We recently moved into a 31 yr old ranch house and this problem is driving us crazy.
Every time the heater comes on (and now a days it is frequent) we get these clunks in our master bedroom near the air outlet. I also found it is there at various other spots as well, throughout the house. They continue to come even after the heater is off (as long as 4-5 min. after it is stopped)
I went to the basement (70 % finished) to see where is coming from and I can see it is coming from the end of the big pipe that is going into the room floor.
How can I dampen or eliminate this noise?? Is this a common occurrence?
Your help is much appreciated - Thanks in advance.