Buzzing sound from motor on startup / above idle

[gavsadler]

Hello all,

I refer to my thread elsewhere re: our X3 35i.

When starting the car, there is a horrible buzzing sound / metallic noise coming from the top of the motor somewhere. It buzzes for a few seconds and then goes quiet. Then if you break the idle (to about 1000rpm), the sound starts again and remains until you either drop back to idle, or rev above 1000rpm.

It almost sounds like some sort of solenoid adjusting something - could it be the Vanos unit(s)?

I have a sound clip on my phone which I can share if required. I wanted to check if anyone knows what this could be or if their cars do the same?

Thanks

 

[BillyBob]

If you can definitely pin-point the origin as being the top of the motor, a Vanos solenoid is a likely culprit... But it's a very rare/unlikely point of failure.

My money's rattling wastegates though - it's a noise that reverberates throughout the engine bay.

 

[gavsadler]

I'll try do some more listening this weekend when there is more time.

Thanks for the heads-up on the wastegate rattle. I'll see if I can pinpoint the issue, perhaps using a hosepipe to listen carefully.

The reason I thought it could also be the vanos unit is because I see on the motorplan history that the vanos solenoid was replaced at 70000kms

 

[akash]

Is the car still on MP.

If it is take it straight to BMW.

However there is a way to test if it is the waste gates via the vacuum canisters.

I think there is a clip of the test on Youtube.

 

[Serg_ZA]

Could potentially be an exhaust heat shield that's rattling at certain RPM. The exhaust manifold heat shield on my M54 rattles so I need to nip up my bolts in order to stop that.

 

[gavsadler]

Here's a link to 2 video clips I recorded of the noise.

Clip1

Clip2

 

[akash]

That does not sound like the waste gates

Im basing this on my experience with my N54