in our home we have small baseboard radiant heat. The baseboards are cast iron and do hold the heat in the house pretty well.
I have noticed in the last week that from one of the pipes, at least I believe it is coming from one of the pipes within the baseboards, there's a very loud whining that lasts for several minutes then it stops.
I have walked around and bled the pipes. I notice it mostly when it is pretty cold in the house and I turn on the heat. It seems to be coming directly from the boiler itself, possibly.
It is an older weil-Mclain boiler.
I'd really appreciate any advice that you might have.