Just like the title says...

How do you know when your belt tensioner needs replaced? Is there a visual indicator (i.e., the #1 hole isn't completely visible when the belt is installed, etc...) or some kind of physical test?

I replaced my belt a few weeks ago and the #1 hole is slightly hidden versus being completely visible.

Thanks!

 

when the belt keeps comming off or squeel because there is insufficient tension.

 

I have a rattle in the engine bay. I took it to a local shop and its the belt tensioner. I will have the car back tomorrow hopefully. If you notice a noise or rattle when the car is in Reverse or Drive (auto) or when the engine has load on it, then check that area of the car. In my case, it was the tensioner. I have 102K on my 06 R53 with a 15% alta and the ATI 2%