The Leans

[Jon Wehrenberg]

Under the POG III thread Ben suggested a session on the leans. Trying to trouble shoot or identify what specifically is causing your coach to lean is like trying to define how high is up.

When your coach leans it is because you are leaking air.

End of training session:D

The leans begin when your valves start to leak, or your air bags start to leak, or it gets cold outside. All of the causes can be addressed but there is no simple way to explain how to fix your specific problem for a number of reasons. The primary reason is because your converter may have handled the leveling system on your coach in a manner different from my converter. Another reason it is not so simple to identify a specific cause is because there are so many places that can be a leak source and every one of them can be the problem or only one of them is the problem.

Several on this forum have had success dealing with the leans. Maybe we can accumulate the advice here and get Ben started on his quest to solve his problem.

[MangoMike]

I'll be glad to add to the lean quest.

I'm on that mission now and have replaced most my Norgren valves and hitting the last couple today in an effort to stem a rear leak. It's probably the most persistent problem that faces Prevost owners, well at least the ones 5+ years old. And Jon is right there is no simple fix, you just have to be persistent and keep on tracking them down. I'll be real interested in seeing Jon's final evaluation on his new snifter.

I'm doing my best to fully understand the whole system, it's relationship to Norgren valves and converter vs Prevost installs. I'm hoping with that knowledge it will be easier to understand the nature of finding a particular leak.

Will keep you posted.

Mike

[dale farley]

I started my search for a leak today, and I found one of my air bags that is leaking when it has maximum pressure on it. Unfortunately, it is on my tag axle, so I assume that would not cause my coach to lean. I also used some ramps that I made a couple days ago. They are made from 3/4" plywood and seem to work fine. They give me about 10" more clearance, so I can do most things with this much working room. I made a couple pictures if anyone is interested.

I have noticed my coach does not lean all the time. It seems to be worse when I raise the right side up to its maximum height. I stayed under it for several hours today and noticed no significant drop on either side. When I quit for the day, I raised it to the maximum, and it has dropped about 3/4" on the right side in 1 1/2 hours. There is definitely a difference in where I leave my level switch as to what happens. There have been times when I have leveled the coach and it would drop several inches on the right side in just a few minutes.

One thing I don't understand is why it drops about the same both front and rear unless I have a leak in both places. In the last 1 12 hours it has dropped about 3/4" in the rear and a little over 1/2" in the front. Does this mean I have a leak at both ends or is there a leaking valve that is common to both ends?

Although I could easily see the leak using a bubble mixture, I could not hear it using a hose as a stethoscope. It only leaked while the pressure is at max, then it tapers off to almost no leak at all. I have ordered one of the ultrasonic leak detectors like Jon is using, so I will let you know if it helps in my quest to find all the leaks. Dale

[MangoMike]

RR,

I've been spending a lot time under da bus trying to full understand the whole level low system. So here's a couple of thoughts. Which may or may not be true, but it's what I figured out so far.

This pertains to the 97 liberty xl classic:
Front air bags and rear air bags are totally independent of each other in the Level Low mode.

There are 5 norgren valves handling the rear of the bus. Two in front of the drive wheels (center coach) add air to the rear bags - one for each side. These are 5 port valves.

718

In the cavern between the drive and the tags on each side wall are 3 port norgrens. One for each side. This dumps the air from the rear bags. There are 3 bags on each side in the rear, which includes the tag. I'm not sure if the three are all ganged together. I know the two by the drive wheels are. The third three port norgren on the passenger side is some sort of control valve that works the spool valve in some of the rear main norgrens -not sure at this point which ones.

719

Left one is the dump valve and the right is the spool controller.

I'm going to get a handle on this yet.

Mike

[Joe Cannarozzi]

Roadrunner
The front drops with the rear drops on one side or the other when it leaks because the front has only 1 height valve dead center. If ya think about that for a minute you'll get it. When the front leaks that will never affect the rear.
.

[MangoMike]

Joe is correct The front bags have only one ride height valve for both as you motor down the road.

722
Ride Height - 1 up front, 2 in the rear

But the Level Low system employs at least two Norgrens up front, one for each side.

723
Located in the steering bay.

Again all converters different as to their approach to Leveling. This is Liberty's.

Mike

Note to Harry: I'm trying to use the site as intended ;)

[dale farley]

Well, from what Mike and Joe are saying, I assume my problem could be caused by the leak in my one rear bag. Of course, I am not sure if the tag bag is ganged with the other two bags on each side. I really wouldn't think it would be since it has to operate rather independently, but maybe it is.

Mike, are those valves in your pictures the Norgren valves? I have read every book I have and no where do they mention a Norgren valve. Is that just the brand name for the control valves?

[Joe Cannarozzi]

I am curious. Our 86 does not have these norgrin valves and the bus functions just fine without them. I believe we have all the same capabilities as the busses with them, the ability to level the bus while camping with the suspension. Were these components added just to complicate things or what:confused:

[MangoMike]

Dale,

Honestly I don't know if the Tag are ganged with the rest or not. It's something I would like to find out to add to the understanding of the system.

Norgrens are a brand name and the photo of the two valves are the Norgrens.

Joe,

I'm not sure when/if any changes were made. My knowledge base is solely limited to my Liberty at this point.

But the person who unlocks the Rosetta stone about the whole leveling airbag system on theses busses is going to be one popular guy on POG. I nominate Winchester - he's got plenty of free time to be poking around the belly of the beast.

Mike

[dale farley]

Joe, I am thinking the same thing about my 93. I don't think I have any Norgrens, but I do have a leak. Dale

[Joe Cannarozzi]

The only time the tag is independent is when you dump it otherwise it is controled by the ride height valve on that corner that also controls the drive axle bags. While camping if the tag bag has a leak I'm not sure if the drive bags will go down with it' or visa-versa, or if they are isolated from each other. I know an easy way to find out though. Wait for Jon to read this:D
And Jon how about my previous question about those useless norgren valves?

[dale farley]

This is a picture of the ramps that I used to get under the bus. I got the plans from one of the Prevost forums. I was a little leary at first about how safe they would be, but they seem to be very sturdy and stable. I intend to build a pre-ramp from plywood that will be about 36inches long and 3 inches high. I need to run the wheels on these prior to placing the ramps under the bus. Dale

[MangoMike]

Dale,

Nice ramp. How many sheets of 3/4 did it take?

Also your wheels are lookin' good. Nice and shiney.

I saw your leaking air bag, the good news is at least you've identified one source.

Mike

[Navigator]

MM,

The Consumer Electronics Show is loaded with lots of new gadgets. This Caddy show car is being used to display new sound devices.

Looks like the Level Low System needs some work!! But how do you get under it to work on it??

[merle&louise]

Dale,

Nice plywood ramps. About how much do they weigh?

I saw the handles on the sides and was wondering how heavy they were to lift up and move around. They sure seem safe. Good post.

[dale farley]

Mike, I used 11 sheets of plywood, 3 pounds of 2 inch sheetrock screws, 14 tubes of liquid nails, a bottle of wood glue, and a couple pounds of 16d spiral nails. Because my exhaust pipe hits the ramp when I try to slide the ramps under the left side of the bus, I used another sheet of plywood today and made 2 short ramps to get the wheels off the ground enough so I can slide the large ramps under the bus.

I am not sure how much the ramps weigh, but each one of the four ramps has almost 3 sheets of 3/4" plywood. I can pick up either end and move them around pretty easy. When I want to move them very far, I use a dolly. The handles make it much easier pulling the ramps from under the bus. They also make it easier to lift the ramp enough to get my hands under it to move it. Dale

[Jon Wehrenberg]

Dale,

If you have a leak in any portion of the rear system it will affect one side. A leak in a tag air bag will cause the rear to drop because it may leak air pressure from the other bags on that side also (I said may, not will), but for sure the coach will lean even if the leak is confined to the tag air bag and none of the other air bags just because the rear will drop because the tag axle weight must now becarried by the remaining air bags. I'm tired. I hope I said that in an understandible fashion.

Joe is not totally correct about tag axles air bags. On his coach, my 1987 coach and likely most 40 foot coaches tag axle air gets dumped manually. On later model 45 foot coaches a sharp turn at low speed will automatically dump air in the tag axle airbags to reduce scuffing and to sharpen the turn. Any time air to the tag is dumped the tag axle brakes are inoperative.

Mike has posted some of the Norgrens and identified where some of them are. Your coach may vary, but there are Norgren valves located ahead of the drive axle fender liner and I believe there are four and possibly five Norgren valves in the steer compartment on some coaches.

If someone who is a computer graphics whiz would volunteer we could start a project to diagram Norgren valve locations (by converter) and as we get information identify each valve as to its function in the air leveling system. That alone will pinpoint which valves to focus on when trying to dea;l with the leans.

One final note...Fast Roger and I played a little today with the ultrasonic leak detector. His front end has been dropping so we did a little playing with the leak detector. We believe we have isolated his problem. It took about 30 seconds. We both listened and both believe that is the source of his leak and when Roger gets it fixed I hope he will report to us all. If we were correct we will have just proven that a $322 expenditure will save hours of speculation.

[Jon Wehrenberg]

Joe,

I have not seen your leveling system so I don't know what you have or how it compares to ours which are based on Norgren valves.

[dale farley]

Where is the best place to buy a new bag? Is the replacement something that I should be able to do by myself? Dale

[MangoMike]

Dale,

Over at www.Prevoman.com there's a couple of HOW TO's on changing air bags. I did a front one and Jon & Roger show how to do the rears. We purchased the bags directly from Prevost parts. 800 621-5519

Mike

[Jon Wehrenberg]

Dale,

Roger and I just replaced all the air bags on both our coaches. I ordered mine through Prevost in Elgin. I spoke to Charlie Kailor who is very helpful.

I also shopped airbags from other sources and hands down Prevost is the source of choice on airbags. They stock them, the price is right, and you will get the correct one if you are specific as to what coach you have. Make sure your Prevost serial number is available when you talk to Prevost.

I replaced the air bags on my 40 footer years back, and I don't think there are any "gotchas" except if I recall the rear drive axle bag removal can only be done if you remove the shock absorber. Not a big deal, but necessary if my memory is correct. Air bag removal on a 45 footer is easier. The fronts should be modified to make removal easier and future replacement a snap.

I have a single observation about air bags based on what appears to be anecdotal evidence. They likely have a life span of about ten years. On my first coach that was when the first failure occurred. It has happened on Mike's and Roger's coaches also. Both are in the 10 year age range. Because of that, as preventive maintenance I would strongly recommend that any airbag that is 10 years old should get replaced.

An on road failure of an air bag is a show stopper. You might be able to drive to the shoulder, but you won't get much further if the air bag fails catastrophically, and if the air bag failure is a leak and not a blowout, that leak will only get bigger, and at some point your compressor will not be able to overcome the air loss.

[dale farley]

I willl order the air bag from Prevost also. One of the problems I have is that I don't know the repair history of my bus. I can see that there are replacement parts, but my records only go back to last year. Everything seems to have been lost from the original owner. I suppose I can get what was done at Prevost, but many people have repairs done at independent locations.

It will probably be a couple weeks before I actually replace the bag. I am waiting on Prevost to get my account straight before I purchase anything else. I ordered an air dryer cartiridge in early December, and they shipped the wrong part. They then shipped a replacement part overnight which was also wrong. At this point, I have paid $208 for two wrong parts and still have nothing to show for it. I am waiting on my credits to come through before I make additional orders.

Once I replace the bag that I know is leaking, I intend to use the leak detector to check all fittings, bags, and valves. I do have some Norgren valves in my steering compartment and maybe under the bus as well. Thanks to all for your input.

[Jon Wehrenberg]

If I heard it correctly, Prevost retains service information by serial number. If they serviced your airbags in the past the records should reflect that.

They do that because they warranty their work and that warranty follows the coach, and not the owner.

I don't know how well equipped your garage is, but each air bag has a date on the label. All you need to do is drop the top of the airbags down enough to be able to see the label and you can determine the age. It is a lot of work, but at least you will know where your stand.