W211 E280 CDI Poly V Belt Snapped

timtjohnson

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Had my W211 (2007) E280 CDI serviced yesterday which included replacing my worn Poly V (serpentine) belt. Within 20 miles of leaving the garage the red 'battery' symbol appeared on the console and the power steering also failed (wow! I did'nt realise just how heavy the steering really is - almost dangerous!). As I was only one mile from home I decided to continue driving. When I lifted the bonnet I was shocked to see a completly shredded belt!

The belt has damaged some of the smaller pullies and also melted itself onto some of them. The garage (local indy who are usually very good)has agreed to recover the vehicle and make good the damage first thing on Monday.

Three questions.

1. Any suggestions what would have caused a brand new genuine MB belt to fail?

2. How likely is this to have caused any other damage thats not immediately apparrant? Any thing I can inspect?

3. Could it happen again? I need to drive my young family 400 miles this coming weekend and don't fancy calling out the RAC late at night from the hard shoulder of the M4?
 

television

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If it was only replaced as it was worn,, it has to be the way that it was fitted I feel
 

Silver_Star

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A few possibilities are: incorrectly fitted belt or a pulley that was seized or had play in it. or the belt could have just been a faulty one.

Before a belt is fitted it would need a thorough inspection, but I shouldn't worry too much about it, sounds like your indy will put it right for you.
 

scotty2hotty81

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As silver star said it could have been a faulty pulley, it's not easy to fit a belt wrong.
 

Richard Elliot

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I've had the same thing, two broken belts - a pulley was seized which promptly ruined the new belt. Fortunately not too expensive a failure and easy to rectify.
 

drdel

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Always go for the obviously and the circumstance. For a new belt its usually overtightening will do it - assuming as others have said none of the pulleys are seized or partially seized. If a pully was stiff or partially seized it would have sounded like a pair of fighting of cats

If the car was running fine before its unlikely a pully would have seized within hours of being serviced. If no other parts need changing then I guess your Indy overtightened it.
 

Steve@Avantgarde

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Water pump failure normally throws the belt off too, incredibly unluck if it has happened but not the first time I have seen a water pump fail after a new belt has been fitted. The extra tension from a new belt exposes a weekness in the water pump and a failure will be soon and certain!!
 

star

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Always go for the obviously and the circumstance. For a new belt its usually overtightening will do it - assuming as others have said none of the pulleys are seized or partially seized. If a pully was stiff or partially seized it would have sounded like a pair of fighting of cats

If the car was running fine before its unlikely a pully would have seized within hours of being serviced. If no other parts need changing then I guess your Indy overtightened it.

You cannot overtighten the belt as it has an Automatic spring tensioner! With Steve on this, sometime things just happen, sods law that its just been serviced. I would think a idler pulley has siezed (the melted one).
 

toby1

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Water pump failure normally throws the belt off too, incredibly unluck if it has happened but not the first time I have seen a water pump fail after a new belt has been fitted. The extra tension from a new belt exposes a weekness in the water pump and a failure will be soon and certain!!

Happened on mine, although not a W211. New belt advised and pulleys fitted after a service.

Within a month the water pump failed on the M4! New belt and pulleys again!
 

drdel

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Star - Unless tensioner etc are fully released its certainly possible to over-stretch the belt during fitting and once the inner fibres have been fractured the life will be v. short
 

star

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Star - Unless tensioner etc are fully released its certainly possible to over-stretch the belt during fitting and once the inner fibres have been fractured the life will be v. short

You try and get a belt on without holding off the tension, when you remove the belt the tensioner goes to full travel, you then have to move it back to fit the belt. You might be thinking of the old type of tensioner.
 

drdel

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Star said "...when you remove the belt the tensioner goes to full travel, you then have to move it back to fit the belt..."

Exactly the point. If you think about what you wrote that's why if you take the short-cut method of using the new belt and 'winding' it over pulleys and allowing it to pull the tensioner back; unless its done with care it is possible to 'injure' the belt
 

Roxie

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If you look at the tensioner there is a hole in the housing and another in the lever. The idea is you pull the tensioner up and put a peg through both holes, this locks the tensioner in place. You then do whatever you want with the belt and only release the tensioner when the belt is back in place.

If you allow the spring to unwind in the tensioner it can and does jam up in the housing and break it. This is why a new tensioner comes already tensioned up.
 

star

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Star said "...when you remove the belt the tensioner goes to full travel, you then have to move it back to fit the belt..."

Exactly the point. If you think about what you wrote that's why if you take the short-cut method of using the new belt and 'winding' it over pulleys and allowing it to pull the tensioner back; unless its done with care it is possible to 'injure' the belt

But its no more tension applied to the belt. ( still not the correct way tho) The melted pulley is the give away.
 

star

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If you allow the spring to unwind in the tensioner it can and does jam up in the housing and break it. This is why a new tensioner comes already tensioned up.

Never had one jammed, the pin is to allow ease of fitting as one of the attaching bolts is obscured if the tensioner is released, so very difficult to fit.
 

Roxie

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The Pin has to be used to relieve the tension. Believe me they do break not always but I can tell you that a new one will snap as easily as an old one.
 

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timtjohnson

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Problem resolved.

Thank you to everyone for your comments and advice. My reliable Indy returned car today, they replaced a seized (and melted) idler pulley and put on another new belt. Not sure whether pulley seized before belt snapped or not but all sweet again.
 

star

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Thank you to everyone for your comments and advice. My reliable Indy returned car today, they replaced a seized (and melted) idler pulley and put on another new belt. Not sure whether pulley seized before belt snapped or not but all sweet again.

It had to sieze before the belt snapped, causing the belt to snap. (cant sieze after belt snapped, nothing is turning). Glad all is ok. :)
 

blackslide

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Our local parts dealer 'motonet' (nationwide in Finland) sells v-belts that most, look like they're cracked on the outside. They cost a lot and I wonder if they have been standing in the storage for too long and dried up? Well, I'll fit it and keep the receipt, if it fails I'll demand a brand new one + compensation, or a MB original belt. :/
 
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