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Around fittings for oil trace or signs of dirt/oil accumulation=sometimes is sign of slow leak that draws dirt to it. Also around seals on compressor. Should be AC clutch relay in rear electrical box-make sure it is good. Power to it and out when signal recieved. Your light on dash is probably correct but if compressor is not running there is no pressure to read. Again just trying to think thru your problem. Good luck. Might ck with a local charter company–they are usually glad to help and well equipped. Bob

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One of my switches on the battery bay door had a rubber band on it . This may be te bad one thanks David

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Jon,

How about at the campground, if not on the road. We could park in the back of the park and wait until the office closes….Just kiddin’

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For those with an XLII, there is some great information sharing going on in pup about demaination and how people are handling the problem. Ive learned a ton.

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I hope I don’t have to remember that in two years when it’s due again. Hopefully they just do it, maybe with a flush and fill?

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Jim is correct about how to remove a front air bag on an IFS coach.

The bus was on stands and even the shock was removed (for changing) so the suspension was at its lowest point. We took the cotter pin and castle nut off the ball joint pin so we could push the threaded portion of the A frame ball joint threaded end up to raise the A frame to get the needed 1″ more space.

I put a 4 ton porta power on the bottom of the threaded portion and the (what I assumed was a tapered) pin would not move. I am sure it was rusted in place and I was reluctant to beat the hell out of the A frame to loosen it. On my coach I will do whatever was necessary, but I didn’t want to beat on someone else’s coach.

When I change my air bags I am going to use a 12 or 20 ton jack to pop it loose if the 4 ton porta power and beating with a sledge doesn’t get the job done. The only thing that makes it possible to use a porta power or jack is to take the brake chamber off.

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Thanks Jon for that explanation. One I am sure you have given many times. Primary and secondary both have to do with brakes- all else is aux. I read the DOT requirements and will run that test. You should consider writing a primer called “So you have a Prevost – Now what?” I am sure you and others have the material right here – just not in book format.

Wave

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Wave, Good information.

For those who are not yet familiar with how our coach air systems are plumbed and what the gauges tell us, here is a brief overview.

We have three air systems, primary and secondary brake circuits, and an auxiliary air circuit or system. All coaches show the primary and secondary brake circuit pressures on the dash. In addition low pressure in those circuits will trigger audible and visual alarms. When parked there is no pressure to the brake chambers and the parking brake is actually a very heavy spring that is holding the brake. If the gauges on those circuits drop it is not because there is an air leak associated with either the service brakes or the emergency brakes. The loss of pressure could be a bad or open valve on the air tanks, it could be a leak at the foot treadle or any number of other places such as at a relay valve. The two brake circuits should hold pressure for a very long time as in months, but it is not unusual when they drop after a short period of time such as over a few days. You definitely do not want them to drop in a matter of hours.

The auxiliary system can be large and complex and if we have leaks that is where they are likely to be found. Everything other than brakes will be on the aux air system. Prevost will have its suspension on the aux system. It will have the door lock, belt tensioners, and even air to the transmission retarder. The converter will also tap into the aux air system and everything from the floor slide to the generator air bags, and a multitude of other devices can be aux air powered.

At the very least, as owners and drivers all of us should know and understand how to do a DOT brake system check. That is the single most important part of the pneumatic system and a basic understanding of the air brake system will be very valuable.

Here are a few usually misunderstood conceptions about our air systems:

We do not need any air pressure anywhere in our coach to prevent our coach from leaning or dropping. Since the mid nineties when Prevost changed the operating logic air is locked into the suspensions when the key is off. If the coach leans, the leak is within a specific part of the suspension.

The aux compressor will not provide air to the brake system.

The coach has protection and check valves so that a catastophic failure of an aux system hose or device will not disable the brakes. However they are mechanical and it your responsibility as an owner to insure they are functioning.

Even if you properly maintain your brake system air dryer, and insure the tanks do not contain moisture, if you run your aux compressor frequently you have to insure its moisture traps or spitters are drained and working. Aux compressor air does not go through the coach air dryer.

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Jon and I were typing at same time. Hope you can get something between the two.

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Sid,

Call Marathon in Grand Prairie to get ahold of ..Seth. Washing and detail at any location. Seth has his own equipment including the “IO” water rinse.

Has washed our bus several times doing a great job including the toad. Fair and reasonable price.

AL

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I hope others agree with me.

I have changed several sets of air bags and Norgren valves over the years on my coaches and have assisted other owners doing the same thing. I have never succeeded in putting the coach back together so it is leak free.

There are so many fittings involved, so many potential places for air leaks, and the possibility the new parts themselves can leak that I have had to chase leaks until the coach suspension would not leak down. While I would be upset if I was paying Prevost or any other shop serious money to correct the leans, I can understand just how difficult it is to reach perfection.

Rule number one is to never re-use the push in fittings. They work great once. They simplify assembly. But over time as the seal ages it becomes a leak point. Demand that every single fitting that is part of the suspension be DOT compression fittings. And go one step further and demand whoever tightens the compression nut on the tube that he understands there is a specification regarding how many turns of the nut constitute “tight”.

The suspension can be leak tested one section at a time. Don’t move to the next section until the first has been leak tested. On almost all of our coaches we can pressurize the front, the left rear and the right rear independent of one another using the level low. It takes time, lights, mirrors and multiple ways to check for leaks but it has to be done. Sticking to one section at a time sharpens the focus. And no matter how careful I have tried to be I have come into the garage the next day and seen the coach lean over requiring me to recheck everything I thought I had done right.

Bottom line………..plan on the time it takes to do the job once, and then the time it takes to let it sit to verify it will not lean. When setting it up for a check do not raise the coach all the way up. Allow it to come to the driving height and use that as the benchmark for determining if the coach is leaking down. The rationale is to avoid over inflating the air bags. Unless the coach is unusually heavy the pressure in the air bags to bring them to ride height is much less than the bus system pressure. In my previous coach about 95 to 100 PSI brought the front to driving height and somewhere around 75 PSI put the rear at driving height. If the coach is raised all the way up it might take some more pressure but maybe not full air system pressure. But we tend to raise it and keep pressurizing the air bags. That means it will not lean until all the pressure above the needed pressure is leaked out. But if you start with just enough pressure to bring it to driving height, every drop of air that leaks out causes a minute drop in height so the leans become apparent faster.

And if you ever have the suspension system replaced (air bags and Norgrens) and it is returned to you leak free buy that mechanic a gift. He deserves it.

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Bob, you were clear in what you said. We just wanted to be sure for those who may not have been aware that over greasing the shaft could have serious consequences.

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Ha ha. When we stay in a Podunk RV park with lots of white box RVs we say we “over coach” that park. We liked the Fred Henne Provincial Park campground outside Yellowknife NWT. The KOA in west Glacier Mt is bus friendly and close to the park.

Grizzly RV Park in West Yellowstone is paved and spacious. There is also a new rv park in Driggs Idaho that looks nice on the west side of the tetons

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Buck Horn Lake, Kerrville, TX.

Le Hacienda RV, Austin, TX.

Grizzly RV Park, West Yellowstone, MT.

Tiger Run RV, Breckenridge, CO.

Hearthside Grove RV, Petosky, MI. or Signatures RV west of town.

Outdoor Resorts Pacific Shores, Newport, OR. Any Outdoor Resorts (FL, CA, OR, AR, TN, SC etc.)

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Tom and Jon, our thanks as well. Wonderful time! This was our first trip out without the kids and Claudia wants to do more, so it was either all of you she met, or hot breakfast in bed every day, likely both!! She was also worried I would talk “bus” 24×7 but soon realized that meant she had the RV all to herself to read at night.

I too enjoyed matching faces with posts – just two minor problems. First, I am horrible with names and second, I met many of you in the dark over too many beers!

It would be really cool if in addition to our avitar we could somehow associate a mugshot of each couple with our profile.

Right now we resemble that country song where the girl writing the singles advert asks the potential suitors to reply with a picture of their pick-up truck and dog 😉