Calorifier problems

[Trundlebug]

When I had similar symptoms to those described above, I had an air lock in the calorifier coil.
Need to blast through the coil with water from a hose or something of similar pressure, to absolutely ensure there is no air in the coil.

Yes, I had hot supply and return hoses as well, didn't make sense. But rule this out before proceeding further

 

[Karlsenkystfiske]

You would think that the engine cooling would be strong enough to displace any air in the coil?
Anyhow: What was the clue here??