[Archived]

Zmax………perhaps Hector will jump in here and add to my comments.

First, if your suspension causes the coach to lean to the right it is not associated with the front. That problem is solely in the RH rear unless you are simultaneously leaking down in the front also. The rear controls your left to right leaning. If you want to rule out the front as being a part of the problem, lower both sides in the rear, leave the front up and if it hasn’t gone down after a period of time you know it is OK.

I am not familiar with the HWH, but I believe it always tries to keep the coach level as long as their is aux air available. If you can turn that feature off do so because it might be masking problems or giving the illusion of problems. I am speaking specifically with causing the aux compressor to run every 30 minutes.

Once you know to which direction the coach leans you can more easily zero in on the cause. However, and this is my opinion only, if your air bags and Norgren valves are original and you intend to enjoy your coach for quite a while, don’t even diagnose why it leans, just replace all of them. Shop for the best place to do the work if you do not do your own because the variation in price can be as much as 100%.

Assuming the aux air leaks are not associated with the suspension you will have to find the leaks and fix them. Again, having someone you are paying chase leaks is a very expensive and time consuming process. You may want to do some basic leak detecting if not all of it yourself. All of us who have chased leaks can tell you there is no easy way to find them. It takes patience and a willingness to get a little dirty.

Your aux compressor will not introduce moisture into the aux system if it has a water separator or moisture trap that you can drain as required. When any pneumatic system on our coaches gets water logged it is due to lack of maintenance. Both the engine driven compressor and the aux compressor have the ability to deliver moisture downstream. But the systems have protection in the form of a dryer (engine driven compressor) or water traps or separators (aux compressor) that require periodic maintenance.

[Archived]

If your aux compressor is running every 30 minutes, you have a
pretty good leak somewhere. Most of the HWH systems were used in
tandem with the Prevost system and used aux air to maintain a level
bus 24/7. If the controller sensed an out of level condition, it
would add/dump air to the appropriate airbag. Air up the bus and
turn on your aux compressor and HWH and as it makes corrections, you
may be able to identify a leaking bag if that is the problem.

With the HWH off, Jon has told you how to figure out where the
leak is, most likely in the rear. For what it’s worth, anytime you
have a suspension leak, cold temps will make it happen.

[steve]

Does the Aux air supply to the HWH or just items like seat,louvers,air slide ,etc?

Jacksonville prevost inspected all bags, leaks ,etc back in warm WX and found & replaced a few misc leaking push-in fittings with compressed type. Have always noticed that when stopping engine AUX air begins to bleed off from 120 psi to 0 fairly rapidly and the HWH immediately lifts the left side out of level. When I reset the HWH it will level up & a few minutes later it will begin lifting the left side even though it`s level. I`ll level up today and do as Jon suggested.

I`m planning to replace all norgen valves soon & bags ASAP. I`m trying to get educated on how the system works, been under & all around looking for those darn leaks.

[Bob]

Jon, I find only three locations, two in steering bay & one in engine bay for brakes, to bleed air system besides the tank valves in the wheel wells.Are there more ? I do get water when bleeding steering bay.

[steve]

First, I strongly suspect the HWH is masking problems. If there is a way to turn it off, do that and leave it off until you are done chasing problems. When it comes to pneumatic problems such as leaks I cannot think of anything else on our coaches that equals that as far as giving us fits while allowing others to vacuum our wallets.

Once you have turned off the HWH so it is out of the equation then it becomes easier to determine if your coach has serious leaks or if the HWH is taking air trying to level the coach.

One thing everyone absolutely has to understand: (HWH OFF!) With the key off the aux air system can drop to zero pressure and the air should still be locked in the suspension. With the key off air from the aux system should be locked out of the suspension. The 5 port Norgren valves at each of the suspensions (front, LH rear, RH rear) block the flow of air into or out of the suspension system with the key off. The suspension is receiving air from the aux system only, and only with the key on AND THE HWH IS LEFT ON IT CONFUSES ANY EFFORTS TO ISOLATE ISSUES.

As to where to service and drain the pneumatic system, there are air tanks beneath the coach. A typical coach has a “wet” tank, primary and secondary brake tanks, and an auxiliary air tank. If the air dryer element is changed routinely and the tanks are drained at every service interval (6200 miles) you should expect a bit of moisture from the wet tank, maybe a spoonful, but no moisture from any of the tanks downstream. If you run the aux compressor often you can expect to remove moisture from the water trap or separator(s), and possibly the aux air tank.

If more moisture is removed than descibed above make every effort to get the system serviced and as necessary dry out the system before moisture does any damage. Moisture in any part of the pneumatic system is bad and if allowed to remain can corrode valves or even prevent working components from functioning.

The tanks in the wheel wells should be bone dry. They are essentially adding volume to the air bags (for lack of a better way to describe their purpose) and if any moisture shows up while draining them you can bet the entire pneumatic system has moisture in it. Those tanks can be drained, but keep in mind when you drain them the bus will settle down. Never ever get any part of your body beneath a bus that has not been supported when you drain those tanks unless it is supported at the chassis support points

[Kevin]

With you on chassis supports! I`ll fire it up later today, turn HWH off and report back with result.

How is the “Wet tank”, pri/sec brake tanks & aux tanks bled ? Where are the air dryers located & assume they have filters to replace ?

Wheel well tanks are bone dry !

[Paul]

Steve,

Unfortunately, managing pneumatic leaks are part of Prevost
ownership, at least it has been for me.

My comment is it sounds like you may have several leaks that
could be making it difficult to troubleshoot the issue. If you take your leaning issue as one
separate problem, solve that, then move to the others. As Jon has stated, the coach suspension is
designed to trap air in the suspension air bags when the key is off. So, if you leave the key off and the coach
leans, get a spray bottle of soapy water and start looking. 95% of leaks I have found has been in
fittings. I have never has an air bag
leak, not to say it could not happen. I would assure the coach is properly supported and spray all the tubing, fitting connection and air bag on the leaning side. Keep it wet until your have checked all components. It
takes time to find and repair these minor leaks, hence, your success with a
commercial shop will vary.

Once you isolate and repair the leaks in the suspension
system, then start other systems. I
consider the coach has three pneumatic systems: brake air, suspension air and
aux air.

You are 100 percent correct to think that leaks will
increase with cold weather, that is a fact.
Rubber components contract with cooler temp, thus more leaks.

As frustrating as it can be, Prevost leaks are
manageable. It just will take some Time
and Patience.

My coach had so many long term leaks when I purchased it, I
was overwhelmed at first. My attempts to
have Prevost repair the leaks ended unsuccessful?? Thus, I created the interactive presentation
that is posted on this site. Once I understood how the suspension system works, then it was simply a matter of finding and repairing the leaks.

If you would like to chat about areas to isolate high probability
leaks, send me a private message with you telephone contact and a good time to
call. I always enjoy chatting about bus
stuff.

I offer this warning to all.
Never, never, never crawl under your bus unless you have it properly supported.
The Prevost suspension system is dynamic and being under the bus when
the suspension releases will cause death or injury.

Again, these Prevost suspension systems are complex, but
offer a one of a kind ride. Once the leaks
are resolved, it should last a long time before additional maintenance is
needed. At least, that is the experience
with mine.

Good Luck,

Hector

[JIM]

Hector, thanks agn for the prevost suspension system video. I`m sure it was a real undertaking.

Results: 33F outside, started up with HWH off. Travel mode.

1. Aux air 0 to 120psi @ 3mins.

2. Systems air normal, left side raised past level, front slight low & remained.

3.Lowered rear & shut down w/ HWH still off. System stayed as is. Waited @ 45mins.

4. Checked right rear for leaks as much as possible w/o getting underneath.got to wait on better WX for underneath. system remained as item 3.

5.Restarted w/HWH off. Item 2 resulted.Turned HWH on. System worked for @ 5mins resulting in front slightly low & right side slightly high. Remained.

5.Turned HWH off. Travel mode resulted in item 2.

6.Engine shutdown w/HWH on. system remained with left slightly low. Aux air 120psi to 0 @ 3 mins.

Any ideas ?

[steve]

Steve,

Locating and isolating leaks is a long term process.

Based on how quickly you responded and outlined the performance I would guess you did not allow sufficient time to allow things to happen.

If a coach leans in an hour the chances are you might be able to actually hear the leak. But if it starts to lean overnight you still have a leak, but it will take some effort to find it.

I would temporarily disable the HWH. Turn it off or pull a fuse or breaker or do whatever it takes to prevent it from operating until you have learned how your suspension and aux air are functioning.

I would start with airing up the coach and with it at the driving or ride height, the aux system at normal max pressure I would turn off the key and measure from the bottom of the bay doors the distance to the ground at that time.

Then at each hour I would record the aux system pressure (aux pump off) and the height measurements originally taken.

Those records will tell you if you have aux system leaks and if your suspension suffers from the leans. Remember at this point with the key off you are measuring two different things since your suspension could leak without affecting the aux pressure, and conversely your aux pressure could be leaking without affecting the suspension.

Once you have the results you will know two things for sure. You will know the relative health of your aux air system and if it has leaks you have to fix or if it is acceptable, and you will learn if the front suspension, left rear suspension, or right rear suispension have leaks. While I agree with Hector about fittings, especially push in fittings being a major source of leaks I know air bags and Norgren valves also leak over time.

As to questions regarding where to drain the wet, primary, secondary, or aux tanks, each has a petcock at the low point accessible from beneath the coach.

[Archived]

You are right Jon sufficient time is important, but wanted to get some idea of how the system was operating. The Aux air goes to zero in abt 3 mins after shutdown, so I realize that`s another set of leaks besides the suspension. For now we`re holding level w/HWH off & will see what happens as the temps drop tonite. I like you`re idea of tracking the heighth each hour & will pursue.

Got a good source for Norgren valves ?

Hector, when my private forum is set up I`ll email with contact info. Thanks guys !!

[Larry]

An aux system that goes from 120 to 0 in three minutes doesn’t have a leak, it has a blowout. You should be able to hear that leak.

I have never been lucky enough to have a single leak so big it was easy to find and it was the only one. My leak detection efforts always seemed to be many small almost imperceptible leaks that were found one at a time with a lot of effort.

[Gerald]

Having picked coach up from Prevost Houston Saturday (yesterday) trying to isolate leaning (bus was up at Ft Worth 4 weeks ago with same problem (no fixie but sure chargie) It’s down on left side (drivers) this morning. Replaced all airbags this trip plug more valves. Replaced 3 valves up in Ft worth 3 weeks ago. It was leaning on other side when taken it. Go figure. Gonna figure how to get this up in air, blocked with jacks and look myself. I don’t think It will go back with this problem. You can throw thousands at this in Prevost shop and still have the problem. Good Luck Steve.

glen s.

Ps.

Had drivers window fixed with fog issue. Got one thing fixed. Yee Haw! Will let you all know what they hit me on ticket. Service manager said he ran out of ink figuring bill out and would email it to me for payment. this week. Gonna tell him Obama”s sequester will delay payment!

[Rick]

This is directed to Glen and possibly Steve, but may be of interest to all.

I have replaced or participated in the replacement of air bags and Norgren valves on about 10 coaches. In almost every case I had to tweak the installation to find a leak that went undetected when I did the final check.

It may not seem like a big deal because each air bag only has one fitting. But those fittings can have other fittings so just at each air bag alone there may be several potential locations for leaks. If the Norgrens are being replaced the number of potential leaks increases significantly. One coach owned by friends leaned over two mornings in a row, and in each case it was an air bag. The crimp between the top plate and the rubber “bellows” was deficient. The amazing part is my friend was able to find it. She lucked out in that the air bag was oriented the right way so she could see the bubbles when she squirted it with soapy water.

I have had brand new Norgrens leak and I learned to bench test them before installation. I made a rig out of parts from Home Depot to insure the valve was bubble tight before I even installed it.

My point is simple. If our coaches are leveled to ride height the ride height valves will only allow enough air to level the coach. The smallest drop in pressure after the key is turned off will begin the leaning of the coach. So I check for leans from ride height position because they will appear there quicker than any other way. If I took my coach to anyone for repairs I would wait three days minimum before picking it up and would direct them to park it outside. I would call every morning to ask if was leaning. If it was I would ask them to fix it on their dime. It is bad enough to pay someone to renew the suspension. It gets worse when you pay for them to repair what should have been done correctly. I am not saying it is easy, I am saying getting the fittings leak free, especially old ones and ESPECIALLY push on fittings is difficult.

As to how to safely support the coach I use these, with the hydraulic part all the way down and the screw adjusted up to the uderside of the chassis support point with the suspension fully raised.

http://www.harborfreight.com/automotive-motorcycle/bottle-jacks/20-ton-air-over-hydraulic-jack-95553.html

I also use jack stands, but whatever you use just make sure it is under the chassis support points.

[Clifford]

Thanks Jon for the reply. Coach stayed at prevost almost 2 weeks this time with air issue. Checked (called) every morning and it was a different side each time after work on air system. Seems like they were chasing side to side then front. They ordered Front leveling valve they said was leaking and installed Friday. Picked it up and the tech said no leaks at new airbags. It had been in shop overnight there was no lean when I backed out of there shop. Shop is heated. Parked it outside overnight (as Folks are doing work on my Bus Barn) and temp got down to freezing. Have read that cold temps will accelerate the problem.

Ps.

When you go to Prevost admin site on this forum and read about there new Houston location that’s my camper in the left side next to that yellow banana.

[steve]

Jon, after more than 24hrs coach has settled slightly to the right and level front to backn I did hear the aux air “blowout” in the steering bay & whem WX breaks I`ll diagnose using your & Hector`s advice knowing it`s a long education process with safety foremost.

It`s sad that Prevost doesn`t have trained & experienced tech`s to diagnose these problems instead of a witch hunt. My experience with Jacksonville Prevost was not impressive in this arena, but with other repairs it was very satisfactory.

Thanks guys!