type control and f and do a search on radiators. Harold did a great explanation just below here. You don't say whether you have hot water or steam which bleed and drain differently. Go to the wall and ask as I said below. Radiators will last forever but sometimes they get gunked up and need flushing and the valves and bleeders corrode and get gunked up and plugged with paint and need replacing. Second floor and up is always a problem and maybe your pressures or water volume aren't right depending upon the type of system. Hot water and steam should get an annual check up by a qualified tech.