some branches of my radiator pipe tree not getting warm ?
Go to a plumbing supply house, hvac. Might even find em in the ugly Orange or blue box stores. YES you want the water IN the system and the circulator running. Ask for a vent key, vent will be on top and looks like a small nipple sticking out and if you look inside you will see a square stem, thats where the key fits, loosen it and you should get nothing but water from it, otherwise you will hear air comming out and you want to let it all out till there is only water NOT bubbly water just solid water from it then close the vent