"Gong" sound from my insert--what is it?

This is new this year. Sometimes after about an hour after starting the first fire of he morning I hear a pretty loud "gong" sound from the insert. I assume it's the liner and the cause is contraction after the initial high temps. Just heard it again today about three hours after starting a warm box.

Any ideas what this might be?

Hi, our Super 27 makes a "gong" sound often. I can tell you the flue temp. (range) when it starts. At 500* to 600* and back down. Our installer told us this is normal, then again, in our case its the wood burner itself. Are you positive that its not burner and is the liner?

I agree, it is being caused by expansion and contraction of the metal. My SS chimney cap does the same when it heats up. You need to try to figure out where it is coming from though.

My fireplace gongs too. I'm used to it. Does it about 10 minutes into morning restarts.

i used to watch the GONG show....does that count? (those are hours of my life i'll never get back). probably do to expansion and contraction.

cass