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What is the reason my honda civic 2005 (manual) hybrid turns the fan on, after I turn the engine off?

A mechanic told me that is meant to cool the engine down.

Why does Honda need to have the engine assisted in cooling down? Why not just let it cool down by itself? What is the point?

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1 Answer 1

up vote 5 down vote accepted

Because the coolant stops circulating when the engine is turned off, the engine actually keeps getting hotter for a while after the engine has been turned off. If the engine gets hot enough (above 112 degrees Celsius/ 230 Fahrenheit) the aluminium cylinder head can start warping, causing uneven pressure on your head gasket, causing it to blow the next time you turn on your engine. As far as I am aware, the engine block itself also contains aluminium, so keeping it cool is even more important than engines with cast iron blocks.

The fan coming on when you turn off your car is meant to keep the temperature beneath the safe threshold. Maybe your car's engine was designed to run hotter because it improves emissions figures. For instance, my car was designed to perform optimally (emissions-wise) at 99 degrees Celsius, which is just below the boiling point of water. Obviously that's a bit dangerous and therefore the fan also turns on after a drive on a particularly hot day.

If this is really annoying to you, I suggest you find out from an auto-spares shop if there are cooler-running thermostats that you can have installed that will open sooner and keep your engine cooler, possibly negating the need for the fan to be turned on when you turn the ignition off.

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Why then is it found only in my Honda, which has a diminutive 1.3L engine? Why? Aren't other cars, with larger and newer engines also of Al content cooling their engines down? I mean, in the parking lot just outside the doors of the office, my car is the odd one out. People would be walking pass my car and hearing this fan sound from a motionless car like as though the engine is still on. –  Cynthia Avishegnath Jun 20 at 8:32
    
I've updated my answer. –  Juann Strauss Jun 20 at 8:43
    
@BlessedGeek ... So even after Jaunn gave you a valid and correct answer, you are still wondering why? This seems it is your issue and not the vehicles. This is just the way Honda designed the car. It is a good thing and not a bad thing. Also, Honda is not the only car which does this. Many cars do this, especially turbo cars. Just because it annoys you doesn't mean there is anything wrong with the car. If it is that bad, trade the car in on something else. Me? I'd just stick with the Honda and call it a day. –  Paulster2 Jun 20 at 11:15
    
In his defense, I add the second half ("Maybe...") after he added the comment. –  Juann Strauss Jun 20 at 11:23
    
... she/her ... –  Cynthia Avishegnath Jun 23 at 9:33

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