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Urgent Help needed, ride height issue
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I assumed that because all other functions of Level Low worked and that it eventually maintains air once up and going down the road that the PR2 was a good culprit. Mine looks sorry anyway and they’re cheap, so it’s no harm done, particularly as I’ve got a mysterious loss of brake air in less than 24 hours that is a somewhat recent development. Also going to change the check valve below the manifold that feeds it, another cheap part, “as long as I’m in there”.
This bus hasn’t seen much air system maintenance and I’m still getting it caught up.
My crack tech down at the bus barn recalled a scenario where Liberty replaced everything – Norgrens, filters, the works – for a local Liberty owner some years ago and at a rather hefty cost. Same problem thereafter which she solved with the same solution (PR2); in that case, they inexplicably hooked the PR2 up backwards. As an old teacher of mine once said “that took talent”.
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Been following this post closely, I am having similar issue. Had Prevost install new airbags in the front some months ago & coach has never seamed to get any higher than ride height. Thought perhaps wrong bags were installed. Prevost put another (new) set of airbags in the front on Monday, but bus still doesn’t go above ride height. Prevost replaced the PR2 valve and the filter screen in the aux air filter in the front drivers compartment. Still not going above ride height with the 125 PSI in the bus system. Prevost then connected their shop air (160 PSI) to the front aux air fill. Presto bus went up above ride height quickly and smoothly. Removed shop air, increased engine air governor to 135 PSI, bus wouldn’t rise above ride height. 160 PSI shop air reconnected to front aux fill and coach rose above ride height no problem.
Apparently there is a sticking valve in the front system that can be over come by the high shop PSI but not by the bus compressor air set at 135 PSI. Any thoughts as to which valve might be the culprit?
Chuck
P.S. My bus also will come just short of ride height after sitting for awhile and only achieve full ride height after driven.
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Brake air and air for the suspension are two unrelated systems and a loss of air on one of them has nothing to do with the other.
As to a sticking valve in the suspension, it is important to understand how the level low Norgren valves work. If you lower the coach using manual control of the leveling system, and then use the manual control to raise the bus, if the bus goes up it means there is no valve sticking. Period. A spool valve, which is what the Norgrens are, open and close off air flow by sliding a spool sideways in a bore in the valve body. To move the spool air pressure from the solenoid valves in the 5 valve manifold push the spool sideways and either spring pressure returns the spool or pneumatic pressure from the other end of the spool returns it. Increasing system pressure increases the force pushing the spool sideways, but if the coach goes up to driving height it is established the spool is moving and the valve is opening, and additional pressure will not change anything. If with the coach air system it will not rise above the driving height, but it will go beyond that with shop air then the air bags are being forced to extend well beyond their design limits.
Air bags are marked to indicate pressures should not exceed 100 PSI. Going to 125 to raise manually is likely OK because the air bags are not going to see any pressure greater than that. Going down the highway as the bus hits bumps the air bags compress and internal pressures go up which is probably why pressures are limited to 100. I know from my coach with the front axle weight at the maximum allowed weight it takes about 100 PSI to reach the driving height, but greater pressure up to the limits of the system will bring the coach another 3 or 4″ up.
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The PR2 valve referenced above feeds air to the height valve. Mine was very corroded internally and was worth changing along with the check valve below it just as a preventative measure. The old one was also not fully threaded into the junction block which was also an air leak, no clue how long that had been like that.
In my case, the middle of 5 Norgren solenoids was also shot, this is the only 24V one in the stack on my Liberty Classic (steering bay, back wall, door edge). Replaced as well this afternoon and now working as it should. I would like to change the other 4 12V solenoids as a preventative measure if someone has the PN for that part.
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That manifold we call the “five stack”. It has 5 “coils” and a “armature” under each coil. The following applies to my Liberty “Classic”
#1 = 12v coil is for supply
#2 = 12v coil is for manually raising & lowering front
#3 = 24v coil is for the normal D”drive” mode
#4 = 12v coil is for manually raising and lowering the back right
#5 = 12v coil is for manually raising and lowering the back left
12v coil = pt# 54452-02 = $25ea – https://www.imi-precision.com/us/en/
24v coil = pt# 54452-03 = $17ea – https://www.imi-precision.com/us/enUnder each coil is an “armature”, pt# 54462-31, $36 ea https://www.imi-precision.com/us/en
2000 Featherlite H3-45
2024 Jeep Grand Cherokee
Leesburg, FL -
Thank you, Don! Priceless!
Looks like the connector I needed is 54934-01 – got this from someone stocking Prevost parts here in town. I am stocking up to redo the other 4 plus all 5 “armatures” thanks to you.
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Jon:
If I understand correctly what your saying is – If the front airbags raise to ride height (and they do) the valves are working and the added high shop pressure is just pushing the bags beyond their limit. Sooooo that brings me full circle back to the problem is incorrect airbags were installed.
Chuck
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Don, not all coaches have 12V solenoids in their manifold. In fact I think Liberty might be the only one on Classic models.
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Chuck, here is my thinking, but keep in mind it is based on a system that doesn’t act strange due to abnormal conditions such as hydraulic lock from water or inhibited valve operation such as from sludge created by moisture in the system or valves.
Your coach will only go above or under the driving height in the manual mode. To verify the valving that controls raising the coach above the driving height is working lower the coach. Then command the coach to raise. What you are doing is asking the needed valves to function in such a way as to open the path from the accessory air tank to the air bags.
If the coach rises at the location (in this case the front axle) that path for air flow to the air bags is open. The only unknown is if the valve is fully open but that has nothing to do with how high the coach will rise. All a partially open valve will do is impact how long it takes for the air to enter the air bags.
But you said your coach will not rise above the driving height nor did you state it takes a long time to get there so if the valve is not fully open that does not appear to be the real problem.
Whether you have the correct air bags is something to be determined. If prior to the change in air bags you were able to fully raise the coach at the front axle, and since the change you are not that strongly suggests air bags could be the reason.
I will tell you that when I started raising the issue of coaches being fitted with the wrong replacement air bags a long time ago the push back I got from Prevost was substantial. I pissed off a lot of folks there and it came to a head at a POG rally in Oklahoma City when two Prevost managers realized the 630259 and 630260 part numbers had been switched or reversed and that was why coaches were not coming all the way up as designed.
I have no idea what your particular air bag part numbers should be but if the coach worked previously you should have it work correctly now. But be prepared to stand your ground and push hard to get it fixed. I have given up trying to get the system to list correct part numbers because there was a similar situation with flex hoses in the turbo to CAC system in which hot rated hoses were called for on the cold side and cold rated hoses were called for on the hot side. Boater Al got involved in that and that was another battle to get resolved.
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That’s why this info is so valuable as Prevost does not carry the 12V solenoid. Lots of us with Liberty XLs that are not Elegant!
Kelli was telling me about a local guy who was having trouble with his suspension some years ago and dropped it with Liberty in FL to fix it. They charged him somewhere well north of $30k and replaced all Norgren components, not sure what else they did. They gave it back to him with a couple lines reversed and it worked worse than before. She figured it out and got him sorted. Yowza.
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When you put it on ride mode center solenoid supplies air to the#14 port control side of the 5 port norgren in steer compartment that opens ports #2 & #3 that’s gets aux air via level valves that puts coach into travel mode, on mine rear comes 1st then front comes 2nd and it comes up slower till level valves are satisfied. In level mode to lift or lower front solenoid #1 & #2 have air to 3 port and 5 port in steer are used air to #12 control port on norgren 5 port opens ports #1 & #2 and supply air from sol #1 opens 3 port which puts air or removes air from front bags. pretty simple, if there is 90 to 100 lbs in aux tank front should lift easy. If not I think front bags are to short, 160 lbs are way over extending bags. yours is heaver then mine, and mine will go way above travel mode now! but before, Thanks to Don Beard I bought the correct bags before it would not lift much higher then ride height. Old bags and new bags same diameter but new is taller.
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Chip, who is stocking Prevost parts in Augusta?
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Upon Gil’s suggestion I raised the tag axle then attempted to raise the front above ride height with level low. It came right up (about a minute or less). Left front locked/raised with level low and lowered tags. Front stayed locked above ride height as it should have.
Lowered coach completely with level low then turned level low off. Coach rose to ride height in about 3 min in high idle.
I assume that means all valves are working correctly, fronts just to heavy to get above ride height. Front axle weights 17’700 LBS. total coach weight 7/8 fuel 3/4 water is 54,450Chuck
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TJ’s has some on the shelf (basics) but Lewis has more.
Nice to know another nearby owner.
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Andre:
Sorry, didn’t mean to Hi Jack your post. Did wait until you resolved your issue. Seams to be a similar issue.
Chuck
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