Prevost leveling problem

[jok]

I have a 1990 Prevost XL that has developed a problem with the automatic leveling system. Before going down the road I raise the front and rear. Everything works normal. But when I go down the road the rear end slowly lowers. After raising it back up and parking it will stay at that position for weeks. It is my understanding that there is a valve I may need to replace and adjust. Does anyone know the location of the valve and how I would test it to make sure this is the problem? Thanks, jok

[gumpy]

I have a 1990 Prevost XL that has developed a problem with the automatic leveling system. Before going down the road I raise the front and rear. Everything works normal. But when I go down the road the rear end slowly lowers. After raising it back up and parking it will stay at that position for weeks. It is my understanding that there is a valve I may need to replace and adjust. Does anyone know the location of the valve and how I would test it to make sure this is the problem? Thanks, jok

I don't know anything about Prevost, but I don't understand your statement. You say you "raise the front and rear".  This doesn't sound like an automatic system. It sounds like you're using a manual leveling system to level the coach for driving. Does your coach not have automatic leveling valves?

If not, you need to describe your manual system for us, so we can determine what the problem is.
 

[jok]

The leveling system is automatic during normal driving. Raising the front and rear is part of the Prevost Level Low system. The Level Low is only used when parked. It allows you to over ride the automatic system when you want to level the bus when parked on uneven ground. The Low Level can also be used to lower the front to make entry easier. The problem that I am having is that the automatic leveling system no longer maintains the correct high or level when driving.

[Ace]

Yours must be different than mine. Mine airs up and away I go. I do have a kneeling option that allows me to lower the front while stationary and I can raise and lower the tag axle but that's about it. After sitting overnight, my coach is pretty level given the fact I must be on level ground!  It must have a leak for it to go down so quickly but when it's down, it's pretty soilid! It doesn't bother me too much as I'm getting used to it being this way! Never heard of an automatic leveling system. Your Prevost must be one of those big $$$ versions! 


Later...

Ace

[jok]

Here is the text from the Prevost Operating Manual:

"During driving, the conventional air levelling system of the vehicle controls the height at three points, the front, the left rear and the right rear. Your vehicle is equipped with a suspension system that consists of air springs (pressurized air bellows) located near each wheel. The amount of air in each spring (and thus the vehicle height) is controlled by automatic levelling valves that operate between the chassis and the axles of the vehicle.

The three (3) levelling valves are located as follows: one at the front which controls the amount of air in both front air springs, one at the left rear which controls the left rear corner of the vehicle and one at the right rear which controls the right rear corner of the vehicle. During normal driving, these valves work automatically to maintain the chassis at the proper level above the axles, no matter the road conndition or the vehicle weight.

When parked, and ONLY when parked, the level of the vehicle can be manually adjusted within the range of travel of the air springs. Thus, if the vehicle is parked on uneven ground, the manual override levelling system can be used to level the chassis of the vehicle.

After manual levelling, turn off the engine and turn the selector knob to the "DRIVE" position. The vehicle will stay in the levelled position (the air is "locked" in air springs) as long as there is no air leaks. The vehicle will hold this position for several days. When engine is restarted and adequate air pressure has resumed, the vehicle will automatically level for driving conditions."

When I am ready to start driving I normally use the "manual" control to raise the bus and then I drive away. While I'm driving the rear starts to lower more than it should, and to the point that it bottoms out. To prevent it from bottoming out while driving I have to manually add more air to the right rear and left rear air springs. This is a new problem. Until recently it would maintain the correct height. Now both the left rear and the right rear lower about the same amount.

Hope this makes more sense. Thanks, jok

[FloridaCliff]

Jok,

Yes it makes sense.

When you are in manual you can adjust up and down, no problem.

In drive it does nothing but go down by it self.

Sound like your leveling system is not providing any air in drive.

Switch or valve not working on after market system.

The rear slowly goes down when driving as the factory leveling valve lets air out to compensate for change in road conditions etc.

But in manual it airs up.

[Skykingrob]

Jok

Inside the last bay on the top back wall near the exterior door on the drivers side there will be a plate with 4 screws. The plate measures about  6"x6". Remove this plate and you will expose the left rear valve. By opening the main power cutoff switch door on the passenger side, you will expose the right rear valve. The front valve is located right in the center of the coach just slightly back and above the front axle and can only be accessed by jacking and blocking the coach. Because the front valve is so hard to get to and dangerous plus your concern is in the rear, I would start at the rear to check for leaks. One question before going further, do you start the coach with the level low switch in drive position and then the coach goes down as you drive? If you put the level low in manual position when you start and you have a leak in a hose/vavle, then the air will leak out and the solenoid will be closed that would normally be open to add air from the normal source when the level low is in drive position. If this isn't the case, read on.
1. Remove and open to access panels/doors as mentioned above.
2. Air up the bus in the parked position, then shut off the engine.
3. listen for any leaks, also spray the valves/hoses with a spray bottle containing a liquid soap/water mixture. if a leak is present, you
    should see bubbles. You can also go to a propane store to buy a leak detecting mixture they sell.
4. If normal, while the bus is still up, crawl on your side between the rear duals and the tag in just enough to visualize the
    two air bags on each side, all four should be fully inflated. BTW, you can crawl in there while the bus is down so safety isn't a
    concern but of course, you won't hear any leaks if air supply is zero.
5. Before jacking and blocking the coach to look at the front valve, check the connections on the level low switch by removing the
    panel near the drive that contains the switch, it may have come loose (although not likely with your description).
6. If switch okay, then jack the front according to the manual and block it according to the manual to check the front valve,
    although as mentioned, I don't think that is your problem. BTW, some coaches have a small access panel at the back of the spare
    tire compantment that allows you to access the front valve without jacking/blocking. Mine didn't
7. If all this fails, there are a number of solenoids in the level low that control air movement and a whole slew of hoses, so contacting
    prevost is probably your next best bet. As an alternative, call around in your area to commerical bus businesses until you find one
    that runs prevost. If you find one, and I am sure there are several in MI, ask if they will look at your coach. As another alternative,
    the shop manager at the Jacksonville Florida Prevost has been very helpful to me over the phone with problems. Other locations
    have been hit and miss for me. As one final alternative, there is a prevost owners site that has a bulletin board you could post to
    also, http://www.prevost-stuff.com, lots of years of prevost experience there as well as coaches for sale that you can drool over!

I have a 91 LeMirageXL with only 89,000 original miles. The right side used to go down in 2-3 hours. I found a leaking right rear valve, and an airbag hose that had a leak. Fixed both them by getting a new valve from Prevost, $38.00 and had a hose custom made at a local truck shop for $35.00. Front valve is still leaking so the front now goes down quickly but I haven't taken the time to jack and block the coach, lots of work and a safety necessity. Don't have pit in my barn, unfortunately, just gravel floor.

Hope this helps in some way.

Rob
91 LeMirageXL
Missouri

[Merlin]

I have a 1990 Prevost XL that has developed a problem with the automatic leveling system. Before going down the road I raise the front and rear. Everything works normal. But when I go down the road the rear end slowly lowers. After raising it back up and parking it will stay at that position for weeks. It is my understanding that there is a valve I may need to replace and adjust. Does anyone know the location of the valve and how I would test it to make sure this is the problem? Thanks, jok

Leave the Level Low switch in the "drive" position when airing up prior to motoring down the road.  I have the same system, and let it air up to normal elevation but due to the little hump in my driveway, I need to raise the bus up to the max level.  It will go about 4" higher, and clears nicely after I manually adjust the air valves.  When I clear the driveway obstacle, I return the switch to "drive" and the bus will slowly settle down to normal elevation by the time I get down the street and onto a main highway.  By the way, there is a flashing warning light that blinks when the transmission is in drive and the Level Low switch is in the "manual" position.  Does your Prevost have that light?  Mine was burned out when I purchased the bus.

[jok]

Thanks Skykingrob and Merlin,

My bus does have the flashing light that comes on when using the Low Level in the manual mode. On mine the light flashes when in Low Level mode even if it's in neutral. Typically I lower my bus a little to get in or out of the barn. After I pull out of the barn I manually raise the bus using the Low Level system. I need to raise it back up to prevent it from bottoming out on the gravel driveway (usually the rear center mud flap/air dam scrapes and the front Big Foot Jacks hit if the bus is too low). After raising, I put the switch back to "drive". I don't think my bus ever (since I've owned it anyway) raised on it's own in the "drive" mode, but maybe I didn't give it enough time. I usually drive for a while and adjust the level manually as needed. If my bus has been outside or when we are on a trip I usually leave the switch in the "drive" position all the time. Until recently it would stay at what seemed to be the correct height. Now the rear always lowers as we drive. When parked it will still stay up. Thanks for all the details on access to the valves. I am planning on checking it out this weekend. Also, I don't know if it matters, but this problem started while driving in 20 degree weather. The problem did not clear up with the warmer weather. Thanks again.

[Merlin]

... My bus does have the flashing light that comes on when using the Low Level in the manual mode. On mine the light flashes when in Low Level mode even if it's in neutral. Typically I lower my bus a little to get in or out of the barn. After I pull out of the barn I manually raise the bus using the Low Level system. I need to raise it back up to prevent it from bottoming out on the gravel driveway (usually the rear center mud flap/air dam scrapes and the front Big Foot Jacks hit if the bus is too low). ...

Appears you have the same needs that I do for getting out of the driveway.  My bus will come back to the normal ride height after the switch is placed in drive mode.  Yesterday I tested the bus air system by first switching the Level Low to manual then starting the engine.  It did not air up the bags at all even after high idle for 20 minutes.  Then I moved the switch to drive mode and it began to rise up on the air bags until they reached the proper elevation.  It must be working right.  In your case, I think it really is a stuck air valve in the rear.  At least that's my laymans view.  I don't envy the job of crawling under there and fiddling with air lines.  A bus pit sure seems like a good idea, eh?

[Sammy]

Send me the 10th digit of your VIN and the last 4 numbers of your VIN.
I have air schematic diagrams - need this info to check the proper one for your coach.
I'll check the diagram and might be able to help.
You can send the info in an e-mail if you prefer.
I work with a fleet of H3-45's with this same feature.
Sammy 

[jok]

The tenth digit is "L" and the last four are "1606". I appreciate your looking into it. It would be great to have a pit in the barn. But, I guess I'm pretty lucky to have a good concrete floor in the barn. It makes it nice not having to work outside in a state with 4 to 6 months of cold weather.

Maybe you guy's can help with another "air levelling" question. When I lower the front (kneeling) it goes down quick. But, when I manually raise the front it is very slow. It seems slower than raising the rear one side at a time. Is there an adjustment to increase the amount of air going into the bags? Thanks, jok

[jok]

Sammy,

Thanks for checking into my level problem. I was hoping to work on it this weekend but it didn't work out. Maybe next weekend. I tried returning your e-mail, but I changed my e-mail address and am having some problems.

I noticed the street rod in your profile picture. Have you ever been to the NSRA Street Rod Nationals North? They are held each year in our home town. It is great to look at all the great cars.

Anyway, thanks again,

jok

[Sammy]

John, I've never been to the NSRA event near you. I'm sure it would be a great time.
I recently sold the car, now looking for my next project.
I don't own a coach, just work on 'em for a living.
I don't claim to know everything, just enjoy helping when possible.
Best of luck with your repair.
Sammy

[darrenayres]

Hey JOK. What advice did Sammy give you?