[Tim]

Alan,

Leak detection is a black art and it is not as easy as spraying soapy water and looking for bubbles. Because of that it is one of the quickest ways to have your wallet vacuumed clean of folding money.

I would never suggest to anyone that they take their coach to a shop and ask the shop to find the leaks. The reason is there have been too many horror stories about shop technicians spraying fittings all over the coach to find leaks associated with a single part of the pneumatic system. Jeff knows and understands exactly what components and fittings are associated with a coach leaking down in one spot so I guarantee you that he only spent time looking exactly at those leak points that would create your problem. He also realizes if he cannot find leaks when he starts looking by spraying soapy water he is going to his bag od tricks and use other methods, including an ultrasonic leak detector.

So your left side leans are going to be somewhere in the fittings Jeff looked at. The problem might not be the same fittings as the right side, but the problem is going to be confined to a specific list of components and fittings and valves. Your problem is to find which ones. Do not assume newer air bags or Norgrens are unlikely to be the problem. They have as much potential to be why the coach leans as a leaky fitting. To do the checking for leaks you have to be able to see every affected fitting or valve or air bag. If you have to get beneath the coach to do that you have no other option. You can safely do that as long as the coach is supported under the chassis support points. If soapy water does not reveal leaks then your options get progressively harder and ultimately could end up being checks for pressure loss at each fitting in line until you reach the point where the leaks are no existent.

You do not want to hear this but you need to either bite the bullet and have someone with the knowledge like Jeff do the work, or you have to figure out how to do it yourself, or you can take it to Prevost and hope the person assigned the work knows the system and where to look. Prevost does stand behind their work so if they failed to solve the problem after taking your money they are obligated to pay your back or find the problem on their penny.

[Harry]

Fair comments Jon.

So as I am not going underneath my coach to determine where the leak or leaks are with respect to the left rear suspension I will have Prevost do so.

Based on the pneumatic schematic I have for my coach (1999 45XL) it would appear to me that the possible leaks would be isolated to the three rear bags, their fittings, three bellow/ping tanks and their fittings and left rear three port norgren and left rear five port norgren and their associated fittings. I will instruct Prevost to inspect these areas. Are there any other possible locations that you recommend they should be investigate? Many thanks…..

[Archived]

Don’t forget the R-12 valve that is the interlock valve (turns the brakes off) when the tag axle is raised. The pilot air for the R-12 is the tag bag air (Tee between the 3 port norgren and the tag bag).

Even after new Norgren’s and bags I still had the leans until the R-12 was changed. Mine leaked internally and so soapy water did not tell the story.

Mine has the older “logic” in which when the aux air drops to 35 psi the tag dumps, but I don’t think this makes any difference on the tag brake logic. Check your diagrams.

[Archived]

Allan, you have identified the items to begin your investigation. There are some things you can check without getting under the coach by removing the fender liner ahead of the drive wheels and exposing the 5 port and you can check the solenoid operated Norgrens Liberty installs in the steer compartment which on rare occasion can contribute to the problem, but without getting under the coach or pulling the wheels you do not have the ability to do a comprehensive check.

Joe is correct in what he said and note that an internal leak on any of the Norgrens isn’t going to show up with soapy water but will often be detected with the ultrasonic leak detector. You cannot find leaks in air bags except with soapy water or pressure testing because the ultrasonic leak detector can’t “hear” a leak in a rubber component. Like I said it is a black art and the person chasing leaks requires knowledge of where to look, as well as what means of detecting works best in specific areas. Some checking can be done without soapy water by you, and that is to lift the tag axle and allow the coach to come up as high on the leaky side as possible. Leave it that way and if it remains up the leak is from the three port Norgren back, if it still leans it is likely between the three port and the 5 port.

Generally speaking however your leak is somewhere from the five port Norgren in front of the fender liner back to the tag axle air bag and everything in between.

[Archived]

Not to hard to do I replaced the 1 way check valves on all 3 of the height control valves

[Allan]

If a coach has the leans it will not be associated with the ride height portion of the suspension system.

[Larry & Diane]

Thanks everyone for their help. Yesterday I raised the tags to determine if the coach would lean or remain level as per Jon’s suggestion. Unfortunately the coach leaned left rear over a 24 hour period. The coach is with Prevost now and hopefully they can find the source of the leak from the 5 port norgren downstream to the bags. They will inspect the bags for cracks and do the infamous soap water leak test. All fittings will be soaped up again from the five port norgren to the bags. Hopefully it’s just a fitting and not a bag or norgren valve. But I am prepared….or my bank has been forewarned of the possible $$$.

[Archived]

The leak(s) could be in more than one place which makes leak detection so difficult. If it leaned over with the tag lifted it suggests the leak is associated with the 5 port Norgren back to the three port between the two axles, but a second leak from the three port back is just as possible.

Every one of us who has chased leaks, either by using a service company or by ourselves shares your pain.

[Jim/Chris]

The Dreaded Leans. I’ve spent thousands of dollars with 2 different Prevost Facilities and still have them. Mine takes about a 4 or 5 days but will start heading south. Slowly Rear end first and then left side. Never stay parked when we have it out over 2 or 3 nights and that works for us. In the barn it settles on the bags. Should have built a pit when I built this new bus barn and chase them myself.

[Dick]

I hope my comments don’t offend anyone or some of you think I’m nuts … but … I was told by my medical doctor and it was later confirmed by an audiologist that as men get older (i.e. “age”) two things happen.

One, they lose the ability to process multiple sensory inputs (like being able to listen to more than one conversation at the same the same time, or listen to a conversation and watch something on TV, or listening for the source of an air leak while someone is telling them the coach looks dumb when it leans, etc.). Second they tend to lose the hearing in certain frequency ranges, especially higher pitches where women’s voices tend to be and where the sounds that air leaks in Prevost coaches are. There is likely an advantage in one and an distinct, extreme disadvantage in the other.

For example, my wife contends she can hear two or three air leaks from the coach even while the engine is running, I can’t hear them even with the engine off. I wish I could hear those air leaks, especially when the coach is off and I could try to chase them down.

Regarding this air leak stuff, I wonder if there isn’t the potential for a little part time business of finding and fixing air leaks on coaches. I sincerely empathize with the guy from BC driving 2700 miles to ETLC to have Jeff find the air leaks. Its “only” 700 miles for me! I’m down right jealous of you guys and gals who live within and hour or two of Vonore; I hope you know how fortunate you are.

You’d think that Prevost would make it a priority to have one or two techs at each maintenance facility who were skilled in finding air leaks.

[Archived]

I don’t care who is trying to chase air leaks. The ability to understand the systems, and specifically each converter’s systems as well as the Prevost systems (every version) is a monumental task. Add to that the fact that some leaks will not be revealed by soapy water, a stethoscope, an ultrasonic leak detector or ears. Some leaks are so well hidden the only sure way to isolate them is to do pressure checks starting the beginning of a system and following the air down the system until you finally reach a point in the system where there is no leakage meaning the last place checked is the likely leak.

Of course to do that requires not only the intimate knowledge of the system being checked, but how Prevost or the converter routed the lines or located the components.

I said it previously. The best way to chase leaks is to have a wallet extremely full of Benjamins, patience, and an understanding that you have a coach with what might be thousands of potential leak points. Despite having made two coaches virtually leak free after a brain numbing lengthy process I have zero desire to expose myself to that pain ever again. I am not willing to spend what it really takes to chase leaks. I am not willing to do anything other than to fix big leaks when I find them and if I am terribly bored I may spend some time looking for the more subtle leaks but to expect anyone to be such an expert that they can quickly and efficiently fix air leaks is nothing but wishful thinking.

Some leaks have to be fixed, like problems that cause the leans. As simple as each of our three suspensions are however we still can go nuts chasing leaks associated the a few air bags. Think of Prevost ownership as an adventure.

[AL]

Success. The leak, only one, was found by the Prevost guys. It was a fitting on top of the middle drive bag.

With the information I had from this forum plus an air suspension schematic for my particular coach I asked Prevost to inspect specific areas that I thought were likely sources of leaks. I don’t know the cost for Prevosts services as the bill has not yet been processed.

I want to thank everyone for their help and especially Jon who has written very detailed papers on this subject plus his tireless efforts providing useful comments regarding questions relating to air suspension matters.

[Steven]

Great news Allen, Glad You got Her fixed !