Odd sound.. help?

[LukeHawk]

Hey guys. So I was driving home from work the other day and I noticed a weird sound coming from my car (320i N20 engine).

I can only describe it as a faint dull whistle. It occurred on a humid/rainy-ish day.. and only at low revs/coasting. disappeared when driving at faster speeds and immediately disappears when the engine stops (observed with the auto-stop/start at a robot). The intensity of the sound does not change with revs or anything like that.. Actually very hard to hear unless you're used to the cars normal sounds. Its not from the air-con either, as with this off the sound was still present. It COULD have been some sort of air escaping somewhere? But again.. goes away when the engine is off. Seems to come from the front somewhere.

It happened twice on that day only, and I have not heard it since... but I'm wondering if anybody else has experienced this and if its any cause for alarm? Just a freak occurrence and nothing to worry about?

 

[Jeremy.d]

I can only imagine that its an air leak. Maybe try the engine cleaner test to try and find it.

Hope you get sorted bud:thumbs:

 

[LukeHawk]

I can only imagine that its an air leak. Maybe try the engine cleaner test to try and find it.

Hope you get sorted bud:thumbs:

Never heard of that, I'll check it out thanks! I drove around a bunch today again and the sound never came. I'm starting to think a bit of rain water got in somewhere and worked itself out or something.. but still unusual.

 

[LukeHawk]

Update to my issue!

So its been happening on and off this whole week. I noticed that turning off auto stop/start completely gets rid of the issue. Slowing down before a stop would usually cause the whistle. But with auto start OFF it doesnt happen. I can even cut off the whistle buy turning off auto start when it happens. Interesting...