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Bus Leans in Front
Howdy Guys;
I need some advice. The front of my bus leans towards the passenger side a little. The passenger side is 2 inches lower than the driver side at the Steer tires. The bus is level in back at the Drive tires.
I just noticed it today after returning from Prevost-Ft.Worth for a Level 3 Service and Air System check. They repaired a few small leaks in the compartment under the driver seat. I had all new air bags installed four months ago at Prevost-Ft.Worth.
Any ideas what I need to look at or why one side is a few inches lower than the other, but only in the front? Is it safe to drive in this condition?
The bus is a 1999 XL-40, Country Coach.
Thanks;
Michael
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12 Replies
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Michael, if your coach leans towards the passenger side a little in the front your problem is not in the front, but in the RH rear.
Having said that you need to provide more information. Does it lean when the bus is fully aired up and running and the level low switch is in the driving position? Or does it lean after a while?
The leans is such a common issue, especially on older coaches due to aging it helps if you can go to the articles section on this web site and read those articles that relate to the suspension so you have a little better understanding of where to begin looking for solutions to problems.
If you do have any air leaks no matter where they are it is important you fix them. They may be related to this problem or they may be part of a completely different problem. One thing we are having a considerable issue with lately is owners are finding their air systems have not been well maintained and moisture has gotten into the systems and it has damaged them so normal trouble shooting in some cases is no longer valid.
You cannot assume new air bags rule out them as a problem either. An air bag can leak even if new or the fittings can leak. Your vintage coach has separate “ping” tanks and they can leak, or the whole issue could be as simple as the mechanic that did your recent service knocked a ping tank valve slightly open.
If your coach is equipped with the HWH leveling system it needs to be turned off or in some fashion disabled because if it is trying to keep the coach level it is masking the origin of the problem.
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Jon, the bus leans when the bus is fully aired up and running and the level low switch is in the driving position and stays that way after it stops running.
I just checked it again and found it had maintained the same height after 16 hours, however, the Aux Pressure had dropped 40 psi and the Brake Pressure has dropped 50psi.
Michael
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actual air bag height of inflated air bag on each side front. Should be the same. Aprox 11 1/2 inches if memory serves me correct . Your coach falls into a unit number change over where Prevost used 2 norgrens on some coaches on front end. Check your against the prevost.com web site ; just enter your last letter in your serial # and last 4 didgets. FWIW . Will help problem solving with these two pieces of info. Bob
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Bob is right. I think it is actually 11″ between mounting plates on the air bags +/- 1/4″. But that means based on the fact the bus is aired up and running that your ride height valve in the rear on the low side needs to be adjusted.
You can do that yourself if you promise not to get beneath the coach. If you have to get beneath it block up under the chassis support points. If I remember you can look up just ahead of the drive wheels in front of the fender liner you will see the valve and adjustable rod on the end of the ride height valve arm. I think yours has instant acting valves so keep in mind anytime you work on the suspension the coach can drop all the way down and in your case that might happen pretty fast so use extreme care. If you are not sure let Prevost work on it.
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I am assuming it is low in the rear also. . It seems odd, but if it low on the front corner but not low on the same side in the rear, look to see if it is too high on the opposite side.
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Jon, the bus is only low up front on the passenger side. The driver side up front is the same height it has always been. Are the air bags specific to their location and have different heights? Could there be something not allowing the front bag to fully inflate?
Michael
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How many norgrens are down stream of front leveling valve on your coach( between air bags and leveling valve)? Has this problem started since the air bags have been changed? That is why I ask about measurement. There is two reasons if your rear is set correctly the front could be off. the first is if you have the two norgren system(prob not) the second is wrong air bag on one side—If both have equal pressure but are differant sizes they will carry a differant load. You don’t even want to think about the other IFS suspension problem.. check the easy measurements first.. Be safe and stay alive..I did assume by the year mentioned you have a IFS suspension.. If you want to share your Last letter of your serial # and last 4 numbers . I will check .
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The problem began after the new air bags were installed. I do have IFS. Using the serial # and last four numbers does not work since it is a pre 2000 bus. I am looking at drawing d140237rb. It corresponds with my year model and serial #. I cannot tell how many norgrens are downstream of the front leveling valve.
Michael
1999 XL-40 Country Coach
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works great on my 98 45 Xle that is how i found about the two norgrenson some later units. Use the Mth destignation and leave year blank. Mine is W- 6553 W=1998 6553 =unit number I use mth as bus type. ? do you have the kneeling option
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on that corner.. Should be 1R 12-337 or prevost # 630151 12inch diameter is key factor here for measurement.for a ifs coach! on drive bags are 1 r 11-088(11.5 dia) and on tags 1r11 096 (11 dia) Source prevost tec public for Ifs suspension mid 1999. Bob
air bag height from prevost 11.7 inches of Ifs coach.
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I am not so sure what trade number or Prevost part number air bag is required on the front of your ’99 CC,
But if you have the pneumatic drawing for your coach I think you have two Norgren 3 port valves and it is possible one is not functioning. I don’t know if you have two separate ride height valves in front. But if you are sure the rear on the same side is at the right height then you could have an air bag issue with it being an incorrect size (something that has happened in the past) or an issue with the valves that participate in controlling the height. I will look at my pneumatic diagram to see what I have and how it is all tied together.
Roughly speaking the distance to the ground from the bottom of the bay doors is going to be around 11″ more or less. Your chassis is not going to twist so if one corner is low, the opposite diagonally is going to be high or the one on the same side is going to equally low.
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When I look at the Prevost Technical Publications page, Pneumatic Diagrams Index, there is no where to put in my “X” and last four digits. I did leave out my year and came up with a diagram that fits my coach number and year.
My bus shell fits the second from the bottom box. A Bus Shell XL-40 (M) with IFS. And I am within the shell # range. I am assuming the (M) means motorhome.
I think I see two Norgrens downstream from the air bag. I only see one front ride height valve on the drawing.
Prevost Ft.Worth just called and said the passenger front air bag was lower than the driver front and made the adjustment. They also replaced a “Berkett” valve on the Tag Axle, as it was original and had a slight leak.
Thank you for everyone’s help. I am out of computer range fro the weekend, so I will update you Monday on any other progress.
Michael
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