Hello ,

There are 2 distinct lines on my serpentine belt, is this an indication that the tensioner / idler pulley is going bad?

 

I think it's a sign your belt is rubbing on something. Have a careful look around and see if you can figure out what it's touching.

If that all checks out, take a look at all of the flat-faced pulleys and see if you can find anything unusual.

 

What's the mileage on the car? The M272 is well known to chew up tensioners and pulleys. I'd just throw in a new set if you haven't done it in a while. I think OEM might be INA or Gates. You can either get a whole kit or get the parts individually. Did one car about 7 years ago and they're still holding up. The INA kit from Rockauto is about $120, a little less after using a 5% discount code you can find on retailmenot.com, but only has a one year warranty. Or you can get a kit from FCPEuro for $150 and that would also have a lifetime warranty. Or you could try and figure out if it's the pulleys or tensioner but I think it's just easier to replace them all at once instead of just doing one and then doing another a little while later.

https://www.rockauto.com/en/moreinfo...11659&jsn=1079

https://www.fcpeuro.com/products/mer...-272273beltkt1

 

looks to me like idler pulley above AC is out of alignment, what indicate bad bearing.
Remove the belt and move all pulleys, feeling for bad bearing

 

+1. If you look at the inside of the tensioner wheel, there is clearly a faded area that has formed. It's time.

 

OP: Your tensioner is going bad. This just happened to my ML350, the belt looked just like yours.

 

See attachments.

 

thank you konigstiger