Tomorrow I am supposed to help a friend install a new Thermostat since his other one is stuck open. I am a new wrench so I overlook things quite easily. Do we have to drain the entire radiator or can I just take the hose that connects the radiator and the thermostat housing? I know the fluid in the hose would come out but am I missing any other flaws. Do I need to un-pressurize it and how (plus repressurizing)? I am youthful but I really want to learn, so any help is appriciated.

 

You don't have to drain the whole thing.

 

don't worry about depresurizing. just make sure the engine is cold. when u reinstall the new thermostat. run the engine with the cap off for about a min or two to let all the air get out.