I have a 6yr old weil McLain gas fired boiler.. it has started clunking when running.. it shakes the house with what sounds like a stream hammer.. replaced expansion tank.. no relief.. old. One was waterlogged.. Temp set at 180.. hot water boiler. With radiators.. it has 3 pumps 1taco 2 grunfoss bled system on every floor. (Ex steamfitter) 30yrs... baffled?
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Hi Dickhead

Isolate the system to running only one zone at a time. Can you isolate the sound to only one zone or is the sound present all the time?

Back to you...

Mark