My 2003 Tribute has started squeaking. Seems to come from the main belt on the left side of the engine. Faint at idle, but gets somewhat louder as the rpms go up. Advice appreciated. What is the accepted protocol for dealing with this? How do I understand if the belt needs replacing, or if something is out of alignment? BTW, as best as I can see/feel it, the belt itself is in OK shape.

 

this should help:

 

Nice video. Thanks. That's a big help.