E89 N20 Engine - Rattle Noise when Cold on Low RPM

[TomZ4]

Now with temperatures dropping down when I cold start my car I get a rattle noise around 800-1700 RPM when engaging the gear and accelerator gently on gears 1-3. It sounds like it's coming from the central air vent area, people hint me towards either timing chain, disa valve, heat shield and/or vanos bolts. I spoke with BMW service and they don't have any recalls for this model. Advice welcome.

Below is link to audio:
Skip to 1:15 - Starting on 1st gear from standstill
1:35 Right turn from low speed
2:10 - 2:25 - short starts with 1st gear slight engagement and slight acceleration
3:05 - acceleration and change to 3rd

https://drive.google.com/file/d/16oxrGc ... sp=sharing

No other noise issues at idle or with engine heated up.

Cheers

[Smartbear]

Now with temperatures dropping down when I cold start my car I get a rattle noise around 800-1700 RPM when engaging the gear and accelerator gently on gears 1-3. It sounds like it's coming from the central air vent area, people hint me towards either timing chain, disa valve, heat shield and/or vanos bolts. I spoke with BMW service and they don't have any recalls for this model. Advice welcome.

Below is link to audio:
Skip to 1:15 - Starting on 1st gear from standstill
1:35 Right turn from low speed
2:10 - 2:25 - short starts with 1st gear slight engagement and slight acceleration
3:05 - acceleration and change to 3rd

https://drive.google.com/file/d/16oxrGc ... sp=sharing

No other noise issues at idle or with engine heated up.

Cheers

That doesn’t sound like a cam chain noise to me, if it’s coming from the central air vent area I’d guess it’s got something to do with the ventilation fan & not the engine.
Have you tried driving the car with the fan turned completely off?
Rob

[TomZ4]

Yeah, this was recorded with aircon off and phone on that vent.

[Pbondar]

Yeah, this was recorded with aircon off and phone on that vent.

Aircon off is not the same as fan off

I agree with Rob..doesn’t sound like a cam chain..there is no DISA on N20s..

Possibly the vacuum pump which sits at the back of the engine and driven off the camshaft..but again sounds more like a metallic spring caught in a fan..

[TomZ4]

Took it to a RAC garage under warranty and the guy checked for heat shields and anything obvious. Couldn't locate the issue.

The suspicion now is DMF Booked an Indy BMW for march for them to have a look

[TomZ4]

Bingo!

Thanks for help. Took out the AC fan out and the rattle noise is now gone.

The fan at the driver seat is not seized and looks perfectly fine so I will replace it, just to make sure there isn't any other fans/bits in AC system that are driven directly by air pressure?

https://ibb.co/Dk3T2Jj