W210 serpentine belt
 

The serpentine belt on our 98 E320 shows some strange wear on flat side (see picture below)
The spots on the rubber are quite soft. Almost like chemically or heat degraded. There also seems to be some wear at the edges.
Belt is OE and was replaced about 7 years ago by dealer (46k miles since).
Tensioner is new type.

Anyone else seen anything like that?

https://www.dropbox.com/s/s2wghxwr7z...marks.jpg?dl=1

Graham, there is no picture to view.

There is a picture and it shows up fine on my laptop and on my phone. Must be a problem your end. It is a DRopbox link.

In any event, I got the problem sorted over on BW 210 forum

And the problem was?

I was able to scrape those marks off using a solvent and plastic scraper!

That wear mark that runs the length of the belt looks to me like the belt is too loose and is rubbing on something.

That flat area is not rubbing on anything (other than the fan and tensioner pulley surfaces). The marks along edges may be because that was where more contact was because of build up in middle of belt. But it is not really that bad.

After cleaning
https://www.dropbox.com/s/kruqdw05u7...aning.jpg?dl=1

Could it have been a parts sticker that was on the belt that got melted and dragged across the surface over a couple thousand miles?

Hard to say at this point. More likely oil from valve cover breather leak and/or fluid from underside of PS reservoir which belt runs very close to. Or perhaps greasy oil/dirt off front of engine found it's way onto the tensioner pulley and then got heated and solidified.

Will watch for these things when I put new belt on.

New belt does have a manufacturer's sticker. Not sure if it can easily be removed - kind of well adhered. Looks like they don't expect that side to be in contact.

Graham, as you are aware the outside of the belt contacts the belt tensioner pulley and the fan pulley. The identification information, shown in the picture, is stenciled on the belt. There is no reason to remove that information as it will not affect the performance of the belt. Your engine may need a thorough cleaning if grease and grime are getting on the accessory belt.

The sticker is a plastic strip that ends up being molded into the belt, it isn't coming off. Sometimes the plastic is slippery and will make a chirp as the back goes over a flat pulley. I usually use some 80 grit sand paper to slightly roughen up the surface in an x pattern. Just enough to put a few scratches in the sticker but you can still easily read it.

The original belts were imprinted, but the aftermarket Bando that I now have has a separate shiny sticker. It won't peel off when new. Hopefully not in service! roughening it a bit might be useful, but I doubt it it is a real problem.

The original problem is oil getting on the belt, collecting dirt then the flat idlers ironing out the mixture.

Graham, a CRP-Contitech serpentine belt presents no service problems. Better to buy a premium quality belt than have issues with a lesser quality aftermarket brand.

You might check out this review:

https://toolstastico.com/best-serpentine-belts/

Bando top of list and mine was Made in USA! Been around for about 100 years! Also OEM supplier for many makes. https://www.bandousa.com/

I would have no problem using Continental - In fact that is what my full length spare is. Looks like they have more than one quality grade.

I have now bypassed the A/C compressor, so needed a 2310/2315 belt and the ones readily available here were Bando. Glad to see they are rated top of the heap and that their OE and aftermarket are same quality. :)

By the way, I had an OE MB (likely Conti) belt break on the W210 at about 100k miles. The idler and tensioner were replaced (with new design) at 47k miles, but looking at invoice, dealer didn't change the belt when they did that.

I would advise anyone with W210 or any other car to change the serpentine belt early. Don't wait for it to break!

I know from personal experience that it creates a dangerous situation. Ours broke on an elevated high speed expressway, with no room to pull off. You lose Power steering, Power brakes, Alternator and Water pump. Engine temperature skyrockets and engine/rad could be ruined. I was able to limp to exit by using the heater/blower with windows wide open to keep temperature down.