[FormulaMMM]

Originally Posted by THE TECH

Interesting. Never heard that noise before.

Surprised me as well! In an oh shit... kind of way.

Originally Posted by Krozi

It's just a little vanos rattle when the top of the engine doesn't have a lot of oil cause it's been sitting. I get it every now and then when I haven't driven for a while.

Originally Posted by quackman

Yeah, I've been having that sound on and off for years now I think. Happens when I don't drive the car for a couple days, and is more noticeable when it's been even longer.

Originally Posted by motortrend

I think I got that once, sounds pretty bad in person. The car had been sitting for about a week so that might be it. Only happened once though

Thanks for sharing fellas. Good to know, I think, that it's not necessarily a unique issue. Definitely time dependent -- when I'm daily driving I don't hear it. After the car sits for a time then it reappears, which does perhaps lend some credibility to the idea that it's an oil/lubrication issue. As in components get a bit dried out.

Originally Posted by RussRamz

It's normal. It's the activation sound of the secondary air pump (SAC). It's strictly an emission system and is designed to activate based on engine temperature. The longer it sits, the longer this pump will operate during warm-up.

I'm becoming a bit more convinced on the normalcy of the issue, but it really does not sound like air pump activation of any kind.

Originally Posted by M3PO

This is WRONG. The sound that the OP is worried about is an issue with the VANOS, not the air pump or normal VANOS sounds. I had this exact sound (I posted in the thread the OP linked) and BMW replaced one of my VANOS units and the sound is absolutely gone.

Thanks for the thoughts. I saw your posts in the related thread and wondered if the VANOS replacement permanently resolved the issue. So should I expect the issue to get progressively worse over time? Something that could lead to other problems?