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R.E.D

Mack cv serpentine belt

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Hello fellas.i have changed belts twice today on the truck.they keep popping off.seems to me like the thin belt is the one with the issue but once it goes it takes The other one with it.everything seems to be aligned as far as pulleys goes except for the tensioner that is bit off center.could this cause it to pop off? bearing on all pulleys seem to be in good shape.please advice .

Thanks 

RED

 

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Posted (edited)

Replace the tensioner also be sure your Ac unit is not giving you greif could be causing issues 

Edited by fjh

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Will do.a/c is running good..

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Replaced both tensioners and belts .drove truck 10 miles and the thin belt is already starting to shred.nothin seems to be rubbing

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13 minutes ago, R.E.D said:

Replaced both tensioners and belts .drove truck 10 miles and the thin belt is already starting to shred.nothin seems to be rubbing

Is any ancillary drive, (a/c compressor, alternator) etc. running smooth or vibrating during operation? Make certain the clutch is locked in and turning the a/c compressor when the system is running. When the belts are off are the sheaves, (pulleys) rotating smooth and easily by finger pressure?

If everything is in alignment I would suspect the front bearing in the a/c compressor clutch first unless certain the compressor is running constant.

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Post pictures of tensioner etc. My 12v Cummins dodge belt likes to rub on the arm of the tensioner because the AC compressor pulley is some cheap China knock off. Jumps one rib on the AC pulley then it's happy, after it eats one rib off the belt though...

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When I replaced the tensioner on top ,the dowel that holds it from rotating was sheared off.i thought this was the problem.but just after a few miles with the new components the belt shredded one of the grooves .

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Not sure if it's worth mentioning , but it seems like this started happening since the fan is kicking on more often due to high temps in texas.i bought the truck in October of last year and this is it's first southern summer.

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No it should be able to run anywhere. Something isn't right  on it. Check engine damper wheel run-out. Maybe the crankshaft is bent.

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I thought of that but the small belt isn't connected to the crankshaft.it uses power from the fan pulley.and the small belt is the one that rips first then it takes the other with it once it wraps itself around it

 

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To clarify, as I'm not real familiar with CV's, the thin belt is to the air conditioner from the fan? Separate from the serpentine belt? 

Take the  belt off the AC for a day (driver will hate me) and see if the serpentine belt holds up. AC is a creature comforts, not mandatory. Engine water pump and fan spinning are mandatory.

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4 minutes ago, JoeH said:

To clarify, as I'm not real familiar with CV's, the thin belt is to the air conditioner from the fan? Separate from the serpentine belt? 

Take the  belt off the AC for a day (driver will hate me) and see if the serpentine belt holds up. AC is a creature comforts, not mandatory. Engine water pump and fan spinning are mandatory.

The cv uses two belts.wide belt only goes from crankshaft to fan pulley and is has it's own tensioner.the thin belt runs the water pump , alternator , ac compressor and it goes thru an idler pulley and it's driven by the fan pulley .so just undoing the ac would render the belt two long 

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Understood. That's a weird serpentine setup, I would have expected crank, water pump, alternator and tensioner to be together and the AC to be on it's own, driven by the fan/water pump. Are you buying belts from the dealer or cheap Napa belts? Napa is fine for cars etc but they're sh*t for trucks IMHO.

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 the first two sets of belts I bought since Monday were a combination of Pai brand and gates.today I bought original bulldog parts and same result.i just caught it earlier

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This how it looks like.the big belt is missing in this image.the belt shreds from the inside part (where arrow for number 4 is pointing)

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Maybe a stupid question, but is your plastic idler pulley still there? I've seen them go bad and break off the engine completely.

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5 hours ago, steeler said:

Maybe a stupid question, but is your plastic idler pulley still there? I've seen them go bad and break off the engine completely.

Yes it is .I hate to throw parts at a problem without properly diagnosing the issue but if I can't see anything rubbing against belt today , I'll be changing that plastic idler pulley in order to eliminate variables.

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Change it, run it for 15 seconds, and shut it off. See who the belt is slipping off of or rubbing against. I'll bet you'll find someone not aligned properly.

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Will do.i left the damaged belt on.two loads so far today and so far so good .I'm running with the windows down no ac and trying to stay off the skinny pedal in order to keep fan clutch from engaging

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Does anyone have the part number for the idler pulley?I can buy it with next day shipping at a quarter of the price from my local mack dealer.same brand .thanks 

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Is the water pump part of the fan pulley or is that the water pump between AC and Alternator? My Cummins dodge is set up with water pump separate from fan.

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It's separate.its the big pulley right below the ac compressor

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These used to have issues with fan hub bearings packing up on the AI engines  due to the extra heat  when the truck was first introduced! is it possible the hub bearings a toast! just throwing that out there! Also the crank  Damper is a possible as mentioned however never seen one fail out of the blue before! fan hub bearings make a whining noise when standing in front of the truck!

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No noise at all.i have shook fan hub with belts removed and didn't notice anything .but will double check

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