[DON]

Thank you to all who offered help on this query. Turns out the belt I originally ordered 12PK1875 / K120738 / Dayco 5120738 which is the belt the Prevost spec identifies WAS the RIGHT belt. What was wrong was the belt I got from Amazon “Warehouse Deals” was made or identified wrong. The sleeve had the right number on it, the right number was inked on the belt, but the belt was not the right length, was too long by about 3/4″. I sent it back for refund. Maybe that is why it was a “warehouse deal”.

Got another of the same part number belt, put it on, fits just right.

Meanwhile my original post mentioned a prior shop or owner had put some AX75 belts on the engine to fan gearbox drive instead of the correct AX74. I cited there appeared to be “no ill effect”. Upon looking at things the other day when replacing the alternator and AC belts I spotted the wear spots on the coolant pipe in the photo below. In time these over long and slack AX75 belts could have worn through the pipe and created a bad day.

[glen]

David,

I avoid the issues of identification by maintaining an active account at Prevost Parts which can be set up easily. I provide the bus number, etc. when I call… Last week, we were at an RV park and I wanted to change out the three AX 74’s and I requested matching belts. It is normal for the belt manufacturers to state the tehnology is so good, they do not need to match… WRONG…

Prevost sent me two sets they matched and bound each matching belt set together….cost $12 per belt and they delivered to the park overnight at their expense…. sent me the electronic bill… and all is well.

Pres

[DON]

David, please verify this with someone but if your fan belts are too long it might possibly let the fan move to close to the radiator and really start a bad day.

I think there may be a steel stop welded on the brackets some where to keep that from happening.

I will go out and look at mine but check for your self that the fan can not get into the radiator.

[Harry]

Belt#AX74 is correct for my bus. I can get about 3 fingers between that water pipe and my belts.

I think there’s an internal mechanical limiter built into the little tensioner airbag not allowing the fan close to the radiator.

[glen]

Thanks. I have no doubt the AX74 is the right belt. Just was commenting someone prior had put AX75 on it and it allowed enough slack to rub the pipe. It looks like your pipe runs a different path than mine. The spot where mine rubbed when the wrong belts were on was down low below top of bumper level where the pipe elbows and dives down and goes forward to the lower part of the engine or maybe it goes/or comes from the trans coooler don’t remember for sure.

[Jackson]

Not unusual to have the coolant pipe marked up from the belts, just start your bus from the rear with no aux air in the bellows and watch what happens.