Whining sound when Turning off engine

[Dedespo]

I've noticed a high pitched whining sound when turning off the engine which starts high-pitched and pitch lowers as time goes by, sound fades away within ~ 3 seconds.

Cams? The whine only appears when switching off, never heard it in motion or revving.

Belts changed 5k miles ago.

 

[Jimmy]

If it only happens when switching the engine off, could it be the fan??

 

[Dedespo]

No mate, its not the fan. In any case, the fan would not turn-off when turning off the engine, it's the other way around usually.

My sound disappears within 3 seconds of turning off the engine. It's a discreet sound so i guess when idling its masked by other engine sounds and once i turn-off it's the only sound left and therefore noticeable until it winds down.

 

[Chris]

Id be inclined to say fan belt, they make a whine sometimes.

 

[Dedespo]

Maybe you can enlighten me but i would think that if the radiator fan is on when you have reached your destination and park, it would stay on for a bit more after turning the engine off and not turn-off simultaneously unless its a coincidence which in my case it's not, it's every time.

 

[Chris]

Depends how hot the engine is.

 

[Dedespo]

Of course it depends on engine temp and that's what i'm saying, if the car is hot enough for the fan to work while its underway and breathing air, it sure would be hot enough for the fan to keep working when it comes to a hault and therefore not turn off when you turn off the engine. Unless it's engine driven which i highly doubt. So my sound must not be fan-related.

 

[Jimmy]

Of course it depends on engine temp and that's what i'm saying, if the car is hot enough for the fan to work while its underway and breathing air, it sure would be hot enough for the fan to keep working when it comes to a hault and therefore not turn off when you turn off the engine. Unless it's engine driven which i highly doubt. So my sound must not be fan-related.

I'm no mechanic so it was a bit of a guess with it possibly being the fan to be honest. If the engine is hot after a drive and you come to a standstill, my (limited) understanding is - because the engine is no longer getting any cooling from moving air, the fan kicks in to draw in air whilst idling?

If you then switch the engine off, I assume that the fan would also wind down (possibly the whine you've experienced). The engine wouldn't necessarily require the cooling from the fan as it's no longer operating?

I might be wrong, so if anyone with better knowledge than I have puts me right, fair enough

 

[Chris]

I'm no mechanic so it was a bit of a guess with it possibly being the fan to be honest. If the engine is hot after a drive and you come to a standstill, my (limited) understanding is - because the engine is no longer getting any cooling from moving air, the fan kicks in to draw in air whilst idling?

If you then switch the engine off, I assume that the fan would also wind down (possibly the whine you've experienced). The engine wouldn't necessarily require the cooling from the fan as it's no longer operating?

I might be wrong, so if anyone with better knowledge than I have puts me right, fair enough

You pretty much just typed out an identical post to what I wanted too

 

[Jimmy]

You pretty much just typed out an identical post to what I wanted too

great minds and all that! We still might be totally wrong about what's causing the whine though!!

 

[Foxspeed]

just pull the fuse for the fan and see if the noise disappears...

 

[Chris]

great minds and all that! We still might be totally wrong about what's causing the whine though!!

Atleast the Clio genius foxspeed hasn't completely dismissed our thoughts haha

 

[Foxspeed]

iirc when you switch the engine off it kills the cooling fan...but it would still run down (ie make a noise) when the ignition switched off if it was running say for the air-con condenser or cooling the engine

 

[Craig211]

It's the fan, I had this same query a while back so after a drive I got home left car switched on then got someone else to switch it off whilst looking in the engine bay and as soon as the engine stops the fan winds down, I think it's because when you open the door auxilary power is killed i.e lights radio wipers etc

 

[Dedespo]

I see what you mean now, but the sound doesn't just get quieter , it disappears altogether. Fan sound is very distinctive anyway and i am sure it's not that. Sorry for over-analyzing :bash:

 

[Foxspeed]

I see what you mean now, but the sound doesn't just get quieter , it disappears altogether. Fan sound is very distinctive anyway and i am sure it's not that. Sorry for over-analyzing :bash:

as said you need someone else to switch it off while you find the cause of the noise

 

[Dedespo]

Update:

This high pitched noise can now be heard not only when turning off the engine (in which case it wound down and stopped as if something working in a spinning manner was turning off) but also in random maneuvering or generally slow speed stop & go (short whines). I am starting to think it might be some pump which is working under strain. What pumps do we have that might be making this sound? Or any other thoughts on what else it might be?

 

[Chris]

Are you using the air-conditioning?

 

[Dedespo]

No, air-conditioning always off.

 

[Dedespo]

Update:

Still haven't gone to my mechanic to look this up because he was out of town with a racing team.

I tried to locate the source of the sound this morning while having someone else turning it off. I'm pretty sure its coming from the left side as i look from the front so there is a possibility of it coming from the belts. (as per previous owner, belts have been changed 6k km ago). I took a video, will upload once i'm home this afternoon. In the start of the video you can hear the same sound randomly giving out a small squeek and then when i power off you can hear the full orchestra.