Few things I've noticed while flying:
- Setting radiators to automatic will fully close them and they'll never open, temps rocket to 130ºC and engine dies
- Setting radiators to the Open or bottom position will fully open them, usual temps around 30ºC in flight
- Closed, well, closes the radiator, temps rocket and engine dies
- Keys for Radiator Open and Closed are reversed in the control options, do the opposite ingame
- Radiator switch position on the ground while idle doesn't seem to matter, always fully open
Just something to look into.