R.E.D Posted May 22, 2019 Share Posted May 22, 2019 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 Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/ Share on other sites More sharing options...
fjh Posted May 23, 2019 Share Posted May 23, 2019 (edited) Replace the tensioner also be sure your Ac unit is not giving you greif could be causing issues Edited May 23, 2019 by fjh Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423420 Share on other sites More sharing options...
R.E.D Posted May 23, 2019 Author Share Posted May 23, 2019 Will do.a/c is running good.. Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423422 Share on other sites More sharing options...
R.E.D Posted May 23, 2019 Author Share Posted May 23, 2019 Replaced both tensioners and belts .drove truck 10 miles and the thin belt is already starting to shred.nothin seems to be rubbing Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423526 Share on other sites More sharing options...
Rob Posted May 23, 2019 Share Posted May 23, 2019 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. Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423529 Share on other sites More sharing options...
JoeH Posted May 23, 2019 Share Posted May 23, 2019 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... Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423535 Share on other sites More sharing options...
R.E.D Posted May 23, 2019 Author Share Posted May 23, 2019 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 . Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423539 Share on other sites More sharing options...
R.E.D Posted May 23, 2019 Author Share Posted May 23, 2019 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. Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423541 Share on other sites More sharing options...
JoeH Posted May 23, 2019 Share Posted May 23, 2019 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. Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423542 Share on other sites More sharing options...
R.E.D Posted May 23, 2019 Author Share Posted May 23, 2019 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 Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423543 Share on other sites More sharing options...
JoeH Posted May 23, 2019 Share Posted May 23, 2019 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. Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423544 Share on other sites More sharing options...
R.E.D Posted May 23, 2019 Author Share Posted May 23, 2019 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 Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423545 Share on other sites More sharing options...
JoeH Posted May 23, 2019 Share Posted May 23, 2019 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. Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423547 Share on other sites More sharing options...
R.E.D Posted May 24, 2019 Author Share Posted May 24, 2019 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 Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423551 Share on other sites More sharing options...
R.E.D Posted May 24, 2019 Author Share Posted May 24, 2019 Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423555 Share on other sites More sharing options...
R.E.D Posted May 24, 2019 Author Share Posted May 24, 2019 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) Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423556 Share on other sites More sharing options...
steeler Posted May 24, 2019 Share Posted May 24, 2019 Maybe a stupid question, but is your plastic idler pulley still there? I've seen them go bad and break off the engine completely. Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423576 Share on other sites More sharing options...
R.E.D Posted May 24, 2019 Author Share Posted May 24, 2019 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. Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423580 Share on other sites More sharing options...
JoeH Posted May 24, 2019 Share Posted May 24, 2019 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. Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423584 Share on other sites More sharing options...
R.E.D Posted May 24, 2019 Author Share Posted May 24, 2019 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 Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423589 Share on other sites More sharing options...
R.E.D Posted May 24, 2019 Author Share Posted May 24, 2019 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 Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423590 Share on other sites More sharing options...
JoeH Posted May 24, 2019 Share Posted May 24, 2019 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. Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423593 Share on other sites More sharing options...
R.E.D Posted May 24, 2019 Author Share Posted May 24, 2019 It's separate.its the big pulley right below the ac compressor Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423595 Share on other sites More sharing options...
fjh Posted May 24, 2019 Share Posted May 24, 2019 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! Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423606 Share on other sites More sharing options...
R.E.D Posted May 24, 2019 Author Share Posted May 24, 2019 No noise at all.i have shook fan hub with belts removed and didn't notice anything .but will double check Quote Link to comment https://www.bigmacktrucks.com/topic/57331-mack-cv-serpentine-belt/#findComment-423613 Share on other sites More sharing options...
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