[KingMichaelR]

I was just driving back home on the highway and I randomly heard this annoying rattle/knocking sound coming from the front of dash/windshield just randomly come and it has not gone away.

Car:
2009 335i xDrive N54 engine

- Seems to only happen when I'm going 60-80km/h
- car does not lose power (FBO and stage 2 tuned)
- car steering does not shake
- not vibration in seats/car

It sounds like its coming from the front vents/dash but I've checked everything I could find online

- checked the top vents to make sure screws weren't loose
- checked the fenders to make sure they were bolted
- checked sway bar
- checked cabin filter for pieces
- checked engine cover and intake system
- changed wiper blades

I cannot figure this our right now, its SO annoying, it sounds like something in stuck in the vent of behind the dash and just rattling when the wind hits it at those speeds, it will knock around progressively getting louder and then just stop.

I attached a video of what is sounds like you can find it here:

if ANYONE had a similar issue PLEASE let me know, ima go insane with this.

[lowrydr310]

I had a piece of broken plastic lodged in my blower motor, causing a vibration in the dash and an occasional rattle.

I also had a really annoying dash rattle which ended up being a loose strut brace bolt. At the center of the dash under the hood where the strut braces bolt to the firewall, I forgot to tighten it completely.

[KingMichaelR]

Originally Posted by lowrydr310

I had a piece of broken plastic lodged in my blower motor, causing a vibration in the dash and an occasional rattle.

I also had a really annoying dash rattle which ended up being a loose strut brace bolt. At the center of the dash under the hood where the strut braces bolt to the firewall, I forgot to tighten it completely.

Was the vibration also happening when the blowers were off?

I'll check the strut braces tomorrow and see if that was hitting anything.

It def seems like something wind related.

[Joanthanthaniga]

I had a similar noise before. i spend lot of time on forums and things.
Later when i try to adjust the steering wheel, the rattle gone away. It was like my brother locked the steering so low, touching the dash and cause noise

[lowrydr310]

Originally Posted by KingMichaelR

I was just driving back home on the highway and I randomly heard this annoying rattle/knocking sound coming from the front of dash/windshield just randomly come and it has not gone away.

Car:
2009 335i xDrive N54 engine

- Seems to only happen when I'm going 60-80km/h
- car does not lose power (FBO and stage 2 tuned)
- car steering does not shake
- not vibration in seats/car

It sounds like its coming from the front vents/dash but I've checked everything I could find online

- checked the top vents to make sure screws weren't loose
- checked the fenders to make sure they were bolted
- checked sway bar
- checked cabin filter for pieces
- checked engine cover and intake system
- changed wiper blades

I cannot figure this our right now, its SO annoying, it sounds like something in stuck in the vent of behind the dash and just rattling when the wind hits it at those speeds, it will knock around progressively getting louder and then just stop.

I attached a video of what is sounds like you can find it here:

if ANYONE had a similar issue PLEASE let me know, ima go insane with this.

I just watched the video and WOAH that's loud... It might still be the blower motor but the blower is behind the glove box. Is that where the sound is coming from? It's easy to remove - I won't try to explain it but there are several posts here with instructions. When I had the broken plastic in my blower motor it was off balance and made a similar sound, but not as loud as yours.

It might also be an issue with one of the mixer flaps. Maybe there's a broken flap or a problem with one of the motor shafts. Does it change if you move the airflow between the top, middle, or lower vents, or toggle the air recirculation flap?

[KingMichaelR]

Originally Posted by lowrydr310

I just watched the video and WOAH that's loud... It might still be the blower motor but the blower is behind the glove box. Is that where the sound is coming from? It's easy to remove - I won't try to explain it but there are several posts here with instructions. When I had the broken plastic in my blower motor it was off balance and made a similar sound, but not as loud as yours.

It might also be an issue with one of the mixer flaps. Maybe there's a broken flap or a problem with one of the motor shafts. Does it change if you move the airflow between the top, middle, or lower vents, or toggle the air recirculation flap?

It sounds like its coming from the centre-driver side more, it comes on for a bit when accelerating then stops at like 70-80km and then I wont hear it again for the rest of the drive, its so weird but driving me crazy

[Mike K]

Strut braces at the center bolt possibly? Worth a shot tightening it. An e18 on my car.