[Archived]

Go to the articles section on PC and you will see some detailed articles that relate to the level -low system.

Having said that your coach has an issue very likely related to the rear suspension on the low side. It could relate to the 5 port Norgren valve, any of the three air bags, the 3 port Norgren between the tag and drive axles or the fittings themselves.

Since you said this came on suddenly let me ask a question. Did you lift the tag axle just prior to this happening?

As part of the diagnosis put the level low switch in the normal driving position and raise the tag axle. Allow the engine to run on high idle for at least five minutes to get the rear of the bus to raise as close to the normal driving height as possible. Turn the bus off and see if the bus leans as it has been doing. If not the problem is related to the tag axle air bag, fittings, or the 3 port Norgren valve. If it does lean as before the problem relates to the two drive axle air bags, the fittings or the 5 port Norgren.

Free advice……..unless you are prepared to take the time to chase the issue, given the age of the coach you might find it cheaper to replace all the air bags, valves and fittings because age is the biggest problem and once one leak is found and fixed another is likely to pop up. Renewing everything puts those issues behind you.

[Chris]

Sould have mentioned, the pressure in the bus air systems is unimportant. On that vintage coach once the bus is level on a tight suspension all pressures can go to zero and the coach will still not lean.

Air is locked in the suspensions with the key off.

[Archived]

Thanks so much. Headed to the coach now to do the above check. I will follow up.

[Chuck]

Followed the steps above and the bus immediately started to lean to the driver’s side. Bus is now shut off and one tag tire is off the ground the other is touching the ground on the driver’s side.

In addition I have lost about 6 # on the dash gauges if that matters. This is within about 10 minutes of shutting off the bus.

The test worked and she is leaning.

[Ronald]

Your dash gauges, primary and secondary brake, should have no bearing on your suspension issues. If you have an aux gauge, that is what feeds the suspenson.

[Archived]

Is there a way to eliminate the Norgren from the air bags before I start the process?

We have a very well run Big Rig shop (MCH Kenworth Service Center) here in Tulsa that is a full service center. We do not have a true Prevost service center here. My question is: Do any of you allow diesel shops to work on the chassis side of your coach?

I have them do all the engine/lube/maint. etc….. on our bus with great results. They seemed very well versed in air bag replacement on the trucks.

[Archived]

The Prevost Level-Low system is not so complex it cannot be serviced by someone willing to do a proper job of trouble shooting. But having said that non-Prevost mechanic all seem to want to get creative and take shortcuts with the bottom line being a modified coach that nobody can service without starting from scratch.

If your bus leans left or right, or sags down in the front you already know (based on what it is doing) where to look for the problem. If it leans over as fast as described Stevie Wonder should be able to diagnose the specific problem. Soapy water, a stethoscope, or a line set up with a pressure gauge to measure air leakage is essentially all it requires along with some patience.

Soapy water will not reveal a leak in the bottom of an air bag because your cannot see the bottom due to the “piston” the bag rolls over, so if there are no soapy bubbles evident on the system, inflate the bags and see if they hold pressure. If you apply pressure from the air bags back to the 5 port Norgren you will learn if that is your leak source. You can put a plug in the exhaust in the 3 port between the two axles to see if that is leaking. My point is it can be done right or you can let someone that does not have a clue start to screw with your bus and possibly mess it up.

[Archived]

when I replaced my norgren valves earlier this year, I found a 5port where a 3 port should be (between the drive and tag). I dont know who did this but i’d bet it was a truck shop via the prevoius owner.

Just saying ….. i’m doing more and more work myself as time goes on.

[Paul]

Joe points out an issue that has popped up more than once. When anyone on our forum offers advice or answers questions those are usually based on how an unmodified coach is set up. The questioner who has a coach that has been modified then compares the answers to what he sees on his coach and all of a sudden something doesn’t add up. So we then see a back and forth Q&A in which we begin to recognize is a “failure to communicate”.

It is tough trying to diagnose problems or explain something on the internet. It is impossible when two people are not talking about the same thing.

If you go to the articles section of this site and pull up the suspension related articles they might help you get a basic understanding of the suspension systems. Once you have that understanding you can get a truck mechanic to do the actual work under the coach. You just have to make sure he also understands the fundamentals and that he promises to not start redesigning the system. If he does, you slap his hand.

[Joe]

I have read quite a bit of the information on this site as well as Prevost related information. Watched videos on YouTube and any other information I can get my hands on. At 42 years old my patience haven’t matured to level where I can go without my coach during college football season for that long but better than having issues created by someone who doesn’t understand the system.

I am taking the coach down to the DFW Prevost Service Center for the air system work and I am going to replace the entire system due to its age–all bags and related items to get it updated. Just a PITA to get it down there but worth it in the long run. Thanks for the input.

Making my punch list now to get it updated on some other items as well and going to add an awning.

Boomer Sooner!!!

[Archived]

Chris,

When I picked up my coach last October, I too was concerned about the air system so I decided to replace all the air bags, all norgren valves and many of the push pull valves that where suspect. I also zero’d out the coach with new tires, batteries, belts, shocks and had everything serviced including the air system. Jump forward one year……When I park the coach in the barn and go out after 3 days the front end drops quite a bit and after a week or so the air guages are at about 30-40 psi….when camping and have it in level low and the auxiliary compressor on it does just fine.

Anyway, I’m on my way to Jeff’s next week to see if we can find out why it kneels so quickly. Jon has given me a list of items to check so I sent that to Jeff. My point is since you are taking it to Dallas, it is worth it to have them really check out the valves that aren’t being replaced as well as everyting else that uses air. I wish I would have known more when I did mine so I could ask more educated questions but I didn’t. I’m “almost” there with my air system and hopefully this tweeking at Jeff’s will get me to a leak free coach……for a few months anyway….LOL

[Glenn]

JUST SO NOBODY FAILS TO UNDERSTAND I AM GOING TO EMPHASIZE A FACT THAT IS APPARENTLY DIFFICULT TO ACCEPT:

IF YOU PARK YOUR COACH AND TURN THE KEY OFF (COACHES NEWER THAN AROUND 1995 OR OLDER COACHES WITH THE REVERSE LOGIC UPGRADE) YOUR PNEUMATIC SYSTEM AIR PRESSURES MEAN NOTHING.

YOU CAN HAVE A COACH DROP DOWN EVEN THOUGH ALL THREE AIR SYSTEM PRESSURES ARE AT 120 PSI, AND CONVERSELY YOU CAN HAVE A COACH REMAIN AT THE HEIGHT IT WAS WHEN PARKED EVEN THOUGH ALL 3 AIR SYSTEM PRESSURES DROP TO ZERO.

There are coach or converter specific exceptions to this, such as a leveling system that is active with the key off that is always attempting to maintain the coach in a level position.

[Greg]

“I am taking the coach down to the DFW Prevost Service Center for the air system work and I am going to replace the entire system due to its age–all bags and related items to get it updated. Just a PITA to get it down there but worth it in the long run. Thanks for the input.”

I am taking nothing away from the quality of work you will receive at Prevost DFW. I have had work completed there, Houston, many visits to Nashville Prevost and I am going to Prevost Mira Loma later this week. I have always been satisfied with their work and their care for my coach. When things were not right they made it right every time. I value my relationship with the poeple at Prevost and I intend to maintain that.

However if you want to save a pocket full of money and still get personal attention to your coach it would be worth the drive to Jeff’s in Tennessee. Yes, even with the extra fuel. If it is difficult for you to find time to get to Dallas then I am sure it will be much harder to get to Vonore but if you could plan a stop as part of a trip I think you will be glad you did.

I just had air bags, brake chambers and all norgren valves replaced at Jeff’s in June. I was completely pleased with Jeff, his shop and his work. Plus I always learn a lot when he works on my bus. One thing I learned this time is that replacing all that stuff does not solve all my air problems. That is going to require a place to work on it myself and lots of patience. I have neither of those at the moment.

Davy

[John]

I think you would do yourself a very valuable favor by getting a quote for the work you plan to have done. Davy is on target with his suggestion and I think that unless the Prevost pricing policy has changed you will not only pay for the extra fuel if any, you are going to have enough money left over to justify the additional time you might spend.

[Archived]

Besides that Jeff’s place is really comfortable….big big grounds (to walk the dog), parks close by to venture out to AND you get Jeff who will explain things as he is doing them and takes the time to suggest and fix anything else he may find. If I’m close to prevost and have a problem I’ll go there BUT when I’m traveling to Florida from Michigan Jeff is right on the way!