I've owned my Sierra for over 5 years and 145,000 miles. I do most my own maintenance and feel I'm pretty in tune with the truck. Lately I've noticed an abnormal noise coming from the engine bay. I'm not sure if it's due to cold weather or just happen to begin when cold weather started. I took this video immediately after a cold start in my garage. Temp was around 38°F so cool but not really that cold. From what I can tell the sounds appears to be coming from the very front of the engine around the accessory drive. It's a little more noticeable on the driver side compared to the passenger side. Belts are all original but the vacuum pump was replaced in March. Sounds doesn't appear to be coming from that anyways. I'm wondering if it might be the belt tensioner? Belts look good but might be about time to replace them anyways.
https://www.youtube.com/watch?v=7YigepzOKcw
https://www.youtube.com/watch?v=7YigepzOKcw
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