I am used to my 2014 MINI Cooper making some noises if I turn off the ignition and sit in the car for a couple minutes. Never really been sure what it's doing--maybe resetting some defaults if I've switched driving modes?

But in the last month or two I've twice sat in the car for a minute or so after switching off the ignition and heard a clear thump from under the hood. Strong enough that I could feel the vibration inside the car. What's up with that? It's been cold, if that's any clue.

 

It sounds to me like you threw a rat for a ride jumping into your radiator fan. Hopefully someone else on the forum can give you a better answer!

 

Sounds like metal expansion / contraction (maybe the cat convertor or heat shield...etc. I would ignore it for now.