anyone know about heating systems in houses?

[thefishingfreak]

it's a tankless heat/hotwater system with the huge radiators{the big square ones}closed system.
i'm bleeding the air out of all the radiators.{due to a baseboard add on earlier in the spring}

do i have to add water somewhear??????to the system??????


it's got tons of air in it.
the two radiators on the top floor are cold as ice.
downstairs ones are kickin.

thanks for any help.
it's an old house
mike