IQ 1.0 AUT making really bad noise - hard to diagnose please help

[Arai]

Hello everyone!

So I've got a 2010 IQ 1.0 Automatic with a CVT box.

Unfortunately my little car has intermittently started making a really awful noise and I had it to the mechanics today to get a diagnose.

Unfortunately again, they could not find anything wrong with the car, and when I took it for a spin with the mechanic of course it didn't make any of the bad noise then.

However, I recorded the sound a couple of days ago and hopefully someone of you can hear what it might be. When the mechanic heard the recorded sound he said it might be the gearbox, but when putting it in neutral it still makes the noise so my thought is that it cant be it. I thought that it might be the water pump but the mechanic said not a chance...since its not leaking.

The car usually starts getting noisy when I've been driving on the highway for approximately 20 - 30 miles. You cant usually hear it very well when driving on the highway but when I slow down it gets really present, and especially when opening the windows and the sound echos against the walls of the houses that I drive by.

It's hard to get a really good recording of the noise as it stops more or less 5-10 seconds after coming to a stand still but please listen to the attached sound file and see if you have any ideas at all. Thanks! 

badnoise.m4a

[nielshm]

What I hear is some kind of a rattle? If it was the gearbox, I would expect it to be more consistent, more metallic grinding or whining. Does the gearbox act normal or have acceleration /top speed changed? 

[Arai]

Gearbox is acting normal and acceleration is fine. Everything seems normal aside from this bad noise, there is a slight grinding noise as well that the recording doesnt pick up. The mechanic couldnt hear the grinding noise either but I can hear it slightly.

[nielshm]

Can you get some one else to drive the car, then you can stand outside and try to locate the noise, with the car driving by. Sitting in the cabin can make it much more harder to locate. 

[Arai]

Actually I've tried this as well. It's coming from the engine area but unfortunately the noise always stops 5-10 seconds after the car comes to a stand still and before you get a chance to open up the hood and have a closer inspection and pinpoint where exactly the sound is coming from. To make it even worse the noise isnt always there, so you cant just take the car out for a spin like me and the mechanic did today, because today there was no sound, atleast not loud enough like on the recording.

[fordulike]

Just to rule out any A/C compressor noise, switch the A/C off completely and see if the noise is still there.