[John]

I may be incorrect in this but it probably is not a “stretched belt” problem. Something is obviously out of whack that is causing this to happen. Check the foundation (bolts loosened, brackets cracked or broken?, etc..) Mine went out of line and it was the bracket holding the back of the radiator assembly as well as air pressure.

The fan was “leaning slightly” … after the coach got underway and higher RPMs were being experienced, the system actually was also losing pressure which allowed the fan to not be held firmly in place by the required pressure…. a couple of issues that are not hard to solve.

Pres

[Randall]

Thanks Pres, I checked all the mounting bolts on the bracket holding the fan, and the radiator. The shroud on the radiator definitely has way more clearance up top than on the bottom. Everything was tight, and had not moved.

I remember a few years ago, John at Prevost jax told me to put a bolt in the fan stop on another coach I had at the time, to keep the fan from leaning over to far, that they had seen a few do that, especially if the belts come off.

I’m going to try a slightly shorter belt, and see what happens.

[Fred]

Jerry,

Whatever you do try to not rely on a belt for a limiting device.

With all belts removed you should be able to move the entire assembly through its full range of motion and never have any physical contact with anything. If something does make contact the assembly needs to have its travel limited or the fan/clutch needs to be adjusted so you do not get contact.

Early 8V92 equipped coaches did not have a limiting device and belt failures resulted in the heavy steel fan blades used at the time to chew through the radiator core. Since then I believe all coaches have a means of limiting travel to prevent similar issues.

[Per]

Thanks Jon, I will not allow the belts as a limit device, but with the current AX73 belts, after they are used a while, I have no clearance left in the limit device from the factory. It is hitting the limit at the same time it scraped the shroud. It’s almost like the shroud is not perfectly round. The metal stop is just above/behind the bolt in the picture, you can see it has very little clearance left, and also you can see the metal dust where it has been bumping the bracket.

My wife says it’s because of the rough roads we were on! LOL she is usually right!

[Archived]

Just trying to help with a comparison, here’s mine with full aux air, new 73 belts. It’s been a few years since I removed the fan clutch on my Liberty, but I thought there was a little adjustment at the bolts to get the fan perfectly centered. Mine was hitting the fan shroud after my install when turning by hand and I had to make adjustments. Jon or Jeff?

[Archived]

That’s the way my other buses looked Tom, about the same clearance. This one has always been close, too close. The fan clutch has never been replaced, it only has 40k miles on it, and has never been in any damage. So I guess something was installed a little off at the factory.

[Larry & Diane]

I cannot remember if the fan / clutch mounting holes were elongated to provide some adjustment, but it would be worth a look. The way the clutch is secured to the mount probably has to be viewed with a mirror because you really cannot see the back side of it in any other way.

[Kim]

Have you verified the air pressure to the tensioners is correct? Pressure that is too high will stretch the belts.

Just a thought.

[Andre]

yes, 47 psi in bags Mikee

Jon I looked on the side you could see, no adjustment there, I’ll get the mirror and look on back side.

I remember replacing a fan clutch before, and don’t remember adjustable holes., but could be.

It seems like if the base of the big bracket that bolts to the floor could be moved towards the radiator, then it would tilt the fan back straight, and make the belts tighter too. I think any adjustments would be critical as close as everything is.

[Archived]

There is definitely not a lot of come and go because the fan has to have the smallest space possible between the blade tips and the shroud so it has the maximum efficiency.

[needtocamp]

Ideally the fan blade should be centered in the shroud with no more than 1/2 of the fan blades inside the shroud. This setup is not like automotive setup where the fan is buried in the shroud. Plus on the bus the entire fan blade should never be inside the shroud even at full rpm.

There is a little adjustment available wih the radiator/fan shroud assembly but not much. The stand on which the fan gear box is mounted should have a little adjustment available. The two legs that bolt ot he floor of the radiator compartment also have bushing in them that can wear and allow movement in the stand. If you can get a little adjustment of the two legs toward the engine, then the top tilts more toward the radiator. Then the belt length and the small air bag should position the assembly correctly and give you that needed clearance on the bracket shown above in the responses.

We have seen issues with the adjustment when the radiator has been removed and replaced. Generally the fan gearbox mounting plate is drilled for it to fit with little adjustment. I have heard and seen people enlarge the holes slightly to get a little movement in the gearbox and fan adjustment into the shroud.

[Richard]

Good Info,

I will check those items, especially the bushings, the radiator has never been out. Thanks Prevost service!

[Tom]

Here are more pictures of my coach showing the fan situation

First picture shows elongated adjustment holes, this is underneath the bus looking up at the fan gearbox brackets, only adjustable front to rear, not side to side.

on top side showing bushing for gear box/fan bracket, as you can see, nothing moved or appears to be wrong

the below picture needs to be rotated, but you can see with the AX73 belts, the fan blades are tilted over, making the top of the fan go to far into the shroud, and causing the bottom center of the fan to scrape slightly.

below shows the limit stop with very little clearance left, this is with AX73 belts

this below is the limit stop with plenty of clearance using AX72 belts, which are 1 ” shorter

AXX72 belts 1″ shorter

below with AX72 Belts, the fan looks like it should in the shroud, with an inch clearance all the way around, and barely protrudes into the shroud as Prevost suggested. And, is straight up and down along with the radiator shroud

Below is how everything looks with the 1″ shorter belts. 1/2″ shorter would be probably better, but they only offer that belt in 1″ increments. The mini air bag still has movement in both directions, there is clearance all the way around the fan shroud, nothing hitting anything or out of line.

I am going to try this setup. I’m sure some of you will disagree, since the belts are 1 number off, but I don’t see anything else to do. The limit stop remains in place, as it came from the factory. Only thing changed is the shorter belts. (Tom, turn the pictures that need to be please.)

[Harry]

I agree with what you have done and would only suggest you consider one thing.

With the 1″ longer belt the fan travel is at the extreme of the travel and it is against the stop. But you said in that position the blades hit the shroud. I would add something about 1/8″ thick to the stop so if the belts fail (a remote chance) there will remain a clearance. If you use something with a self adhesive such as a rubber pad or the flat wheel weights if you need to service something and need max travel you can always pry it off.

That entire issue could be that everything was assembled at the extreme and the build up of tolerances shifted everything to cause the problem and your solution is more practical than looseining eveny single component and shifting each one to the other direction. All the mounting holes have some clearance in them and I’ll bet there are a lot of parts that could shift just a little to create the problem.

[Archived]

Jon,

Yes, I agree with everything you said.

John Kincaid, back when he was alive, suggested to me on another coach, that I drill a hole in the stop, put a bolt through it, with a nut on each side, so you can add a little extra (adjustable) to the stop. Now that I have the extra clearance, I can do that.

He had said that they had seen a few hit the shroud if the belts come off.

My partner ordered this coach new, and I bought it from him 2 years ago, and I helped keep it up the whole time, so I know where it’s been, and this issue has been with it since new. We would just always keep new belts on the fan, because after a few months, they will stretch about a 1/4″, and get close to the stop

Seems like I allways get the wierd stuff to happen LOL.

Tom, look at your clearance after a few months, and see if it moves closer,,,,,,,,,,