2005 LaCrosse 3.8L Odd Idle Noise
 

Hello everyone! The video linked is a recording of the car at idle warmed up with a couple of revs.. Any idea what the sound is? Any help would be great! Thank you!

I couldn't tell very much from the recording, but if you want to pin it down, you might rotating the belt tensioner until you can get the belt off. Then rotate the water pump pulley, the alternator pulley, the idler pulley and last the pulley on the air conditioning compressor and I would be reasonably sure you will find the noise source sounds like a defective bearing.

Thanks for the suggestions! The whistling noise turned out to be the water pump.. started it for work one morning and hear a loud knocking, the bearings for the water pump were completely gone and the pulley was wobbling causing the knocking sound.. still made it too and from work... Water pump sized as I pulled into O'Riley's after work.. 10/10

If you are going to do the job, good practice , always replace the thermostat, the belt, the tensioner and coolant. Not a good feeling right after you do the pump , the thermostat sticks or the idler pulley on the belt tensioner gives out and you have to go back in there again. Do it right and do it once.