Level Low Question

[ppranschke]

Hi,

We are new Prevost owners and would like to know what the standard operating characteristics are of the level low system (98 XL).

Specifically, should I be able to raise the front of the bus from standard ride height without having to lower both sides of the rear.

Any help would be appreciated.

Thanks

[Pete]

Yes, you should be able to raise the front of the coach without adjustment to the rear. Are you unable to raise it? Prevost did ship the incorrect bags for the front of the coach for a period of time. Joe Camper can provide further info on this issue if that is the case.
The front of the coach will only go up or down. Any lateral (side to side up or down) must be done by the rear bags of the coach.
Peter, I am not sure this answers your questions or not, and if not maybe others will chime in, or you might want to ask more specific questions, and I am sure POG members will be able to answer them.

Welcome to the world of Prevost Ownership!

[rahangman]

Joe Camper is the Go TO Guy for help...and more. Dreamchaser is another excellent source.

[n33d2camp]

zzzzzzzzzzzzzzzzzzzzzzz

[Joe Camper]

Il try try to explain what I have learned and give some opinion and some easy and inexpensive things to deal with buses with heavier front ends. these buses do not have the ability to raise the front axle above ride height or also having very slow response and performance in level-low.. When U R at the controls bus in high idle with your finger on the up button and all has come to a stop the front end either has stopped going up or it seems never even started up and above normal height in the front. Take your finger off the up button. Pump the brake pedal and get the air pressure down to 90 or so and get the air compressor on the engine pumping. When U see the needles to begin going north of 110 psi but before U get to 120 or 125 where the compressor stops THEN push the up button. SOMETIMES if the front is only slightly heavier than components under normal opporation of levellow could raise it, it will go up trying this method. If the air pressure seems to be getting close to the cutoff before the front gets high enough take the bus out of high idle so the compressor does not stop pumping air before the targeted front height is achieved. Otherwise as soon as the compressor stops pumping the front will stop going up. If this occurs repeat the process again. Because the suspension air is coming from the auxilury tank and the pressure regulator is tapped into the brake tanks often a situation is created where U have your finger on the button the aux air pressure is at 90 but because the brake tanks R still at 120 the regulator will not signal the compressor and the aux air at 90psi will not elevate the front end. If this doesn't bear fruit the solution is to raise the cutout for the compressor to 125 or 130psi.

[Joe Camper]

The newer buses with the aux air gauges in the dash U can see this going on when U R on the up button in level-low. If the air compressor is idling not pumping when U first try the aux tank needle drops well below where the brake tank pressures are. If the brake tank pressures aren't dragged below 100psi where the cmpressor kicks in (and this is exactly what is occurring at this point) U can lay on that up button till hell freezes over and nothing will happen. If U pump down the brake tank pressure get the compressor going and try up when the needles are at 110psi and headed north NOW the difference in the 2 systems is just a slight bit. I am going to tap a pressure gauge into the front bags on a double slide bus one of theses days. What kind of pressure are we dealing with at ride height and what additional pressure from there to go up. IMO and based on what many here experience I think it is just a bit too close t 120psi and as few as 3 or 4 PSI increase in the shut off very often eliminates the shortcoming.

[n33d2camp]

zzzzzzzzzzzzzzzz

[Joe Camper]

Let me pass on a repair I did for Pam and Loyde a couple who were some of the first POGers for U newer members. We were at Eric and Debbies and using their barn and pit. We had just replaced front bags. As I was checking ride height I discovered that the arm on the ride height valve was not 90 degree to the housing of the valve and that means it is still too low. We were baffled as the newer 259 bags were the ones we were using. Loyde also mentioned he was aware of that condition and added after driving for an hr or 2 when pulled over it is noticeably higher and what looked like correct???? WIERD. So as I was in the pit under the front end with the bus running actually in the process of measuring heights with a tape I noticed the dern thing just start to begin to come up move maybe 1/4 inch and right then as it barley moved the air dryer sneezed the compressor stopped and the movement up stopped. It was immidiatly evident to me what was going on. Like Loyde mentioned first start in the morn the front sits low but after on the road and about 50 cycles of the air compressor under normal opporation each time the front comes up another 1/4 inch until finally getting there. Turned up the air pressure 5psi end of problem. This is what lends me to believe that the threashold of pressure needed to raise the heavier front ends is just a tad too close to the standard 120psi most things opporate wonderfully at.

[Joe Camper]

Even U guys and girls with automatic leveling. Want max performance? Say U r at a spot the front needs up. Get the compressor to cycle on or better yet right as U pull in and stop its usually working at this point. Set the brakes turn on the high idle but watch the air pressures and turn off high idle when U get to 100+psi before turning on the auto level. If U don't what will happen is it will get to pressure and cut off often before the leveling is finished and if its not done yet and U r on a slope done in front it may or may not make it. Try it U will like it. In either event the system will preform better.

[Joe Camper]

Not all buses are the same some if older or a bit weaker compressor U can actually let the pressures climb all the way to 115psi before turning off the high idle and the leveling will finish before the bus gets to 120 and the compressor stops pumping. Other newer buses or with better compressors U cant start that high and the compressor stops before leveling is finished. Once U do it this way a few times U will get a feel for just how yours likes it. And U will see the bus smiling I promise.

[Joe Camper]

AND if after all this fails THEN U have to raise the regulator upping the air pressure a bit. Test and first watch it very close at see if the same thing is occouring as we found on Loydes bus. Get out a tape and measure thru pumping the brake causing repeated compressor cycles on high idle measure at the bottom of the first bay door at the back of the steer tire to the ground. U will begin to see just a very slight movement up and swoosh the dryer sneezes and it stops. Repeated cycles produce similar results till ride height is achieved. If U take it out of high idle often ride height will go more between cycles if not get there right off. Again if all else fails its the stinking air pressure and U could not ask for an easier fix.

[ppranschke]

Joe,

I will give this a try on the weekend. Thanks for your phone call.

Cheers

Peter

[Joe Camper]

In the big scope of things its really not a big factor. Normally we are on flat spots or we are wanting the front down not up. The thing is when folks actually try to go up in the front and things don't happen you tend to get worried a bit. Now U know what is happening. Although we all have similar suspensions they are all different to. Im completely confident many who read this do not have poorly preforming level-low. We are all different. They were in a constant state of evolution. The bags then the fitting sizes then the size of the lines then the additional tanks for the bags. I have experienced the entire gammit of performance in level-low from bus to bus. Another thing to consider is this. Comparitivly , to say, the trucking industry our front ends are heavy way heavy. Even tho the max weight for a straight truck of 3 axles is the same weight limit as for us 54000lb I can tell U most 3 axle straight trucks do not have the ability to put the 20000 on the steer in order to get the max of 54 without going over 34000 on the rears and subsequently the gross is significantly less be lucky to see 14000 on the steer on a 3 axle dump for example. Most road trucks are 10,000 on the steer only sometime approaching 12,000 very rarely. The wheelbase on the bus makes it easier to load the steers Most of our stuff is north of 15000 and the newer heavier buses are aproaching 54000 the legal limit and that means there is very close to 20000 on the steer axles to remain legal at those weights. This is the nature of the animal we are talking about. If we have to go thru some contortions on some of the heavier front ends every now and then on some rare situations so what. Usually we are still the nicest campers in the place.

[ppranschke]

Thanks to all for your input. I got things working on the weekend. I believe I was impatient the first few times I was playing with the system.

Cheers

Peter