Issues relating to coolant...

1- temp not moving? = new thermastat housing replacement.
2- coolant airlock? =bleed valve open, expansion cap open, hot heater on full with fan speed on 1, , run engine til 85 temp then close bleed valve when coolant spurting out. Top up when required.
3- coolant not running through system? = water pump failed? Inspect and replace if required or airlock, refer to 2.

Any more? Add please