K-series running too hot - how to test the radiator fan?

[Matt UK]

Afternoon all,

Having taken the engine/gearbox out I'm not ready to get the old girl back on the road.
Having put it all back to together I'm having an issue with the car running hot - k-series engine.
At idle the car is running hotter than it used to - it will work its way up to about 100 degrees and then stay there (before I shut it down).

I'm convinced that I now have most of the coolant back in - about 4.5 ltrs. Is there much more to go in? Do I have an airlock somewhere?

Also the lower rad/hoses are not getting hot - is the themostat not opening up?

Finally I've also noticed that at the radiator fan doesn't kick in either even at 100.. is there a way to over ride this to check that it's actually working?

Sorry for so many question, but it's annoying really; this car has always held perfect temperature whatever the conditions and even when left to idle after a session on a hot track day the needle rarely moves.. Knew I shouldn't have meddled...

Any ideas?