Loud fan noise when car first starts

[mikeyg07]

Everyone! I'm new here after recently purchasing my first Z4. I'm hoping you can help me find out whether something my car does is normal or not!

I've noticed that sometimes when I start my Zed, there's a loud noise than sounds like a fan which goes on for around 10 seconds. It's louder when I open my door. My air con is off. I don't hear a noise this loud at any other time.

Here's a video of it. https://youtu.be/xc8T-b3FmLY

It's a 2007, 2.0 engine.

Any thoughts? Thanks in advance!

 

[Jfgoldfish]

That is the secondary air pump. Completely normal.

It will run for up to 90 seconds at cold startup (when the engine is below 40 odd degrees Celsius).
Its purpose is to blow air into the exhaust manifold upstream of the catalytic converters in order to burn excess fuel at startup. The combustion helps heat up the cats and O2 sensors so the ECU can enter closed loop faster than without the system in place, thereby reducing emissions.

 

[colb]

https://www.realoem.com/bmw/enUS/showparts?id=BT33-USA-06-2005-E85-BMW-Z4_25i&diagId=11_3419
This is fitted as said in previous post to lower the emmissions when cold starting, it runs a short time then switches off automaticaly.
If you are in the USA then you need it to pass inspections, here in the UK it can be deleted and a blanking plate fitted to the cylinder head in place of the round silver coloured valve. Removal will not affect emmissions at MOT test time. If you delete it just tape up the electrical connector and tuck it away. You could make the blanking plate and a gasket to go with it, needs sealing off so you don't create an air leak that will upset your fuel trims.

 

[Jfgoldfish]

Be aware that deleting the SAP can cause a fault code to be logged due to the DME not detecting a rise in oxygen at the O2 sensors during startup.

I am sure there are ways around that though.

 

[mikeyg07]

Thanks for the replies - appreciate the help! It didn't happen the first couple of times I used the car (or test drove it) so was worried something may have gone wrong.