What is your question?
The problem occurs only after the car has sat overnight or for at least 3 hours. It doesn't make the sound every time. Sometimes it doesn't make it for a few days, sometimes it makes the sound twice a day (if 3+ hours have passed since last turning it on). My car has always had regular oil changes. I have had the following things replaced but the noise still happens: Timing chain, starter (Sept, 2018), new battery (6/2019), Ignition coil assembly, spark plugs, AND tightened loose belt (8/6/2020) - the next day it made the noise again. It hasn't gotten better or worse. It is as if it is acting on its own unrelated to anything. I am concerned that something is being worn down or damaged that can't be detected (or won't be until it breaks). Anyone want to chime in? It started in Sept. 2017 and no one has been able to figure it out cuz it won't make the noise while they have the "stethoscope" ready. Naturally. Thank you!
What makes this problem better or worse?
I gave you all the info.
How long has your 2009 Pontiac Vibe had this problem?
Since 9/2017
I see you stated “tightened loose belts” - that is NOT possible - - the belt tensioner is self contained and provides tension adjustment automatically - no manual adjustment is provided. There is only one belt.