Making an old router quiet again

The small 40 mm fan had been rattling for months. Instead of hunting for an identical replacement I tried a passive aluminium heatsink, a little thermal paste and better airflow around the case.

After a week the box idles at 47 °C and peaks just under 60 °C during nightly backups. Good enough, and the room is finally silent.

Things I would do differently: measure the clearance first, and do not trust self-adhesive thermal pads from the bottom of a drawer.