530d e60 2004 very faint siren type sound only at very low revs


bmw 530d SE
Hi all
I have recently noticed a very faint siren/whining type of sound but only on very low revs at extremely light acceleration and when the pedal is released the sound is in reverse just like a siren.
Its not the turbo. ... well I dont think it is because the turbo only boosts about 2.5k revs which when it does it has its own distinctive sound since I removed my silencer.
It only occurs at the lowest possible revs 1-1.5k.
The other thing I noticed it doesn't occur when the car is stationary but only when it is in motion.

Even then when the turbo does boost down, a second or two later the faint siren type of sound can be heard. Its as if I have 2 turbos... one for very low revs and one for higher revs as in the 535d.... only I dont.
No codes showing on inpa diagnostics
Drives beautifully even at 160k miles! !!
I would be very grateful for any suggestions
Last edited:
Greetings and a Warm Welcome to our TorqueCars Forum my Friend! :)

I am unable to help you with your question directly, but hopefully somebody can point you in the right direction for the knowledge that you seek!

Good luck buddy! :)
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