what is that sound?

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Tue 14 Dec 2004 09:44
what is that sound? - barney100
When I turn off the engine on my merc w reg 220 diesel there is a whirring sound that lasts for about a minute then dissapears. It isn't the cooling fan and my usual fonts of knowledge are as baffled as me: any ideas?
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Tue 14 Dec 2004 09:53
what is that sound? - Schnitzel
Auxilary waterpump?
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Tue 14 Dec 2004 10:22
what is that sound? - Zenta
My old Vectra had an air pump to help the cat get up to temperature, sounded like a hairdryer for the first minute or so.
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Tue 14 Dec 2004 10:38
what is that sound? - Truckosaurus
Another suggestion: certain high end vehicles have some sort of 'magic' heat retaining device so the cabin heater is warm from the first moment you start the car, perhaps you car has one of these and the noise is it being 'recharged'.
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Tue 14 Dec 2004 10:42
what is that sound? - volvoman
I get the same noise on my Mazda MPV and when it cuts out afer about 30 secs. you can hear the cooling fan quietly whirring away.
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Tue 14 Dec 2004 13:40
what is that sound? - adverse camber
On the A4 tdi there is a noise after switch off which is some sort of pressure valve releasing - apparently it is bad news for the turbo if it doesnt make that noise.
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Tue 14 Dec 2004 22:41
what is that sound? - Colin M
It is a coolant pump continuing for the benefit of the turbo.

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Wed 15 Dec 2004 09:16
what is that sound? - volvoman
I know I didn't ask the original question but thanks for the answer - the noise was starting to bug me.
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Thu 16 Dec 2004 22:52
what is that sound? - Pete M
I had a Honda Accord once, that used to make a particularly rude burping noise about a minute after shutdown. It turns out it was a valve that was part of the petrol tank vapour recovery system.
Quite a mystery until it was tracked down. No cure apart from changing the valve, so we lived with it.
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