Throwing belts

i am not certain a fan clutch, as much as i'd think about the crank pulley (or harmonic balancer), since it is pressed into place surrounded by rubber to dampen the vibrations.

misalignment is an issue of maybe a device connected to the crank that was not installed correctly, or may be loose, or have a broken mounting bolt.

 

Look and see if the belt grooves are worn. If the belts are trying to roll when they are tightened that's most likely it.

 

Im going out on a limb and guessing this is a ddec 3, or early 4 engine, and harmonic balancer is original? Replace it, with a new 14 liter balancer. And has the kysor fan clutch been adjusted lately?

 

He's saying your pulleys are worn. When the new belt v does not match the worn pulley there is not enough contact area for the belt to bite, grip the pulley. Causing heat and the belt fails or rolls.

Also common with v belt pulleys is the belt will actually bottom out in the bottom of the pulley due to excess wear. Once it does no grip, just slip. New belts will fix it briefly then it's the same old story.

 

Damper, or harmonic balancers do wear out, Cummins recommends replacing every 500,000 miles. I would imagine Detroit has similar numbers. There is a viscous fluid in the damper, with age it hardens, then bad things happen. I’ve seen them actually blow apart, it can be an expensive repair.

 

Best to start replacing, I replaced all of mine, including damper at around the 800,000 mile mark. No more belt issues.

 

Maybe someone put the wrong belts on it at one time??

If there too wide they wont fit in the pulleys properly. They will sit too high.

I find it hard to believe if belts are the right ones and adjusted correctly that they would ever pop out. Worn pulleys will only make it slip but never pop off. My guess they are the wrong width belts