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2001 ML320, 2000 ML430
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Discussion Starter #1
My serpentine belt shredded on my 00 ML430 yesterday. Started smelling burning rubber and then the battery light came on. I replaced the belt, tensioner, and idler pulley about 35,000 miles ago so I am surprised at the failure. On the tensioner pulley there is a buildup of rubber indicating to me that the belt seized. There also is a small chip in the edge of the vibration damper which may have occurred when the belt shredded.

My questions are this: 1) will the buildup of rubber cause problems that would require replacing the tensioner pulley?, and 2) is the chip in the edge of the vibration damper something that would require immediate replacement? I have a photo that shows both areas. Thanks for any guidance.
 

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Dallas, Texas
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My serpentine belt shredded on my 00 ML430 yesterday. Started smelling burning rubber and then the battery light came on. I replaced the belt, tensioner, and idler pulley about 35,000 miles ago so I am surprised at the failure. On the tensioner pulley there is a buildup of rubber indicating to me that the belt seized. There also is a small chip in the edge of the vibration damper which may have occurred when the belt shredded.

My questions are this: 1) will the buildup of rubber cause problems that would require replacing the tensioner pulley?, and 2) is the chip in the edge of the vibration damper something that would require immediate replacement? I have a photo that shows both areas. Thanks for any guidance.
Show us the belt. Or whatever is left.
 

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1999 ML320, 1998 SL500
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1,149 Posts
As an innocent and un-informed observer I would have to think that the tensioner pully seized. Otherwise, why the buildup of rubber on it?

It may rotate now but I would think it is what stopped the belt.
 

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1999 ML320, 1998 SL500
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No idea how accurately them vibration damper is balanced but if it were my car I would wrap the new belt around that area and see if the belt could be cut by the edges of the broken place and how much the belt relies on the edge there.. If it looks safe I would probably ignore it.

There is a tiny chance that the break is related to the failure, cause or effect. Can you say that it is a new break by looking at the surface?

I still favor my first notion so far.
 

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2001 ML320, 2000 ML430
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Discussion Starter #9
Do not recall ever seeing this break before. I was thinking that the free strand may have whacked it while flying around. Just don’t know if a compromise in the structure of that damper - no matter the size - is cause for immediate replacement.
 

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My serpentine belt shredded on my 00 ML430 yesterday. Started smelling burning rubber and then the battery light came on. I replaced the belt, tensioner, and idler pulley about 35,000 miles ago so I am surprised at the failure. On the tensioner pulley there is a buildup of rubber indicating to me that the belt seized. There also is a small chip in the edge of the vibration damper which may have occurred when the belt shredded.

My questions are this: 1) will the buildup of rubber cause problems that would require replacing the tensioner pulley?, and 2) is the chip in the edge of the vibration damper something that would require immediate replacement? I have a photo that shows both areas. Thanks for any guidance.
something is seizing somewhere , clean as best as you can , put new belt and watch .belt dont seize , something cause it to self destruct .not worry about chip .a/c ok , alternator ? water pump .usually when a bearing fail , there is a noise before total failure .
 

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Very viable theory.
You may need to look through your notes. Tensioner with steel riveted pulley has not been offered for sale in at least 10 years.


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ML320 W163 2000 189 7 seater
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Haha, you've jinxed my car! I read this post yesterday and thought 'bad luck', and now my serpentine belt has just exploded! I had checked it last week as there was a slight squeak from it, but the belt looked okay. The idler/tensioner pulley that runs against the back of the belt had seized but loosened easily enough, and the belt had wrapped around the fan clutch, but came off easily enough. Thankfully, it hadn't gone five miles later as I would have been off road near Hawes in the Yorkshire Dales and the AA would not have been amused... Oh well, it is a nice sunny day to be waiting in my car for them to come. I hope the send a truck first and not a van but they say they will be here in half an hour so they must have been nearby anyway.
 

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ML320 W163 2000 189 7 seater
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Haha, you've jinxed my car! I read this post yesterday and thought 'bad luck', and now my serpentine belt has just exploded! I had checked it last week as there was a slight squeak from it, but the belt looked okay. The idler/tensioner pulley that runs against the back of the belt had seized but loosened easily enough, and the belt had wrapped around the fan clutch, but came off easily enough. Thankfully, it hadn't gone five miles later as I would have been off road near Hawes in the Yorkshire Dales and the AA would not have been amused... Oh well, it is a nice sunny day to be waiting in my car for them to come. I hope the send a truck first and not a van but they say they will be here in half an hour so they must have been nearby anyway.
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2001 ML320, 2000 ML430
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280 Posts
Discussion Starter #14
Haha, you've jinxed my car! I read this post yesterday and thought 'bad luck', and now my serpentine belt has just exploded! I had checked it last week as there was a slight squeak from it, but the belt looked okay. The idler/tensioner pulley that runs against the back of the belt had seized but loosened easily enough, and the belt had wrapped around the fan clutch, but came off easily enough. Thankfully, it hadn't gone five miles later as I would have been off road near Hawes in the Yorkshire Dales and the AA would not have been amused... Oh well, it is a nice sunny day to be waiting in my car for them to come. I hope the send a truck first and not a van but they say they will be here in half an hour so they must have been nearby anyway.
Things happen in threes, I hear, so we should have some company here soon.
 

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2001 ML320, 2000 ML430
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280 Posts
Discussion Starter #15
So, Witek, is your guess that it is the tensioner? It only has about 35,000 miles in it but I guess they can fail anytime.
 

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1999 C230 Kompressor
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36 Posts
My serpentine belt shredded on my 00 ML430 yesterday. Started smelling burning rubber and then the battery light came on. I replaced the belt, tensioner, and idler pulley about 35,000 miles ago so I am surprised at the failure. On the tensioner pulley there is a buildup of rubber indicating to me that the belt seized. There also is a small chip in the edge of the vibration damper which may have occurred when the belt shredded.

My questions are this: 1) will the buildup of rubber cause problems that would require replacing the tensioner pulley?, and 2) is the chip in the edge of the vibration damper something that would require immediate replacement? I have a photo that shows both areas. Thanks for any guidance.
 

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1999 C230 Kompressor
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36 Posts
Make sure all pulleys are in alignment. Check vibration damper, does it wobble? Does the A/C
Work?
 

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Dallas, Texas
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So, Witek, is your guess that it is the tensioner? It only has about 35,000 miles in it but I guess they can fail anytime.
Tensioner for sure as the one you have now is old design that was prone to failure. Alternator pulley does not look very good. There are shiny spots in the bottom of grooves. That means belt sinks in too deep and peaks of pulley slice belt lengthwise into fettucine.
 

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1999 ML320, 1998 SL500
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1,149 Posts
I guess I'll have to have a look at our cars. I never thought much about how the belt fits the grooved pulleys.

Anyhow it looks like the pully in the picture is shiny on the peaks which could cause the belt to be shredded if that is the main load point.
 
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