What's causing these lines on my serpentine belt?

[AdsoYo]

My belt has what looks like lines of dirt on the flat side for a few months now. The car is a Saab 9-7x 5.3i with a Magnuson supercharger. There's no squealing or slipping, the pulleys look clean and straight, and the belt is straight and centered on each pulley. The tensioner has accumulated a lot of dust and I'm not sure if that's from the plastic pulley or the belt. I just want to make sure the belt isn't disintegrating. It's a Gates Micro-V 6PK2765.




You can see the lines can be wiped away.

 

[Mooseman]

The only pulley we don't really see is the water pump. How does it look? Might have some wear marks on it. How's the tensioner? Not too tight? Is it the proper belt? Does the tensioner still have some play?

 

[movietvet]

Yea, the lines get on there because of whatever is on the pulley's and the pulley's conditions. You can remove belt(s) and clean it all, belts and pulleys and check for good tension on the tensioner. I am in Oregon, too. Where in Oregon are you? Desert area?

 

[AdsoYo]

The only pulley we don't really see is the water pump. How does it look? Might have some wear marks on it. How's the tensioner? Not too tight? Is it the proper belt? Does the tensioner still have some play?

This is the best shot I could get of the water pump. I replaced it when I did the cam in October/November.

Tensioner is original. I'm not sure how tight is "too tight" but it does feel tighter than any other vehicle I've worked on. I do see it move/adjust while the engine is running.

The belt came with the supercharger kit.

Yea, the lines get on there because of whatever is on the pulley's and the pulley's conditions. You can remove belt(s) and clean it all, belts and pulleys and check for good tension on the tensioner. I am in Oregon, too. Where in Oregon are you? Desert area?

I'm in Bend. The car never sees dirt or mud. None of the pulleys are noisy. The only one that is even slightly suspect I would say is the tensioner since it has that dust layer on it but it contacts the ribbed side of the belt. The belts on my other vehicles don't look like this. Aside from these lines the belt looks fine: no cracks and it's not unraveling on the edges.

Cool to see another Oregonian in here, small world!

 

[Mooseman]

The tensioner shouldn't be overly tight or near the end of its travel. There are usually marks on it between the two halves that show where it should be. Found this thread on LS1 that talks about it and has some examples of the marks and where they should be.

Tensioner Indicator - LS1TECH - Camaro and Firebird Forum Discussion

Conversions & Swaps - Tensioner Indicator - I believe my belt has stretched and it may be too loose, but I'm not completely sure how to read the gauge. There are definitely 3 lines there, but there may be a 4th as well, it's hard to tell. I'm not sure where the proper area for the notches to...

ls1tech.com

This image I found is the type I usually see.

If it's outside the tension limits, you might have the wrong belt length.