Can anyone advise what this sound might be that's coming from my engine?
https://youtu.be/ek6iIYliHNg
Many thanks
Ash
https://youtu.be/ek6iIYliHNg
Many thanks
Ash
Strange sound from engine...
- Thread starter mofofunk
- Start date
Eh? the turbo has no choice but to be turning if the engine is running and pushing exhaust gases past its drive (turbine) wheel !
Cooling fans would be a cheaper answer, but I'd hope that as he is investigating this "strange sound from engine" he would have made sure that the AC was switched off, so that would mean if the noise was engine coolant cooling fan, and it was running with the engine on with hot coolant, then it would continue to run as the engine would be still hot when the engine was switched off?
Also, there was no demonstration of any noises being present with ignition on and engine off, it only seemed to start when engine started?
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There's a bit info in the video description on your tube.
It's not the fans that I am certain off because I can see they are stationary.
The air con stopped working about 2 month ago and this noise seemed to appear not too long after so I can assume it might be related. Not knowing a great deal about air-conditioning/pumps etc I was loth to tie it down to that.
The noise starts when I start the car, normally lasts for about 60 seconds, stops for about 5 mins, comes back on for about 10 seconds then stops. I then wont hear it again until the car has been switched off and I go to restart it after a few hours.
If I switch the car off and restart within about an hour or so the noise doesn't occur again.
If i switch the engine off within the first seconds of the noise (like on the video) you can hear the noise 'running down'.... This is the reason I did that on the video so the noise could be heard more clearly
RUM4MO....picking up on your point at the end of your post, there are no noises when the ignition is on but the engine isn't and also the air con is off
It's not the fans that I am certain off because I can see they are stationary.
The air con stopped working about 2 month ago and this noise seemed to appear not too long after so I can assume it might be related. Not knowing a great deal about air-conditioning/pumps etc I was loth to tie it down to that.
The noise starts when I start the car, normally lasts for about 60 seconds, stops for about 5 mins, comes back on for about 10 seconds then stops. I then wont hear it again until the car has been switched off and I go to restart it after a few hours.
If I switch the car off and restart within about an hour or so the noise doesn't occur again.
If i switch the engine off within the first seconds of the noise (like on the video) you can hear the noise 'running down'.... This is the reason I did that on the video so the noise could be heard more clearly
RUM4MO....picking up on your point at the end of your post, there are no noises when the ignition is on but the engine isn't and also the air con is off
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One other thing, does that engine in that car have a "run on" electric water pump, though I'd doubt if that was making these noises that it would spin on for so long after engine stop. To me, the only thing that gets spun up and has enough weight to take that time to run down after engine has stopped moved is still the turbo assembly.
Edit:- if it was the AC compressor it would stop as soon as the engine did, even if it was noisy or its coupling had sheared.
Another Edit:- if you think that it might be the turbo, you need to get that seen to quickly before I starts to break up and cause real damage. But safe than sorry etc.
Edit:- if it was the AC compressor it would stop as soon as the engine did, even if it was noisy or its coupling had sheared.
Another Edit:- if you think that it might be the turbo, you need to get that seen to quickly before I starts to break up and cause real damage. But safe than sorry etc.
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i think you need to do some reading up about how turbos work.
to me it sounds like an electric motor/compressor, possibly the bearings have run dry, perhaps a belt has failed...
can you not do a more thorough check to get the location of the sound? certainly sounds like its from the front end and not the rear end
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Okay, I don't mind being wrong, but explain how you think a turbo works. The drive wheel is in the exhaust manifold, any exhaust gases passing out through that manifold are going to turn the drive wheel and cause the compressor side to spin, even at low engine revs - unless the shaft bearings are seizing a bit. How the compressor side charge air is controlled is another issue, what I was suggesting was that there is very little in an engine and its support parts that would have enough energy to run on once the engine had stopped rotating, other than the turbo. But as I said, come back with your explanation of how a turbo works and I'll see where I have gone wrong, every day can be a school day!
Edit:- my issue with the AC compressor theory is that it has a direct, or belt drive, when the engine stops rotating it will and this noise goes on for a lot longer than that, same thing for belts. The air pump idea does sound like an alternative source of this noise now that I see that there is one fitted to these cars.
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I'm still waiting for andycupra to get back with how a turbo works that would mean it is not spinning at engine idle!
I'm very keen to learn where I went wrong.
I'm very keen to learn where I went wrong.
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ok i should have been clearer in my comments. the turbo may spin at idle, but wont boost or spin at any noteable rate as its not underload. in my opinion it would not be able to be spinning at such a rate that it would continue to run on like this.
I've never experienced or heard a turbo spin after shutoff like this.
for me id get a more accurate acount of where the sounds is coming from in the engine bay, difficult via the video, but it seems to be at the front of the engine bay?
Remember that the AC compressor on these cars is permanently coupled, when not asked for, it runs at maybe 5% normal displacement, the effective displacement is only increased by an internal swash plate on demand. The issue for me wrt the AC was "is it OFF or is it ON" only from the point of view that if it was ON the fan(s) would be running, and it might be a possible source of that noise - but the OP has cleared that up, it was OFF.
PS, "swatch" is definitely not the name for that type of device, but it sounds a bit like that! It is in reality just a "wobble" plate with a variable throw.
Edit:- I've corrected the name of that type of plate, it is swash plate, see Sanden Variable Displacement Compressors for further details if interested.
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Well as you are the second person to suggest that, and I did not know these engines in Europe used these things, I'd reckon that you are correct, or it would be a lot easier for the OP if you are!
They were listed for my old Passat 2.8 V6 but never fitted to European market cars - I spent a long time searching for it after hearing them mentioned on a US of A VW forum.
This makes me think secondary air system too, it's the only thing that runs for the first 60 secs, then stops and briefly starts again. If it was related to the turbo,A/C, alternator etc etc then the noise would be there all the time.
Never heard a secondary air pump make that noise before, but my money would be that the fan blades inside the pump are rubbing against the inside of the housing.
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