hydronic baseboard heat water pipe noise

[1 FMF]

any thoughts on what would cause my baseboard heat to get air in it and make for water trickle/flow noise when the heat kicks on and water gets pumped through the baseboard heat?

what's happening is I'll be upstairs and after 11pm the heat will kick on and I'll hear water flow through the baseboards in the bedroom. It has air in the system. This seems to be happening the beginning of each winter when I start using the heat again. What I just did, and have down for maybe last 2 or 3 years is purge the baseboards and furnace. After I do that, everything is great and quiet for the rest of the winter- december to may.
So it only seems to be happening after not using the heat for extended period of time (over the summer).

 

[fdcg27]

Do you have a closed expansion tank?
You probably do.
You have residual air in the system, and it will take reapeated bleeding to get it out.
Once you've done so, the system will be fine until you have some need to open it.

 

[Donald]

You should have an air trap and a float valve to get rid of air. The float is probably crudded up. Replace it, its cheap.