I noticed a constant squeak sound coming from under my hood, so I checked it out, and my belt tensioner has rattling back and forth. Is this normal? Or is this something I can just tighten down, or do I need to replace it? The movement from the belt is causing the tensioner to rattle back and forth. Or could it be something totally unrelated to the tensioner?

It looks exactly like this:

 

it will move with belt but if it squeaking then it needs replaced. and replace belt when you do it

 

it only rattles and squeaks when it's idling. When the engine accelerates, the squeak and the movement in the tensioner stop.

 

it is just starting to go than, but remember you only have one belt so when it does go and you overheat or run your batt. low and it wont start you seen the signs. preventive maint. goes a long way

 

Thanks for the help hall. I went to the store and picked up a new tensioner and put it on. No more rattle or noise.