What is happening with my water pump?
 

2018 CX9 Touring: My son in law changed my water pump Tuesday and car worked perfect. Purred like a kitten. By Thursday, continuing to run great but I noticed that I could hear something still running for about 10 seconds after the car was turned off. That was the first time the car ever did that. Now today, my son was on the interstate and suddenly got a message to pull over and stop the car or risk serious engine damage. He immediately pulled over and turned the car off. He said a sudden rush of hot air filled the cabin. We had the car towed to a shop, but they won’t be able to look at it until Monday. Anyone here want to throw out a guess as to what it is in the meantime??

How many miles on the car?
What was the symptom that led to changing the water pump?
How was the decision made that the water pump was the cause of the problem?

The sound of "something running" could have been the electric fan. This is normal when the engine is hot.