Hey there guys, I recently picked up a 2011 G37 6MT with 139,000 miles a month ago, and it has this high pitched ringing noise that I can't seem to find. It goes away sometimes but come back. Anyone have any ideas of where I could start, or what the problem could be? Thanks in advanced!!! I posted a video below:

 

Does the squeal change with engine RPM? If I were to guess I'd say one of the belt idler pulley's are starting to fail. That squeal is a bearing screaming for grease.

I'd remove the belt and spin by hand each of the idler pulley's. They should spin smooth as silk. And resistance, roughness, or excessive "wobble" indicates the bearing is likely shot and the unit needs to be replaced.

Again, that's my take on that sound.

 

I think you are probably right. Car is currently pretty high mileage, and so I will try to get the belt + pulley kit in the next 2 weeks to replace it all. Hopefully it'll fix the issue. In the meantime, you think it's safe for me to drive for a few weeks?

 

Rule #1. Do no throw parts at a problem without fully diagnosing same. At the very least, remove the belt and spin each pulley by hand as suggested above. Alternatively, you can carefully spray a few touches of WD-40 or equiv. spray lube being careful to prevent overspray onto the pulley shaft. It will not be easy but if even a few drops make it to the bearings the squeal should abate.

That said, at ≈140k miles it probably is time for those components- tensioner, idlers, and belt- to be replaced. You should be fine driving the car until you source the parts though I would not venture far from home. However, if the squeal gets louder or presents at highway speeds then I would park the car. If the issue is a pulley and one of them seizes, the belt might snap which can cause other issues. At least these idlers are metal- my BMW uses plastic idlers

Good luck and please keep us updated.