[SomeRandomer123]

HELP! My car has tinnitus!!
My engine is making a really loud whistling sound even though it is off and the key is out!
The car hasn't been running for over 3 hours so the engine is now cool enough to touch but still slightly warm. I was washing it and noticed a whistling noise. I put my ear to the bonnet and concluded it was coming from the car, so I opened it up and sure enough, the sound was coming from the bottom right section of the engine where the video below shows.
Sorry the video isn't the best of quality, I used my Android Phone to take it. The whistling was intermittent. At one point (most of the time on this occasion) it was very loud and high pitched, but then it would go away all together for a few seconds then come back quieter and gradually louder to the volume and pitch the video shows.






What is making the sound and why? Have you had any experiences like this? Is it a problem?

Your help would me much appreciated!
2009 E90 BMW 330d 60k miles.

EDIT: Car is now at 80k miles and I haven't caught it whistling again so I'm not concerned, just very curious!

[TERAKO35]

My car makes that same noise. It was doing it today.

[SomeRandomer123]

Really? A 28i? Hmm. I can't stress enough how loud, high pitched and long the whistle was. Was it that bad on yours? I'm no expert but I'm pretty sure an engine shouldn't whistle - especially when off!

[TERAKO35]

Originally Posted by SomeRandomer123

Really? A 28i? Hmm. I can't stress enough how loud, high pitched and long the whistle was. Was it that bad on yours? I'm no expert but I'm pretty sure an engine shouldn't whistle - especially when off!

It sounds just like that - maybe not as loud. It can last up to 5 mins. I will try and record it next time I get the chance. I had an 06 E90 that never made that sound but my new Coupe has done it since day one. I have had it for a few months now.

[SomeRandomer123]

Interesting... Well, the 'd is going in for a service in the next few weeks so will ask them then.

[Railgun]

Water pump not shutting off or cycling? If it`s been off for more than three hours, that`s the only thing I can think of.

[SomeRandomer123]

The whistle is so loud, it would be heard whilst driving so I doubt it...

[kaleb]

That's almost certainly an electric motor driving a fan or propeller, so I'm gonna go ahead and say it's your water pump, but I don't know if your car has that feature like the N54 does.

[SomeRandomer123]

3 hours after running when the engine is luke warm? Is it a fault? What feature are you regarding on the N54?

[kaleb]

Originally Posted by SomeRandomer123

3 hours after running when the engine is luke warm? Is it a fault? What feature are you regarding on the N54?

On the N54, when engine oil temperatures are at a certain threshold, the electric water pump will continue to run while the engine is off. This keeps coolant circulating through the turbos so that the very hot turbos won't "coke" the oil and clog the oil passages. It's the reason why "turbo timers" were invented.

The sound on my car is similar to what your video sounds like, but not exactly the same but I could attribute that to real life versus electronic audio sounds.

The electric pump on the N54 doesn't run for hours after I turn the car off, however, only minutes at most. This would lead me to believe you have some kind of fault as discussed in earlier replies.

Either way it is very curious.

[SomeRandomer123]

Curious indeed! Like I mentioned earlier, If the water pump made that noise when the car was running, it would be audible and lead me to believe a fault was present. I understand that the turbo(s) need to cool but 3 hours after use?! Haha either way, I'm not overly concerned about it - just extremely curious. Next time I catch it doing it, I will put a little soapy water around some pipe connections to see if it bubbles and therefore identify a possible air leak.

[SomeRandomer123]

I should add that I have had the bonnet open with engine running and engine hot and have never heard the really loud whistle. I am certain it would be audible even with the engine on. I doubt this has any link to it but you never know - it had a problem with the glow plug control unit so they were not coming on to pre-heat on cold starts and were coming on (to overheat) whilst driving. A new one was fitted and all is back to normal. I have never heard a car whistle whilst off so something must be on. I hope the battery isn't being discharged!

[SomeRandomer123]

Originally Posted by kaleb

On the N54, when engine oil temperatures are at a certain threshold, the electric water pump will continue to run while the engine is off. This keeps coolant circulating through the turbos so that the very hot turbos won't "coke" the oil and clog the oil passages. It's the reason why "turbo timers" were invented.

The sound on my car is similar to what your video sounds like, but not exactly the same but I could attribute that to real life versus electronic audio sounds.

The electric pump on the N54 doesn't run for hours after I turn the car off, however, only minutes at most. This would lead me to believe you have some kind of fault as discussed in earlier replies.

Either way it is very curious.

Now I've gathered much more knowledge since I posted this, I can tell you that my N57 does have the feature where the water pump will continue to run to cool the turbo, but even after driving the car hard, it is inaudible. After 80k miles, it hasn't returned but some guys have commented on my YouTube video's (one with an E46) saying he is having the same "problem".
Very interesting.... I don't expect to find the answer really. Oh well