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Discussion Starter #1
I notice there is a whirring noise from the engine bay of my 2.0 petrol Mazda 3 for about 30 secs after the engine is turned off. What is this? It sounds like a pump running perhaps to pressurise the fuel line?
 

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Discussion Starter #3
Probably your electric radiator fans? Do you live in a hot area?
The fan is not running. The sound is from the vicinity of the engine block and you also hear it if you turn the ignition on/off without starting the engine.
 

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Gremlins? :grin2:

Dono, but am sure someone here will be able to tell you. If it isn't the radiator fans, I can't think of anything else that should be making a noise like that and would "make it for about 30 seconds after the engine is turned off"... that's what the fans do when the engine is hot. Maybe you can record the sound and post it here?
 

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Gearhead
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Many new cars have this sound after they are turned off (again not related to hot tempearture nor consequent fan running).
 

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Rubber side down
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I hear the noise as well from my 2.5 manual. It sounds like some sort of cooling fan to me, but it isn't the radiator fans. Are there any electrical components that have cooling fans blowing over a heat sink anywhere in there?
 

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Discussion Starter #14 (Edited)
I enclose a recording of the sound I hear from turning off the ignition or engine until the noise stops when you hear a relay click. The duration is about 40s. This recording was done just turning the ignition on/off with a cold engine so it's nothing to do with cooling fans. The noise is a bit louder than you normally hear since I left my phone on the cylinder head cover to make the recording. I had to be creative to embed a .wav file in a .doc file then compress that in a .zip file to meet the forum file upload requirements!

I expect this noise is entirely normal but what is it?
 

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I have a 2015 Mazda 3 2.0 hatchback. I have a noise like you are describing coming from my engine after I shut it off as well. (I have not listened to the recording yet, but from the description it seems like the same.) I just concluded that it was normal, because it is consistently doing it, and I have had no trouble with the car so far. I have about 40k miles on it.

I think it is normal and nothing to worry about. But nice to know to satisfy curiosity.
 

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Hoon Apprentice
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It is a normal sound. People ask about it all time.

Mine sounds like it is probably a fuel pump or the power steering motor doing something.
 

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I enclose a recording of the sound I hear from turning off the ignition or engine until the noise stops when you hear a relay click. The duration is about 40s. This recording was done just turning the ignition on/off with a cold engine so it's nothing to do with cooling fans. The noise is a bit louder than you normally hear since I left my phone on the cylinder head cover to make the recording. I had to be creative to embed a .wav file in a .doc file then compress that in a .zip file to meet the forum file upload requirements!

I expect this noise is entirely normal but what is it?
Hmm.. that didn't work for me.. All I get is a doc with the name of the wave file. Can you just add the wave file to a zip and upload it or give a link to it?
 

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OK, that one came though. Very strange; sounds very high pitched somewhat like an electronic sound.. this is really turning into a mystery.. I'm going to go down and see if I hear it in my car.
 
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