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High-pitched buzz/whine when engine is stopped

28318 Views 72 Replies 34 Participants Last post by  CuoreAlfa
Hi all,

I'm a fairly new owner of a '62 plate 170 TCT diesel.

I've noticed that when I turn the engine off, there's a high-pitched whining/buzzing noise coming from the engine bay somewhere. It doesn't matter if the engine's been run for a few moments or a half-hour or more. Is this normal? Has anyone else noticed it, and if so does anyone have any idea what it may be?

Just curious...

Thanks in advance,
Biggsy
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Holding vacuum for a day, I doubt that is a manufacturer goal and I'm not sure that is a design requirement by any car producer? I think you will find here are two distinct differences between petrol and diesel engines. Petrol engines by their very design create vacuum in the induction manifold, diesel engines usually have to rely on a cam shaft driven vacuum pump to create vacuum for the brake system servo and other bits and bobs. The production of vacuum needs to be fairly instantaneous or how would your brakes work straight after pulling out of the airport car park after a 2 week holiday?
 

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i think you'll find turbo engines don't necessarily have vacuum in the manifold, and modern engines like the MA don't necessarily have a throttle valve anymore. I don't have an MA so can't check (could check on Eper if you insist) but a lot of petrols have vacuum pumps these days.

I also work as anf have worked for several years asq a mechanic, and I tell you the Brake servo circuit needs to hold vacuum for a long time, we've had recalls for this in the past (peugeot that was)
 

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only ever seen 1 vehicle with an electric waterpump, and that was a jag xj without turbo.
It's not the main water pump, that will be mechanical. It's an auxiliary pump, probably dual function. 1 to assist with circulation through the heater core 2 to run on a timer after the engine is switched off to prevent hot spots as I describe in previous post. I know Jag's have them (I've replaced the one on my G Wagen when it failed with a Jag one and saved myself a bag of cash, same Bosch part number) , plus VW, Merc. Audi, Seat............. I don't know if Alfa's have them, just a suggestion. When they are running it's extremely difficult to tell as they are so quite but if it was failing that could be the noise.
 

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did anyone come to a suitable reason why this happens? or what it is? i think mine started doing this today, i high pitched electrical sound, ill upload a video if anyone can help me out, and who has more knowledge than me,
 

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I get this high pitched noise too? And it just started to happen
Starts as soon as doors are open and keys out of ignition after a drive, it stops for a second or so when locking the car but then continues.

Has anyone found a fix?
 

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whatever it is doesnt seem to be a problem, infact seems to be normal, nothing is broken so no fix required, the noise hasnt got any worse on my car and still runs runs well i guess theres nothing to worry about, still would be nice to know what exactly it is, and i cant believe no one does know, the mystery continues.
 

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Just heard this on mine tonight for first time after owning for over a year. It seems to change in volume when something electrical is used, goes quieter when doors are unlocked but then loud when locked again. Waited a couple of minutes and it was still going.

Seems to be coming from back of engine bay, am I right in thinking the box fixed to the back is the ecu, certain it's that which is buzzing.

Did anyone ever come to an answer as to what this is?

Sent from my F3111 using Tapatalk
 

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I think its electrical because the noise follows the dimming of the interior lights - as if its feedback through the electrical system as the capacitor discharges. When I had my GT it did this too - and it was much louder when I had an amp fitted to the sound system.
 

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Mines only happens when the theatre lighting powers up & powers down & the sound comes from the speakers.
 
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