about a week ago after replacing my head gasket i flushed my cooling system(leaving the heat on to clear the heating block), but when i tried to turn on my air hot air still blew out. it used to be cool, not ice cold, before. it was last recharged in early 2000 mabey 2001. does it just need to be recharged by now?

F.Y.I. when i took of the head i had to undo the air pump hose and even though the airpump is new, the air check valve is as old as the car.

p.s. the car isnt being driven right now and i was wondering how often and how long should the car be ran to keep everything, mechanicaly, in working order. i was going to run it every 2 weeks until it reached operating temp.

one last question my egr valve is rusty, should i replace it or leave it alone and at 200,000+ miles do i need to do my o2 sensor?