Radiator noise AFTER vent

Doester

Hi guys!  So several of 2nd floor radiators start going “clink clink clink” immediately after the boiler shuts down and after they pull air in through the vent.  

Of course the one in our bedroom is the worst, and lasts a few minutes. (One clink every 30 sec or so)
It’s sounds they go into vacuum and slightly reverse hammer?  I have one pipe steam. Any suggestions on things to check?  

I ordered some vent-rites to play with more/less venting. Currently I have Hoffman 1A vents set really low, but they are finicky to dial in.  

 I put bigmouths on the mains, so I assume they are sufficient.  

Thanks!
B

Jamie Hall

Much more likely to be an expansion noise -- or, more accurately, a contraction noise -- as the radiator cools.

A little odd to have it on cooling and not heating, but... not that unusual. As well as the more or less obvious, like making sure the feet slide easily on the floor, if the radiator has tie rods see if one or more of them is just a bit loose. They should be snug, but no more than snug, when the radiator is cold. If there is a lot of paint on the threads (now how could that happen?) be very careful about trying to tighten or loosen them -- they are amazingly fragile.

mikeapolis

Is this a first for the radiators? Are they level not pitched? Calcium buildup on the Hoffmans? Waterlogged radiator?

ethicalpaul

I think it could be hammer. When I had my Big Mouth hooked up, I think I recall that it was very slow to open at the end of a call for heat, which caused all the air to get sucked in via the radiator vents. My memory is fuzzy on this but I think I had a similar situation as you describe. Is the slope of this radiator OK?

I ended up taking the BM out of service because it was also slow to close on steam, and the issue seemed to go away then.

You could try a different vent on that radiator, maybe one that stays closed longer, or you could try a different main vent on that main as an experiment.

Doester

thanks guys, rods seem tight, and it doesn’t really sound like expansion but I’m typically wrong, so I’ll check it out!

 pitch is pretty good, I’m wondering if there is 150 yrs of gunk blocking water flow in them. That’s a possibility. 

I’ll also assign my kid to stand in basement and notify when the BMs open so I can see if they are delayed. Thanks for ideas!  I’ll report back.