2007 i-CTDi thermostat change

[JapCar]

I didn't find any thread regarding thermostat change. I need tho change the thermostat because the engine temperature is not steady, it depends of loading. I mean the temperature gouge needle is about 4 o'clock when engine is fully warmed and under load but drops when car goes down hills, so I suspect thermostat is blocked at open position.
I didn't find You Tube clips about this or any guide how to change the thermostat. It is not easy accessible and the job seems not straitforward.
Where drain the coolant from- from lower radiator hose or there is **** on the radiator (where)?
Is there air escape valve when filling coolant (where)?
Any advice will be appreciated.

 

[OB1]

Coolant is drained from the bottom of the radiator - its a plastic plug or wingnut type thing if I remember correctly. Can't remember if there is an air escape valve on the pipework.

 

[JapCar]

Coolant is drained from the bottom of the radiator - its a plastic plug or wingnut type thing if I remember correctly. Can't remember if there is an air escape valve on the pipework.

Thank you. I already did it. Now the engine gets worm twice more quickly. The old thermostat was 2mm open...