inboard diesel engine, and have been trying to
cange the fresh cooling water, I wanted to add a new "long term anti
freeze".

My challenge is:
The capasity is 15 litres, but I am not able to fill more than 7-8 litres. I
am afraid to run the engine hot, in case there is alot of air in the engine
main block.
The engine was cold when i filled fresh water on it, and I guess the
termostat was closed. There was also alot of dirt in the old cooling water
when I drained it. (stupid of me not to mesaure the amount I drained!)

I have been guessing on 3 causes why I am not able to fill more than half
of the engines freshwater capasity:
1 The termostat is closed and airthight, and will not let me drain half of
the old cooling water.?
2 When the termostat is closed, it will not ventilate air out as I fill the
engine with new cooling water?, I am afraid there is big airpockets where
cooling is most needed.
3 Dirt from the old cooling water will not make me able to drain it
properly.?

Any surguestions?

Aron Tvedt, in the North of Norway