[Archived]

It looks like someone has been under that bus messing with things, I see only one bolt holding the valves in place. Unless you bought this bus “as is” i would call the seller and ask what’s up.

[Archived]

I believe Greg has nailed it.

There is a guy on another forum that everyone idolizes but over the years he has gotten creative and has not been afraid to modify someone’s coach. While that may be OK as long as the coach owner knows exactly what changes are being made and it is documented so the next owner or mechanic has an understanding of what was done, that really can be a can of worms for the next guy that needs to work on a coach. I am not saying he did this, but whoever has been maintaining the coach did not fully appreciate how the system needs to function.

First, I hope you are not getting under the coach without it being supported under the chassis support points. ESPECIALLY IF YOU ARE WORKING ON THE SUSPENSION OR HAVE ISSUES WITH THE SUSPENSION.

Now back to the issue. Go to this site, pull up your coach specific pneumatic diagram and get it blown up at Kinkos or somewhere so you can easily read it. http://prevostparts.volvo.com/technicalpublications/en/wiring.asp

I suspect the Norgren valve shown is up on the frame between the drive and tag axles. If so that valve is normally an open path between the drive axle air bags and tag axle air bag. When the coach suspension switch is in the “road” position all three air bags per side are inflated. The only time that valve closes is when you lift the tag axle, at which point it exhausts air from the tag air bag while shutting off the flow of air from the drive axle air bags.

If your tag air bags are not inflated it is usually because the valve is closed and air from the tag has been exhausted. In your case someone likely screwed with the suspension system and plugged the exhaust, and it is possible the valve has not opened to allow air into the bag. That could be a result of other changes to the system or the switch in the wrong place at the dash or a pneumatic system that has had that valve and others damaged by moisture and not functioning.

Your axle weights are what would be expected. They were likely taken when the air bags were all inflated.

I am not sure the above is accurate advice because not enough is known based on your description. First the system needs to be compared to the pneumatic diagram and restored, and then it needs to be operated through all positions to determine if in fact there is an issue.

If you are near Liberty in Stuart or Jeff Rowe in Vonore TN you need to get the coach to them so it can be inspected and possibly be repaired. If the system has been damaged by moisture and then someone who was inexperienced screwed with it you are in a world of hurt and it needs to be repaired. If you prefer to do your own work that is OK, but before you begin go to the Prevost Car web site and on the commercial side conect to their list of webinars to access the webinar relating to the suspension. Additionally look at the suspension articles on this site in the articles section.

https://prevostevents.webex.com/mw0401l/mywebex/default.do?siteurl=prevostevents

The links above should help you. The best thing is for you to get familiar with all the information available through the Prevost Car site if you opt to do your own work, otherwise the two places I listed above are your best bet for repairs and service.

[Archived]

I have 2 sources of info that says the tag axle wt is too light and drive axle wt is too heavy that I mentioned in my original post here. They are: The data plate on the wall next to the driver, and a sheet that I found in with the Prevost MX and Parts manuals.

Don’t give up on me

[Bryan]

I have they schematics. The mx and parts manuals came w/the coach.

What is this? I’ve provided near and far pics

[Archived]

I need somebody that has a coach like mine to go look and see if their 2 Norgren valves on the inside of the frame rails just aft of the rear differential have pipe plugs in 1, the other, both, or neither. See my picks from my original post here.

Thanks

[Archived]

Easy question first. The two Norgrens you describe should have the bottom port with a 6″ length of plastic open to atmosphere so when you lift the tag the air bags will dump. The plastic is the air drain.

Try to understand those two valves are there as explained previously solely to either maintain an open path for air between the tag and drive axle air bags which is the normal position for them. Only when you lift the tag axle do you need for the valve to shift, shutting off air from the drive axle air bags, while opening the path from the tag axle air bag to the exhaust. You cannot lift the tag axle unless the air bags are empty of air otherwise you are lifting against the air bag pressure.

I no longer have my pneumatic diagram for my 96 shell coach so I can’t tell you what that is you are pointing at. I would need to follow the air lines to and from the device to understand what is being shown The fact you have the pneumatic diagram is going to be a great help. Use different color highlighters to follow the air and you will begin to understand more about how the suspension logic works.

What is important to realize is that the 3 five port Norgren valves on your coach determine if the suspension is getting (or exhausting air) from the ride height valves as it does when in the road position, or if the five port valve has shifted to allow air to or from the three port valves that control filling or emptying the air bags. When the key is off the five port Norgren valves go to the normal position which is to block off any air from entering or escaping the air bags.

As to your tag axle weights, they are exactly within the range I would expect. The weights shown on the data plate are gross weights.

We’ll hang there with you.

[Archived]

If it seems like you are being given information in bits and pieces it is because the suspension systems are complex and it is only difficult to understand if you don’t understand the underlying principles. The post above should help you answer some of your questions you made when you started the thread.

[Clifford]

I agree, your tag is light. I would guess the one tag bag was deflated when weighed. Your tag weight is clearly outside the nominal, not even the higher loaded, value on the placard. As a result, your drive is over weight. For the longest time DoT limited drive axle weight to 20,000. In recent years it has been increased to 22,000 or 22,500 (I can’t remember which). Although we aren’t subject to the commercial DoT rules, I point these numbers out to show your drive exceeds both Prevost’s limit and commercial limits.

Once you fix the tag, check your weights again.

[Archived]

Duh……..Gil is right. MY brain (what’s left) isn’t working. I was seeing tag instead of steer.

You ain’t going to let me live this down are you Gil?

FWIW If you bypass the two three port Norgrens that have been plugged just temporarily and join the air line from the tag air bags to the corresponding drive axle air bags you will get the proper inflation of the tag air bags because under normal conditions when the valves are working as intended the drives and tags are all the same pressure and that is determined by the ride height valves ahead of the drive tires.

It is a guess but the three port Norgrens between the tag and drive axles are frozen up and not allowing air to flow and the plugs are keeping air from exhausting. You don’t need to lift the tag axle except under certain limited conditions so you could actually drive the bus without repairing or replacing them for now.

I gotta go and take my meds.

[Sammy]

do your tag lift bags inflate when you throw the lever? Look at the supply and control lines on the tag lift norgren __Jon? shared with exhaust of tag(control) of tag air bag? It will be tomorrow before I can check mine out. Bob Hard to tell from pictures–just a observation..

[Jerry]

Thanks Everyone!

No the tag actuators don’t budge when selected and there no exhaust sound either.

Here’s a couple of questions for yawl?

1) Does the aux air system have anything to do with controlling the tag bags?

2) the valve pictured below(Norgren#??????), which is connected to and just aft of the driver side Norgren bag valve, has a pipe plug in it too? I don’t think it is suppose to? I believe where the plug is the exhaust for the tag bag actuator chambers? The Norgren #K910026 are $1.70 ea at finditparts.com.

Thoughts?

I bet-cha there was a normally closed tag bag valve(#K910026) or two stuck open so the exhaust ports where plugged to get down the road or out the door? I’m gonna unplug them and see how everything works(or not).

[Archived]

You have to think of your suspension as three separate systems, a front, a LH rear and a RH rear. Doing that starts to simplify its operation in your mind.

Since you have issues with the tag here is how that is supposed to operate. The 5 port Norgren ahead of the forward fender liner in the rear is the “gateway”. When it is closed (the key is off) the internal spool goes to the normal position and air cannot go in either direction to or from the air bags. Whatever position the air bags are in is where they stay when you turn off the key.

In your Liberty, if the suspension selector switch is in the “road” position and you turn on the key, the ride height valve determines if air is to enter the air bags or be exhausted from them. The three port Norgren between the axles at that point is just an open path and contributes nothing to the suspension operation.

The ride height valve admits or exhausts air as necessary to maintain the height above the ground for driving. It tries to maintain about 11″ between the top and bottom air bag mounting plates.

If you switch from the road position to the auto or manual position the 5 port Norgren valve shifts the spool in the opposite direction to allow control of air entering or leaving the air bags either manually by selecting the up or down position on the appropriate switch or automatically. That switching is done in the 5 solenoid valve stack by opening or closing solenoid valves which in turn open or close the appropriate Norgren 3 port valve to admit air or exhaust air.

The only time the 3 port Norgren between the axles comes into play is when you move the tag lift valve at the driver’s left. Don’t consider that valve part of the suspension system because it is only there to control the 3 port between the axles to shut off air flow between the driver and tag air bags and exhaust tag air bag air. The tag lifting devices are nothing more than #36 brake chambers and when air goes to the 3 port Norgren between the axles it also is sent to the tag axle lift chambers. The air sent to the 3 port does nothing more than shift the spool between its normal position maintaining an open path to the closed position blocking air from the drive air bags and dumping air from the tag.

There it is. The entire operating theory in a few paragraphs.

If your tag doesn’t lift for now, forget about it. First think about getting the system restored to its original condition. Now would be a good time to post the name of the “mechanic” to warn others the village idiot is on the loose so no one else gets screwed by this guy.

Once you get the system working then you will find the air bags inflate and when you lift the tag you will hear air escaping. If the tag doesn’t lift it could be a bad brake chamber or other issues with the valve(s) that control the tag lift. I strongly suspect you are going to find issues through the system possibly water damage that is going to have you REPLACING all Norgrens. I stressed that because once water gets into them and the mirror polished surface corrodes it is a waste of time and effort to replace the spool of O rings because they are going to leak and the coahc will lean.

So here is the simple answer. The aux air system is just the source of air for the suspensions.

Your pneumatic diagram is valuable to you in that whatever was screwed up in the past can be undone because Prevost did a great job at representing the fittings that belong on each valve including the orientation of the fittings. But you still have a lot of detective work to do to unravel what has been messed up.

[Archived]

Jon has it–things have been changed. the (small) black is a signal just like turning on a electrical switch. the blue is a supply when traveling from the leveling valve located in front of the duals each side rear=supplys all three air bags on that side–two on drive and one on tag—- the norgren switches the one off on the tag when you want to lift it. other wise it recieves the same amount of air as the two on the drives. Things have been disturbed back there. The tags call for a differant air bag size than the two on the drive axle. I just rebuilt all my 98 45xle suspension. Just be patient and follow the diagram specific to your bus. They are common but change from unit to unit to unit on minor details( mostly in front norgren ) cinfrig. Just remember if you put air in a bag to colapse it you must let it out. I know that sounds basic– no disrespect intended. Look on the back side of the blank valve(face )and see if it is marked with flow direction/normal open-closed. hope this helps. Bob

[Corey]

We bought the coach, S-5665, from Parliment last Jan. We were told it was a 2 owner coach since new. The original owner had it for 16 yrs, then the owner of Parliment bought it for his personal coach and had it for about a yr. Then we bought it. They told us they did a PDI. I now know what they call a PDI and what I call a PDI are two different things. I’m disappointed, but not surprised. We live in the San Antonio TX area and they are in FL so we’re SOL. Will I buy anotherPrevost? Someday, yes! Will I buy it from Parliment?

Currently, I have the pneumatic system working well in the travel and manual leveling modes. I’ve set all airbag heights at 11 1/4″. I haven’t tried the auto leveling mode because I prefer to do it manually. What doesn’t work is the tag raise feature. I believe it doesn’t work for multiple reasons. I think there is a hole in the drivers side actuator camber. And the tag bags don’t dump because the exhaust ports in the 3 way Norgren valves have pipe plugs in them. If I pull the plugs out, I loose the air in the tag bags when they are suppose to stay full. The question is: are the 2 rear Norgren valves malfuctioning, or are they the incorrect part#?

The paper schematic(D140202-rev D) that came in the mx manual with the coach, and the 2 the PrevostCar website that applies to our ser#,(D14202 rev E, & D140211) are NOT what is installed on our coach. The schematic that looks more like our coach is D140212(minus the ABS) because our coach has two 5 way valves, #s 166 & 167, and the 5 solenoid shuttle manifold. The system depicted in schematic D140212 is for a later ser#?.

Question??????????????? Do the schematics depicted on the PrevostCar website reflect any and all changed the converter has made?

I plan to call Liberty Monday to ask them. Then I’ll have a better idea of what is right and wrong with our coach.

Thanks!!!!!!!

[Archived]

From everything you have said it is clear someone has monkeyed with your suspension.

I said previously to forget the lifting of the tag axle because while you are hung up on that feature you are ignoring a very easy temporary fix.

From the “T” on the rear drive axle air bags connect directly to the fitting on top of the tag axle air bag.

That does two things immediately. First it restores the tag axle bags to become an integral part of the suspension system. Unless someone really screwed up your coach your suspensions will work as intended in every respect except allow you to raise the tag. You should be able to manually raise and lower the LH and RH rears as well as lower or raise the front. The suspension should work perfect in the road position.

Second it will enable you to learn if anything else is screwed up if it will not do all it is supposed to.

Don’t do that change however if you have no way to block the coach up under the chassis support points. If you do no want to do the work yourself get a mechanic to do it, but do not let him do any more than I described above. The minute you loosen the fittings you will exhaust air from the rear suspensions so the chassis MUST be blocked up.