Level low fun

[Devin W]

Put my new batteries in today and let's just say I hope I'm either too old or too rich to do that job again myself. Sheer genius the way Liberty utilized the space by hiding the batteries in a spot that tucked away... good fun to maneuver a 160lb battery...

Anyway, the real issue for this post is that I just replaced this manifold:
http://i186.photobucket.com/albums/x150/cs427fanatic/Prevost%20Liberty%20Coach/df5438eb.jpg

Located where #4 is shown in this parts breakdown - it's the manifold in the lower left of the drawing and physically located in the steer bay under the driver's seat (described as Valve, 3-2way 2-Position):
http://i186.photobucket.com/albums/x150/cs427fanatic/Prevost%20Liberty%20Coach/levellowpg1630-000001.jpg

The original issue was that the spool must have been stuck because air would continually exhaust through the port lableled "3". I removed the manifold and took it apart and found some moisture. A was unable to locate a rebuild kit so I bought a replacement manifold from Prevost.

Upon installing the new manifold I fired the bus up to check for leaks and prior to doing anything I found that the air was exhausting from the same port. I cycled the front suspension in the manual setting, first dropping all the way down, then I ran it to the highest setting and then back down to normal ride height. After doing this I no longer had a problem with air exhausting through port 3. In fact, I now have nearly the opposite problem. In manual mode, if I put the switch in the down position the suspension raises. With the switch in the up position the suspension raises. When I take it out of manual and put it to ride, the front slowly lowers to ride height, but doesn't lower quickly like it used too (and how the rears still do). Another interesting thing I found was that after replacing the batteries (I actually did the manifold first), I powered the electrical system back up and flipped the aux air compressor on and the front suspension raised.

To me the symptoms appear that either the new manifold is stuck to where it will only let air out (although slowly) from the front airbags if I'm in the ride position with the ignition on. If the ignition is off or the level low is set to manual the suspension will only raise.

That being said, the manifold is brand new so the odds are great that the fault may lie somewhere else, but where?

Thanks in advance for any ideas -- we're trying to get on the road Thursday AM, and technically, I think I would be fine as when the ignition is on and the level low is in ride it seems to maintain the proper stance, but I'd sure like to figure out what's up before we leave.

[Jon Wehrenberg]

That is the three port Norgren that I believe exhausts air for the front only on a Liberty. On other than Liberty systems that valve is used ot exhaust air from all three suspension positions.

I have stressed before that maintenance of the air system on the buses is very important because once moisture enters the system all sorts of things can happen that defy logic. That valve is supposed to exhaust the air to lower the front of the coach when in manual or automatic mode. When in the road position the front can lower via air exhausting from the ride height valve.

This valve is controlled by one of the solenoid valves in the stack on the rear wall of the steer compartment. I don't know if you have a five or four valve solenoid manifold so I won't guess which solenoid valve controls the 3 port Norgren.

Something is definitely wrong, and assuming nobody messed with the air lines and that you reinstalled them in the same place as they were the air should exhaust when you command the coach front to go down. If it goes up regardless of whether you command up or down something is not working properly and the only solution in my opinion is to start the diagnosis process by making sure your auxiliary air system (actually the entire air system) is dry and all valves function as intended. Allowing moisture to enter the system may just have become your worst nightmare because if it is in the valve you replaced it could also be screwing up a lot of the other valves. Normal diagnosis in an otherwise properly working system would suggest an issue with the Liberty controls, but the minute I read of water found in the system I would no longer consider that as my first guess.

As long as you can operate properly in the road position (for all non-Liberty owners that is the driving position that disables the level low) you are good to go as far as travel.

To diagnose the system in my opinion I would first verify that as you give the system the manual commands, up and down on each section, front, left rear and right rear that each of the solenoids operates. The next step is to then verify that the appropriate 5 port Norgren for each section responds, and then finally the three port valves function when the down command is given. It is going to take time and may require removal and bench testing (or replacement) of every Norgren valve, but initially all efforts can be focussed on the Norgen valves and solenoids that are dedicated to the front suspension only since that is the area of the problem.

I believe the front suspension on your coach has the five and three port valves shown in the drawing and an additional 3 port Norgren at the top above the axle. I'm guessing another Norgren is screwed up and the reason it functions properly is when in the road position the Norgrens are out of the system except the 5 port which directs air through the ride height valve located above the steer axle.

[truk4u]

I would think that you probably have a problem with the 5 port norgren. I don't remember which one of the 5 port valves is the front end, the middle one is ride height. If you can identify the valve, you can swap out the valve and see if that takes care of the problem. Once nice thing about your 94, is you can work the buttons through the window while working on the 5 port.

Jon posted before I was done typing...

[Jon Wehrenberg]

Tom's comment about the middle solenoid valve in the stack controlling the ride height is correct if you have a five valve manifold.

[Jon Wehrenberg]

This is general information, not specific to Devin's issue.

Our suspension systems (there are actually three: front, left rear, and right rear) operate from our auxiliary (or accessory) air system. The Aux air system can be supplied with compressed air from the engine driven compressor or from air supplied by the auxiliary air compressor. Regardless of how air is supplied, moisture is introduced into the air systems as well as some oil. Neither air nor oil are good for the various components that use that compressed air so maintenance to keep that from entering the components is important.

The engine driven compressor passes its air output through a "wet" tank and a large air dryer. Auxiliary air compressors may or may not pass air through a dryer or a moisture trap. Therefore is is important to periodically service the tanks, traps and dryers. The tanks and traps should be drained routinely. The dryer elements should be replaced according to the recommendations.

But what if this routine maintenance is not performed? The most obvious result is potential corrosion of the various valves and devices in the air systems. More extreme problems could be a hydraulic lock such as when water enters components and prevents the component from functioning because unlike air, water cannot be compressed. Moisture in the systems can also freeze. There is nothing good about a system with moisture in it.

The more likely impact of moisture is internal corrosion. Our suspension systems rely on dry compressed air. The aluminum valve bodies have a highly polished interior. That interior contains a spool with multiple O rings that slides back and forth to open or close air paths within the valve. The O rings are coated with a liberal application of lubricant that I presume protects against corrosion and allows the spool to slide freely within the valve body. If moisture does get inside the valve body corrosion can occur. The first impact of corrosion within the valve body is likely to be leakage past the O ring creating issues such as the leans. But as corrosion worsens it may create enough drag to affect the ability of the spool to move freely within the valve body. The spools within the Norgren valves are pneumatically actuated and spring return. Or they may be actuated in each direction via pneumatic operators at each end of the valve body. Regardless of how they are activated, they are not designed to overcome a hydraulic lock from water, or excessive drag due to corrosion.

These parts will provide excellent long term service if they are routinely exercised and the systems are kept moisture free. But if not, you can imagine the results. My intent is not to scare anyone, but to help everyone understand that in maintaining our coaches the devil is in the details. Air system maintenance is not limited to a pre-trip brake check or making sure our gauges go to 125 PSI. It includes drainiing all tanks and moisture traps at regular intervals (I do mine every 5000 miles) and replacing the air dryer cartidges routinely. I do my replacement every two years.

Despite routine maintenance the valves in our suspension systems do slowly begin to fail, meaning minute leaks due to wear and age become more severe. Even in a perfectly dry system at some point these valves should be replaced or rebuilt. I have struggled with leaks and leans over the years with both my coaches, and I know once I start to get the leans I have to decide to chase the problem or start replacing all the valves. After chasing problems one valve or leak at a time I have reached the point that my Norgren valves in the suspension systems will be replaced at 10 years of age. That was an arbitrary number, but it seems to me to be a good compromise. I know from experience that they will need replacement and I also know problems show up first in cold temperatures. By rebuilding or replacing all valves every ten years I have a lot of years with no issues or leans. Along with air bags which I also replace at 10 year intervals I have a cost of less than $2000 for parts every ten years. I justify that by saying it costs me $200 or less to maintain my air system each year including the cost of air dryer cartridges. If you do not do your own work your cost may be $400 per year but compared to depreciation and other true costs of ownership that maintenance is a bargain.

So part of my air system maintenance is a timely replacement of all valves and air bags. Owning a bus ain't for the weak of heart, but when everything is working right nothing beats owning one.

[Devin W]

Thanks, guys. I'll play with that info to start with.

[Devin W]

I'm not sure that I would call it a complete repair yet, but I have everything working. It was interesting chasing the problems around.

I started with the manifold that I had just installed as: 1) it was the only different piece in the system since the change in symptoms 2) as I mentioned there was some localized moisture on the manifold that I replaced. I removed the manifold and disassembled it. There was no moisture inside, all o-rings looked good, and the spool moved easily.

With that manifold out I removed the one above it (I think it's the ride control) and did the same thing. There was no moisture in it, but there was some contamination and one of the spool o-rings was missing an edge. Just to get things working I removed an o-ring from the spool off of the manifold that was replaced, cleaned things up, re-lubed with an air-system specific grease and reassembled. I then re-fit both manifolds and pressurized the system.

At that point the operation was the same -- in manual mode the front would only go up with the switch in the up and down position and it would return to ride height with the road position selected. The one difference is that the middle solenoid (3rd one down) on the norgren stack was hissing. I checked my schematic and that one is indicated as the front suspension. I decided to open that up to take a look and right away noticed that it as warm. I took the post apart and confirmed that the spring and magnet inside was moving freely and re-assembled. At this point, I also checked the switch by swapping with the next one over (my leveling has no knobs just 3 position switches) and the operation did not change.

Re-pressurized and this time I had air leaking from the top solenoid in the stack and the system would not operate with any combination of switches. The top solenoid is indicated as the "drive", which I take as road (?) solenoid, so, I took it apart, cleaned the post, disassembled the post and confirmed that everything was moving well and reassembled.

Re-pressurized again and the leak moved to the second solenoid down in the stack, indicated as "air supply". I did not check the system for operation this time and instead decided to chase the leak. I repeated the above procedure with that solenoid.

Re-pressurized again and....no leaks. Cycled the suspension in manual and it exhausted/lowered properly and raised properly, then went to ride height when put into road mode.

So, I did a lot of nothing, but it's working. I'm not sure if something was dirty, jammed, a bit of debris was making its way through the system or what :confused:

It is fixed for the time being and I'll start looking into replacing solenoids or at least having a spare on hand.

There you have it. No words of wisdom, shortcuts, or valuable tutorials there and yet, it's working :rolleyes:

[AprilWhine]

Thanks to all. I am sure that I will need this info before too long, 225,000 miles on our coach. I will sleep better knowing that the valves are serviceable.

Sherry and I made a good living for many years flying out to ships, taking gear apart and putting it back togather. When the CO would ask what we did to fix it, the only answer we could give was, "We put it back togather correctly".

Jim

[Jon Wehrenberg]

Devin,

On your coach with 5 solenoid valves in a stack the center solenoid valve is the "road" or driving solenoid. When your dash switch is in the road position and the key is on, that is the only solenoid valve to open. When that valve opens it shifts the three 5 port Norgren valves to open the air flow path from the auxiliary air system to the ride height valves. With the key off, or with the selector switch to the manual or automatic position that valve closes and the other solenoid valves can come into play taking the ride height valves completely out of the air flow path.

I would urge you to service your air systems to insure they are clean and dry. The mere presence of even a drop of moisture signals ongoing problems if not corrected.

[Devin W]

John,

That's interesting as I have an electrical schematic that labels those solenoids differently, showing driving at the top of the stack. It could be that I'm interpreting them wrong. I'd be the first to admit that I'm learning as I go -- one of the reasons I felt it important to have a membership here. As far as the air system goes, I know that the dryer system is working properly (recently serviced by my mechanic), but when I disassembled the manifold that I replaced I could see where there was an ingress of contamination/moisture over time. Other components that I disassembled showed no evidence of moisture, however, the bowl that is inline on the air system using some kind of desiccant filter (I'm not sure what it's called, but it might be them moisture trap you're referring to) needs to be replaced as it sure appears to have reached its service life. As I mentioned, I'll be watching this closely for any other symptoms and plan to replace a few items to insure the integrity of the system.

[Jon Wehrenberg]

I doubt if Liberty or anybody moved the wiring around on your solenoid valve stack, but you should verify that the center valve is the driving position or the road valve. Since that coil is energized any time you are driving anecdotal evidence from this forum shows it is the one to fail most often. When it fails you cannot get your bus to the driving height, or safely drive it. The short term solution of course is to take any one of the other coils (or valves if the valve has failed) and put the replacement in the center position. That way you can continue driving.

The time for you to figure out which coil and valve is the one for driving is when you are home or at your shop. When you are attempting to leave a campground or somewhere else if the bus will not go to the driving position you want to be able to do a one or two minute repair and get going, not messing around experimenting until you find the valve that controls ride height. My shop manual spells out each valve and its purpose and it calls the center valve as the one for driving.

[dreamchasers]

John,

That's interesting as I have an electrical schematic that labels those solenoids differently, showing driving at the top of the stack. It could be that I'm interpreting them wrong. I'd be the first to admit that I'm learning as I go -- one of the reasons I felt it important to have a membership here. As far as the air system goes, I know that the dryer system is working properly (recently serviced by my mechanic), but when I disassembled the manifold that I replaced I could see where there was an ingress of contamination/moisture over time. Other components that I disassembled showed no evidence of moisture, however, the bowl that is inline on the air system using some kind of desiccant filter (I'm not sure what it's called, but it might be them moisture trap you're referring to) needs to be replaced as it sure appears to have reached its service life. As I mentioned, I'll be watching this closely for any other symptoms and plan to replace a few items to insure the integrity of the system.

Devin,

My coach has a metal bowl, with a woven fiber filter, and a blow down valve connected to the bottom of the metal bowl. This is the place in the air system where air is fed to the aux air system. Humm. The desiccate filter sounds like a good idea, I wonder if the desiccant filter is a Liberty Coach addition.

Sounds like a good idea, I wonder how long the desiccant would last? Does anyone else have this type of set up on their coach?

Devin, also I agree with Jon on the placement of the road ride height solenoid on the "stack". Mine has 5 solenoids and the center is for road position. I have often wondered how many variations of these solenoid stacks are installed in our coaches. Perhaps there is a difference from an XL and an XLV. Well, the important thing is all works well now. Your symptoms sounded like a challenge.

Also, your year model, like mine, has pneumatic logic such that if you have low aux air pressure, the tag axle will release and rear of the coach will settle downward. My coach is 1995 model, I believe this pneumatic logic was changed in the next year model. Their is a modification to resolve this, but it is easier for me to keep the aux air system tight.

Good Luck.
Hector

[Jon Wehrenberg]

Here is the suspension upgrade that changes the level low logic that Hector refers to.

http://api.ning.com/files/iWAEFc41PyR93QmtwRc6HkEM9QrxtsX0uQrBCVXhqSaF7qBOmP Lr-xAH0pLVVfu3J4nesHxVq3MWq2o18WWzsJmOtcRhkZ7I/PUB96ENG1.pdf

[Devin W]

Thanks, guys. Once again, that's great information. Based on what both of you have indicated about the solenoids and the fact that the center solenoid was the one that got hot with the ignition key on and suspension in road position I'm thinking that my electrical schematic is either wrong or there wasn't care given to properly identifying the solenoids in actual sequence.