my car sounds like a dot matrix printer at a stop

If it sounds like the printer could be inside the cabin under the dash, look at this thread.

If you are sure the printer is out under the hood, like on the left inner fender, look at this thread here.

 

The coolant pump sounds like a computer hard drive (the old style with moving parts) that is searching on the disks

Would a dot matrix printer sound more like a brake actuator pumping? I hope not

 

I think the coolant pump sounds like a pump. It comes on, makes a continuous uniform pumping sound, stops when it's done.

What I'd describe as sounding like a disk drive seeking, or like a dot matrix printer, is the coolant control valve. It has a position sensor on it that goes flaky. When the position sensor goes flaky, the ECM keeps seeking the valve back and forth, trying to get the right position reported by the sensor. So it sounds just like a thing seeking back and forth, because it is a thing seeking back and forth.

That was the second link in #2 above, which goes to a post with a youtube link.