I noticed that in some cars (even new ones) the cooling fan stays on for a minute or two, even after the engine has been turned off and the key removed. This caused me a little bit of curiosity —keep in mind I’m not very car-savvy— so I wanted to ask: Why is that?

I see, but why not let the engine cool by itself? Because the way I see it, its temperature would drop slower and more gradually than with the fan on. Which wouldn’t seem to matter since the engine wouldn’t be generating more heat.

It’s a function of the fan being controlled by a thermostat. There probably would be nothing wrong with letting the engine cool “by itself” (which is what happens if the design removes power from the fan when the ignition is off), but since the normal operation of most cars is to run the fan when t…

If your temperature gauge still operates when the ignition is switched off, as it does on some cars, you will see the needle rises after the engine has stopped. That is because it is measuring coolant temperature, not engine temperature. The engine is still much hotter than the coolant. Yes, the …

SteveF has it right…With all engine and cooling system designs, when you shut off the engine, you also shut off the water pump. Coolant trapped in the heads can boil as it absorbs the heat in the metal engine parts with no way of transporting this heat to the radiator. Running the fan for a few min…

That makes a lot of sense! Thanks for clearing that one up for me. One more little thing —now that you mentioned it—, the temp gauge always measures coolant temperature, or it depends on the car? The next time I’m driving I’ll make the experiment of checking the needle after I turn off the engine. …

percolation? The fan stops cooling the radiator and the water pump quits pumping water. Yes. The first thing an engine does when you shut it off is get hotter

When you turn off the car…the METAL the engine block is made of is still very hot. Hotter then the coolant that’s trying to cool it. So for a while after you turn it off the metal will be applying heat to the coolant…thus increasing the temp of the coolant. This is NOT good…especially on a hot summ…

“The next time I’m driving I’ll make the experiment of checking the needle after I turn off the engine.” Once you turn off the ignition of a modern car, the gauges return to their “zero” mark–or at least this is what happens on all modern cars with which I am familiar. However, if you want to retu…

Yep, that was just what I did. It indeed went past the middle (where it stays during normal operation). So I verified a new thing I’ve learned… Thanks a bunch!

Cooling fan running with engine off?

Maintenance/Repairs

pleasedodgevan2 July 11, 2011, 5:20am 10

The engine isn’t the only thing that gets hot. The fan helps keep the wiring and electronic junk from holding the maximum amount of heat. It can’t hurt to have the fan run for a while unless you have an old battery, but that’s easy to fix.

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Cooling fan running with engine off?

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