Noisy baseboard radiators - could this be why?

One of our hot water cast iron baseboard radiator zones runs through three different bedrooms on the second floor. When it gets really cold outside, and this zone is running, we always hear a loud banging/rubbing nose in one of the bedrooms. The zone has been bled and is free of air, so I'm pretty sure the noise is due to thermal expansion of the pipes. I noticed that where the line comes up from the floor, the pipe is really tight against the floor boards (see pic below). Could that be causing the loud noise (even though the noise seems to be further down the zone)? If so, how can I alleviate this issue - just cut the hole a little wider using a dremel?

https://imgur.com/a/s90Yd4M

 

e,
With the limited info it very well could be. Copper pipe must have room to expand when heated. That would be a good place to start.

Hope this helps a little.

 

Is that rusty metal laying on the copper pipe?

 

beelzebob, no that's not touching the pipe, just looks that way in the picture. there's an inch or two of space (and i think it's a chunk of plaster, not metal).