My heating system is kind of unusual. I have hot water baseboard on my first floor, 5 radiators on the second floor and one radiator in the attic.
I recently had the boiler serviced and have started using the heat. The baseboard on the first floor work fine.
Two radiators on the second floor and the radiator in the attic are also working. However, three of the radiators on the second floor remain cold.
I cannot easily bleed the radiators on the second floor because there aren't any bleed valves and the screws where the bleed valves would go are painted over. Obviously, it is unlikely the prior owner bled them. Also, because the radiators are totally cold, I don't know if bleeding will help. All of the radiators have automatic air vents (they appear to be fairly old). I did notice that the radiators made whistling noises (through the air vents) at times but did not warm up at all.
Any thoughts as to what the problem may be? Thanks!