With some long trips, 6500 miles, coming up and all the posts regarding serpentine belts I think I should have a spare with me.I already keep tires less than 5 years, TMPS, Silverleaf for data, fluid changes and test regularly have roadside assistance in case of emergency, and keep extra filters with me but have no idea what size belt to get.Is it better to measure the one on the coach or to ask Cummins what is needed. 2003 Neptune ISB300, 36' Thanks for for the help.

Many years ago a good Ford machanic told me that Ford said not to bother changing the Serpentine belt until ti started loosing rubber from the inside of the belt. Many people worry about them when the stare to crack on the inside. He said don't worry about those cracks.I've never lost one.

If it gives you peace of mind, carry spare. I have NEVER lost a serpentine belt in over 40 years of driving.

If you have the ability and tools to change it on the side of the road then carry a spare. If not why bother?

Roger10378 wrote:If you have the ability and tools to change it on the side of the road then carry a spare. If not why bother?Sometimes it is easier to find service help than parts. Especially at late hours or holiday etc.For the OP: Have the belt changed at your next service. Save the old as a spare. Then you know it fits.Generally I believe minimum life on these is 10 years and 100,000 miles. So unless you are approaching that I would not have any concern yet.

dalenoel wrote:Is it better to measure the one on the coach or to ask Cummins what is needed. If the labeling is gone take it off and buy the exact same one. Cummins may not know what belt you have due to Monaco added equipment.

New Serpentine Belt? | Good Sam Community

Grit_dog
Navigator
May 18, 2021
Dusty R wrote:
Got to ask a question.
Has anyone had one actually break? If so, how many miles did it have on it?

Never seen one break that wasn’t the result of some other failure, taking out the belt.
Old habits I suppose, but a new belt and idler and tensioner pulley on an older or higher mileage vehicle is cheap insurance. Which I realize sounds silly if not replacing everything that spins like the alternator and steering pump. But...
Grit_dog
Navigator
May 18, 2021
dalenoel wrote:
I'm going to see if the labeling is still on the belt. Need to get into the closet to get access as this is a rear radiator. If not then will have it changed at next service.

To some who suggested the results of a pickup truck, this is different in a rear radiator as there is no hood, easy access or ability to work easily. You need to stand on your head in a closet or be under the engine reaching up.

Not being sarcastic but just realistic.

Sounds like even more reason to replace it pre emptively then. If it’s original.
1320Fastback
Explorer
May 18, 2021
I've had serpentine belts break at work before. Our equipment has Cummins 3.8L diesels but is a rare failure. Never had one break on my personal vehicles since they got away from V belts.
agesilaus
Explorer III
May 17, 2021
I did but it was many years ago and I don't even recall what car I was driving at the time. It was one of the old V belts. I assume the engineers have improved the product since then.
Dave_H_M
Explorer II
May 17, 2021
Good question Dusty. ;)
Dusty_R
Explorer
May 17, 2021
Got to ask a question.
Has anyone had one actually break? If so, how many miles did it have on it?
dalenoel
Explorer II
May 17, 2021
I'm going to see if the labeling is still on the belt. Need to get into the closet to get access as this is a rear radiator. If not then will have it changed at next service.

To some who suggested the results of a pickup truck, this is different in a rear radiator as there is no hood, easy access or ability to work easily. You need to stand on your head in a closet or be under the engine reaching up.

Not being sarcastic but just realistic.
valhalla360
Navigator
May 17, 2021
1320Fastback wrote:
Before our big trip a few years ago I changed the belt on my truck myself a few days before departure and kept the old one as the spare. I do not agree with waiting till is starts shedding rubber because that is what will leave you stranded.

Maybe if you pop the hood every time before you start the engine waiting for it to start shedding works...but I know no one who does that, so we did what you did. Put the new belt on and kept the old as an emergency spare. No sense buying a new belt and then let it age out sitting in storage.

Plus if you do it at home, you get an idea of what you need and how to do it, so if it does fail, you are better prepared to replace it.
Grit_dog
Navigator
May 17, 2021
Idk if the other ISBs are like the Dodge trucks, but the dodge Cummins don’t love anything other than OEM or Gatorback, now Continental, belts. Others work but they are finicky, squeak and squeal in anything other than ideal conditions.
Food for thought if you’re replacing it.
1320Fastback
Explorer
May 16, 2021
Before our big trip a few years ago I changed the belt on my truck myself a few days before departure and kept the old one as the spare. I do not agree with waiting till is starts shedding rubber because that is what will leave you stranded.

If they make on I suggest the Gates Green Stripe for your rig.

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