I have 160k miles on my 03 leSabre. How can I test the belt tensioner to see if it needs replacement because the spring is not pulling as hard on the belt?

Is there a way to test?

I need to replace the heater bypass tubes and could replace tension while it'* off if it'* needed.

Usually the belts stretch a tad which makes it seem like the tension isn't as good as it use to be. I've seen my tensioner sit at a different angle after I install a new belt.

I have a 4.3l, my tensioner has 3 marks on it... if you are between the last 2 you should be good. I just changed my serpentine belt at 142,000

look at the belt tensioner and see if the 2 marks line up. easiest way to tell