Belt shredding?

[JHZR2]

My 2008 MB ML320 has a slight oil seep from the front. It’s one of the intake gaskets, and is fairly common.

I know the serpentine belt, which is 8-row and one of the larger ones I’ve seen, is about due to but with the oil seepage, I’m not replacing it yet.

To help with that checkout, I had started to do some other things. One was to clean and re-seal some of the other air intake pieces.

So this air intake silencer item in the bottom/left was pristine, say, 600 miles ago:

Note the black shavings just beneath the belt?

They’re soft and rubbery. Not sure why. Everything spins, runs, turns, etc. as it should. I don’t see these bits anyplace else under the hood.

The belt moves fine, it doesn’t resonate, wobble, shake or anything else. Engine is as smooth as glass.

I don’t suspect any pullies or consumers on the engine.

Could this be due to a soft tensioner spring? If not that, what?

 

[Jetronic]

Make sure the belt is still properly seated on each ribbed pulley. And then check for bolts unthreading.

 

[eljefino]

Do we know for sure the age of the belt? Maybe it's new and breaking in. (It doesn't look old.) Maybe the car was sitting a while and the pulleys corroded but wiped themselves clean, shredding your belt in the process. If it were mine I'd clean and monitor, which you seem to be doing.

 

[Gyro Gearloose]

Check for any loose bolts, worn bearings, or anything that could result in a misaligned pulley, especially the ones near the crumbs. My power steering pump came loose and shredded a new belt in about 100 miles. By contrast I have an untouched belt with over 150K that still looks new.

 

[JHZR2]

Make sure the belt is still properly seated on each ribbed pulley. And then check for bolts unthreading.

Everything appeared to check out ok. Some versions of this engine have a 7-rib belt, I wonder if one of the pullies could be the wrong one?

Do we know for sure the age of the belt? Maybe it's new and breaking in. (It doesn't look old.) Maybe the car was sitting a while and the pulleys corroded but wiped themselves clean, shredding your belt in the process. If it were mine I'd clean and monitor, which you seem to be doing.

It’s probably in the receipts. Doesn’t look that old, or new…

What I know is that kind of mess was there, I cleaned it all, now a few hundred miles later it’s back. I’ve never seen a belt shed such material.

Well, once… my 96 Ram with original tensioner. When I bought it, there was some residue… after I swapped an OE tensioner, it went away. Makes me wonder if the belt may be too slack??

 

[JHZR2]

Found a photo from late April when I was cleaning up the mess. It’s on the tensioner too. Seems to be all over.

 

[Gyro Gearloose]

The ribs on the idler on the bottom right appear different from the one on the left. The outside ribs look lower and rounder in the photo and it has no guide edge. Is that the way it is supposed to be?

 

[IndyIan]

The ribs on the idler on the bottom right appear different from the one on the left. The outside ribs look lower and rounder in the photo and it has no guide edge. Is that the way it is supposed to be?

That's what it looks like to me too. Have the ribbed profiles on belts/pulleys been standardized across all manufacturers for a long time? I wonder if a pulley has a slightly different profile?

With that much stuff flying off of it, maybe run it in the dark with a bright flashlight and see if you can see the dust flying off in one spot?
Or run it at high-ish rpms for a few moments when everything is cold and the feel the pulleys for which one is warmer? Or which part of the belt is hot?

 

[spasm3]

Could it be there from a previous owners issue? Like a wrong belt, or incorrectly routed belt by the previous owner ?

 

[JHZR2]

The ribs on the idler on the bottom right appear different from the one on the left. The outside ribs look lower and rounder in the photo and it has no guide edge. Is that the way it is supposed to be?

I believe the lower right is a smooth pulley, so that’s the belt riding on the pulley on its back.

The one on the left is the 8-rib crank pulley. IIRC.

Could it be there from a previous owners issue? Like a wrong belt, or incorrectly routed belt by the previous owner ?

Absolutely. I havent changed belts yet. I know it’s due, I’ve driven it a few thousand miles, I wanted to deal with a bit of oil on the front of the engine (believe it’s a PCV seal actually), and the belt wear issue.

 

[Trav]

Have you counted all the ribs on all the pulleys? That is lot of material being thrown off.

 

[spasm3]

Absolutely. I havent changed belts yet. I know it’s due, I’ve driven it a few thousand miles, I wanted to deal with a bit of oil on the front of the engine (believe it’s a PCV seal actually), and the belt wear issue.

I meant an issue thats already resolved.

 

[JHZR2]

Have you counted all the ribs on all the pulleys? That is lot of material being thrown off.

I need to pull the belt off entirely. They switched from 8–rib to 7-rib belts not long after my engine #, so it’s entirely possible.

Belt looks ok though. Which is why I have to wonder if the tensioner is just weak and causing wobble in the belt in some cases. There is hardly any space between the belt and other stuff for some of its run.

 

[JHZR2]

I meant an issue thats already resolved.

Couldn’t have been resolved, because I cleaned everything up and in 500 miles it came back.

 

[Egg_Head]

Not saying this will fix your issue, but MB's seem to really like MB branded belts. That is one of the few OE parts I insist on buying for my cars.

 

[PontiacHO]

Oil leak causing crude build up that’s getting onto a pulley. Pressure washer time.

 

[JHZR2]

Oil leak causing crude build up that’s getting onto a pulley. Pressure washer time.

But how does that crud shred the belt?

Or scuff the belt? Since the belt is consistent and in good shape, no chunks, cracks, etc.

 

[JHZR2]

Not saying this will fix your issue, but MB's seem to really like MB branded belts. That is one of the few OE parts I insist on buying for my cars.

Contitech is generally the MB manufacturer.

 

[GSCJR]

I have to wonder if the tensioner is just weak

This is my guess.

Double check that the belt route and length are also correct.

 

[PontiacHO]

But how does that crud shred the belt?

Or scuff the belt? Since the belt is consistent and in good shape, no chunks, cracks, etc.

Then don’t ask for opinions if you’re going to argue them! How’s that?