[Corey]

Richard.

Worry not.

Think about this: A seated coach has no provision for airing up prior to starting up so when they sit for a long period and the aux pressure goes to zero and the belts go slack, the driver just fires the coach up and once air pressure builds he is good to go.

Unless I am working on my coach or it has been run recently after sitting for weeks I have no aux pressure. I never air it up with my shop air. I just start the engine, let it idle for a period of time, go to fast idle and watch the pressures build. I have never had a belt issue.

Your coach should have a check valve ahead of the belt tension release valve. If that isn’t working very well your belt tensioners will lose pressure as the aux system loses pressure. A common problem is the regulator or the belt tensioner valve will leak. The regulator leak might be corrected by tightening the screws around the housing. But even if you don’t correct the leak don’t worry about loose belts.

[John]

Mine go flat sooner than that and I have replaced all of them during the last few years. When I remember I use the aux compressor prior to starting but I can attest that I have started it many many times with the bags flat and have had no issues with belts flying, etc.

[Alvie]

I have been chasing air leaks ( with a lot of help from Jon Wehrenberg) and one of the leaks I found is the pneumatic valve that turns the air on and off for one of the belt tensioners (there are two of them mounted on the rear compartment wall next to the rear eletronics compartment). I have been using the bubble solution that kids use to blow bubbles as it last longer and is easier for me to see the problem.

[Roger]

After starting the engine at low idle to let the air pressure build up to 60 PSI then I turn the high idle switch to on that will prevent the belts from flying off the pulley.

[Dean]

Hish,

You might be scaring people by suggesting they need to wait until 60 PSI to keep belts “from flying off the pulley”.

Assuming the coach air pressures were all very low or at zero the aux air system will still be at zero when the brake systems reach 60 PSI. The aux air will not begin to fill until around 75 PSI. I am not aware of anyone throwing belts unless they have belt alignment issues to begin with.

[Wayne]

When you are ready to go, start the engine. Exit the bus to make your walk around inspection. During that time if the belt tensioners have relaxed, when sufficient air builds you will hear a short squeel and hear the air rush from the fan. Procede to the engine doors and open them and take a visual of all operations. If anything is awry turn the engine off and correct the situation. Do this everytime before you start and you will not have a problem.

JIM

[John]

If all the fittings, air bags and regulator are leak free, it’s likely check valve. I have had 2 mid 90’s without check valves installed, I did my own. Air it up with the Aux compressor before staring, you may have to have the key on, you didn’t tell us who the converter is.

[Dean]

I still find it hard to believe that the belts will just slowley tension without ripping them apart, but all the responses are to the contrary. After I purchase a set of belts to have as spares, will try as all of you have indicated. Will let you know. Also will try to find the leak in the valves. More to come and thanks again!

Richard

[Mark]

Richard,

For what it’s worth, I always verified that I had adequate aux air pressure prior to starting the bus.

Even with a spare set of belts, I didn’t want to risk starting the engine without the belts properly tensioned.

Perhaps unnecessary, but I saw no downside to playing it safe.

And, I never had a belt problem in 6 years of ownership.

[Mark]

All of my Liberty coaches over a 23 year period had pneumatic belt tensioners. Every single one of them had belts go slack over time. With rare exception I never aired up the coach prior to starting. I never threw a belt.

My concern is where everyone is focusing. How many of you that took pains to air up your aux system such that the belts were tightened when you started the coach are as dedicated to doing a pre-trip brake test? Or a tire pressure check? A light check? I cannot offer any advice on belt tensioning on non-Prevost installed belts such as some converters who add their own AC compressors or alternators, but Prevost does’t suggest airing up the aux air system prior to start.

[Rick & Denise]

I am in need of a new fan, blades with big chucks out of it. I was wondering if this had something to do with a loose fan belt. No idea how this happened and I see no other signs of damage. It’s a good thing these fans pull air and not push air thru the radiator.

[Peter]

Greg, I am going by memory now, but I seem to recall around your vintage Prevost made two changes. First, they made the plastic bladed fan a replacement for the very heavy steel bladed fan originally installed. They also installed a travel limiting device because it was determined if a fan belt broke the fan could contact the radiator.

What you describe however is fan belts are in place which means they are going to limit the ability to contact the radiator. Could the damage be caused by the fan contacting the shroud?

[John]

yes, but I don’t know what caused it. How difficult is it to replace the blade? I have wondered if I had the valve switched to the off position, but they are no pieces in the driveway so it must have happened on the road.

[Archived]

The only way I can imagine the blades hit the shroud is if there is “wobble” in the blade shaft due to bad bearings or something loose.

As I recall the blade removal was easy with just several bolts holding it in place.

[Mike]

Greg,

On mine the fan drive has to be moved out of the way or the fan would not come out of the shroud.