Strange noises while pressing the brake and after switching off engine

My water pump was changed recently after a bearing started failing. After getting it from the mechanic, I had to refill the engine coolant system properly since they had not bled the air out (thank to Patrick and others for advising me to do so). Now the radiator is full to the top.
However, I still hear strange noises in two settings. First, when I switch off the engine after driving for a while, I hear a hissing/rattling noise around the area of the water pump (one of the attached videos) - it goes on for 10 minutes or so. The second, is sort of tapping/light clicking noise when I drive and stop at a red light (sometimes also when I pull off after stopping), it comes and goes and the recording of that noise has other street sounds, but the noise is still recognizable (the other video). Please let me know if you have any suggestions what these sounds might indicate.
https://photos.app.goo.gl/a3hoSprrRUzXMwjZA
In the way of background, I had a body repair of the front passenger side after I was hit lightly in that area a few months ago. That might have been the trigger for the subsequent water pump failure.