[bb123]

This is due to a phenomenon called heat soak which is where the engine temperature increases above normal for a time after it has been switched off due to the lack of coolant flow. The fan is coming on to aid cooling the engine/engine bay to reduce the effect of heat soak. With carburettor fed engines it is sometimes advised by the manufacturer to allow the engine to idle for some time after running it at high RPM. This is because the effect of heat soak can be significant enough to boil all the fuel off in the carb, making the engine hard to restart when hot.

[op00to]

I had an old Volvo that would “vapor lock” on short trips. It’s amazing how reliable cars are now compared to 20 years ago.

[rootusrootus]

In my experience it was more than 20 years ago that this happened. It was when most cars switched to fuel injection. Late 80s, early 90s. Treating a car as an appliance and having it 'just work' became so much easier when fuel injection was invented.

20 years ago was 2003, which is practically yesterday [in my mind...].

[bratwurst3000]

To my knowledge it is because the the oil and water needs the motor on to move through the engine and cool certain parts . If the motor is shout down to early and those can’t circulate anymore following could happen

-turbocharger overheats

-oil overheats And the things you stated and much more …

Better to let the motor run while standing is to run it the last kilometers in low rpm

[l33tman]

same issue with projector lamps, the fan is kept on for a while after you shut them off

[HPsquared]

And ovens.

[almostnormal]

And some PC power supplies.

[krallja]

My portable induction stove runs its fan for a minute after I shut off the coil.

[actionfromafar]

Also turbo charged engines can greatly benefit from running idle for a minute. I learned the hard way. (Had to replace the turbo.)

[rainbowzootsuit]

There have existed "turbo timers" that keep the engine running for a short time after the key is off to help avoid this. Not sure if that works with modern cars as easily.

[rootusrootus]

Modern turbo designs (most anything in the last 25 years, at least) use water cooled turbos and convection keeps the water flowing after the engine is turned off. This is why we don't use turbo timers any more.

[gambiting]

And also even back then it affected almost no one, there were loads of tests done on this by automotive magazines of the era and found out that usually the last 1-2 minutes of gentle driving to your driveway/garage is more than enough to cool down the turbo properly, the only people affected were those who due to either aggressive driving or circumstances of their location would drive at high rpm, stop, then immediately shut down their engines.

[actionfromafar]

Towing something heavy uphill, then stopping to get some gas and a sandwich. The SAAB killer move.

[FireBeyond]

I have a 2021 twin turbo car (Audi RS 5). It runs the radiator and pumps adaptively on engine shut off to bring things down.