Starting proceedure

[adamdegraff]

Hey all,
a quick question about starting a coach. A while back, I read a post the said that you should turn on your aux air compressor to bring the coach up to pressure, thus tensioning the series 60 belts before starting. The question is: is this always/ever necessary? I would think that if this was always a necessity, that prevost would have put some sort of pressurizing switch at the con. At the same time, after a coach has been sitting for a few days, certainly it seems like a good idea. In fact, just the other day I was looking at my engine and noticed that one of the group of three belts that loosens had fallen off the pulley. Obviously, I just put it back on... no problem.

Any thoughts on this subject? Does everybody always "pre-pressurize" their coach before starting?

Thanks,
~Adam

[Jon Wehrenberg]

I never "prepressurize" my belts. I also have never had one fall or jump off so I am not sensitive to this issue.

Prevost makes a lot of coaches that use all sorts of belt configurations. Some have OTR air, some have multiple alternators, and I have seen some with multiple alternators and driver's air. We on POG probably represent a minute percentage of Prevost operators, and of the Prevost operators out there in the real world a very small percentage have auxiliary air compressors.

Where I am heading with this is that if the belts come off when the aux air system has little or no pressure there is a problem. I cannot imagine a charter operator driver having to mess with belts that jumped off. Whatever is causing that problem would soon be corrected in the real world.

Since several POG members have made it known they have had an issue with belts jumping there is likely a problem, and the easy solution is to air up the aux system prior to start. The less easy solution is to try to figure out how to align all pulleys, especially since there is no easy way to sight along them to look for anything misaligned.

[Ray Davis]

When I purchased my Marathon I spoke to them about this issue. They specifically told me to turn the ignition key, and wait around 5 seconds, to allow the pulley tensioners to tighten up.

Now it may seem that Marathon intends the aux compressor to be always on. In my Marathon, the only way I could find to turn it off was to actually flip a circut breaker.

If I remember correctly, Kevin Erion had made a modification on his coach with a "set bolt" to not allow the tensioner to get so lose as to allow a belt to be thrown, even if starting without air in the aux system.

I never had an issue on my coach, but there was always some little bit of pressure in the aux system, and I did the 5 second wait as instructed.

Ray

[Joe Cannarozzi]

The old style tensioners had a internal spring that did not allow slack after the air pressure dropped.

I can not figure out why they got away from this??????????????

[truk4u]

Adam,

My 97 Marathon had no aux compressor and would leak down over time, but I never tossed a belt. Being anal, I would air it up manually when at home. Jeep on the other hand has had his belts thrown.

My CC has an aux compressor and it only takes a few minutes to build up 50 PSI, enough air to tighten the belts.

If you have an aux compressor, run it prior to starting. If you lose no aux air pressure over time, welcome, you are in the POG book of records!:p

[merle&louise]

Would it be possible (or worth the effort) to replace the air bellows with spring tensioners?

[rickdesilva]

I had a re-occuring problem of one of the 3 bolts holding the tensioner assy to the engine breaking off. I couldn't figure out why this was happening, so now before I start up I pre-pressurize the system and so far no problems. So it certainly can't hurt to pressurize the system before you start.

[jello_jeep]

My belts came off one time, after being driven by a Marathon driver transporting it from Mira Loma to Beaumont.

If it sits for a few days, or is otherwise de-pressurized and the belts are completely slack, you have plenty enough slack to remove them if you so chose. Starting your engine when they are completely slack will cause unpredictable results. I don't see it as an alignment problem at all.

The the air comes to pressure they come taught fast with the engine turning and the other pulley stationary, and sometimes more than one belt side by side, things could happen.

Safe money says either install a "stop" like Kevin E did, or just air up... Gives you another 60 seconds or so to admire your wife and shower her with shameless compliments, as I do so often.. (Remember they can read this stuff now)!