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A New Problem
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Sometimes exercising the suspension will get a norgren working, where before it wouldn’t. The spool may have been stuck and now is moving. Jon will go into more detail I’m sure.
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I suspect you are dealing with several issues. The first appears to be the chamber that lifts the tag and while replacing the diaphragm is not risky due to the low spring force (unlike an emergency brake which is dangerous), but often it is almost wiser economically to just replace the chamber. That appears to be one issue.
It is possible the three port Norgren which holds the path open between tag and drive air bags is part of the issue. At the core of the issue however is the aux air system is losing air at a rapid rate if tag air is dumped in 20 to 40 minutes, so by fixing the chamber and making sure the Norgren valve is OK those repairs are like taking an aspirin for a brain tumor. The real problem is there are likely to be aux system air leaks that have occurred over time and were ignored and now if you have an aux air gauge it is likely to be waving at you because aux air is being lost at an excessive rate.
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Thank you…
My gauges are steady. It is when I stop and turn off the bus that the air goes down. I have been chasing leaks since I have owned this bus and the guys here have helped a bunch. I will never get close to finding all of them without a way to access underneath on a regular basis. The ONLY time I have seen the bottom of this bus is when it is up in the air at Prevost and I sure can’t afford to chase leaks some where north of $100 an hour.
I don’t have any fluctuations on air when the coach is running since I replaced the drive axle brake chamber back in February after this episode.
DKO
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If your gauges are steady but the aux air drops in 20-40 minutes that means you do not have an aux system air pressure gauge. The gauges you are seeing are your two brake systems.
Our coaches have three air systems. Two brake systems and an auxiliary air system. The brakes systems are just that. They are exclusively for the brakes and until they are satisfied with about 75 PSI the air in your bus will not be delivered into the aux air system. I suspect you are seeing your air pressures fluctuate but do not recognize it as such since aux air is supplied after the brake systems the aux air drops, and then pressure from the brake system feeds into the aux system to maintain its pressure.
Our coaches typically have a lot of uses for auxiliary system air, ranging from the suspension to the air door lock to horns, to driver’s seat to toilets, pocket doors, generator air bags and belt tensioning bellows. Depending on the age of the coach there can be other uses for air as well such as wipers, shutters, transmission retarder, slide seals and even a bed lift. Every one is a potential leak point and only keeping after leaks is a coach apt to be reasonably leak free. Ignoring leaks is OK to a point, but after a while as the leak rate increases the engine driven air compressor is working harder and longer. Out of control leaks such as a large one in an air bag have the potential to shut you down unless your air systems check valves and protection valves are in working order, something that needs to be verified for your safety every time a technician is under your coach.
Finding leaks at $100 an hour will stop most folks because leak detection is a painful process that takes time and multiple methods. But if you ever get an opportunity to start chasing leaks because you have access to a pit or support stands take advantage of it. Hector has what we all consider a leak free coach and I believe he will echo my comments about aiming towards that goal. He has developed the skills and methods needed to know where and how to look and I hope he can jump in here to suggest ways to start “picking the low hanging fruit” to use his phrase.
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I read Tom’s post from this morning, then went to take my leaner to Marathon. Lo and behold, there was no lean! The drive home must have loosened up something!
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Bonz, since leaks in air bags and at air fittings usually do not repair themselves an intermittent leak that creates “the leans” is typically associated with a Norgren valve. In coaches with slides the system is designed to dump tag axle air when the slides are operated so we can know you exercised the three port Norgren valve and since you tipped your coach one way and then the other when in the campground we know you exercised the other two valves in the left rear where you were leaning. In other words you exercised every valve in your leveling system and if one of them was the culprit causing the leans just exercising it has corrected the problem, probably temporarily, but that could be for months or even longer, or it might act up again the next time you use the coach.
The good news is rather than trying to chase a leak that is now not a leak you can either wait until it shows up again, or buy about $300 worth of Norgren valves, replace the three for about 2 hours of labor, not worrying about which is the defective one and your bus is fixed. When the leaks are associated with the valves they are very difficult to detect.
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Just having it hold off a while will be nice. That way I can get everything done with one trip to the shop.
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That makes perfect sense. One thing I noted when I spent some time under my coach was that some of the suspension system connections are the push in type as opposed to the compression type. Over time that type connection is more likely to show a leak than the compression fittings. I am not advocating a wholesale replacement of fittings, but I would take the opportunity to squirt soapy water on them every time I am under the coach.
Also, as a coach and its components in the supension age colder weather tends to make the coach lean quicker, probably showing up leaks that were always there, but the cold making them larger.
Chasing leaks ain’t for sissies.
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I’m looking for time to visit a friend in Tenessee who will help me chase them down…. If he can stay up past 8 pm, anyway!
You need to update your signature. It is still showing some old bus.
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Leak detection often requires cold beer. I need to get some new pictures, but technically my signature is still correct since I have the coach listed.
If you want to play under the bus, are willing to get dirty and greasy, a lot can be accomplished to get you comfortable with how everything works. But a word of warning………I am still a student. The principles are the same, but this bus is different than the older one.
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I renewed alll of mine that were not destroyed in the fire.. Had to replace 3. Not a big job all the bores and pistons were perfect showed no scratches or wear patterns. So I just refreshed the O-rings and seals plus a little lube and things are good to go. Suspension test has been on for 3 days and all is good. Bob
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Jon…
Just add the new bus leaving the ’97 on there…. that way we will feel better knowing there is another 2 bus owner out there !!! -
It is fixed…
I called Worldwide Equipment in Cincinnati. (Business Card Below) They are listed on the Prevost website as a certified repair center. They sell and work on Volvo so they do more work on Volvo engines in Prevost busses than they do on the rest of the Prevost systems. They were upfront about that on the phone but they were pretty sure they could take care of the air leak I described.
They lifted the bus while it was running and I lifted the tag so they could spot the air leak. The mechanic could not find a leaking valve underneath but found the big leak was in the canister on the side away from the tire. When he took it apart the rubber diaphragm was not in terrrible condition but it was completely out of place.
This is the connection below the canister and he discovered that the pin and clevice and was frozen and would not allow that rocker arm to move properly. He thinks this put stress on the whole system and pressure on the diaphragm and moved it out of its proper place in the canister. It took him quite a while to “unstick” the joint for lack of a better word. Even though the diaphragm wasn’t bad he replaced it since we had a new one and it is so cheap. I am sure it has been in there for years, possibly 17 years.
Here is a picture of it from the other day…
The folks at Worldwide Equipment were very helpful, especially Dan the mechanic that actually did the work. I was in the shop about 4 1/2 hours and they tried to charge me for just over 3 hours labor even though they were waiting for the diaphragm most of the time. They did knock 1/2 hour off without any hesitation.
It would have cost me about $175 in diesel to detour from my route to Prevost in Nashville. They could have fixed it quicker but it would have had to be almost 2 hours quicker to save me any money and I would have spent 5 hours driving. Worldwide was 25 miles from where I am this week.
All in all it was a good choice and now it is fixed. Thank you all for your help and advice.
God Bless,
DKO
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Glad you found someone close and it always helps to hear about good service facilities. Good job…
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Don’t most shops work or charge hours by flat rate , ia, the book says it takes 1.5 hr to change part they do it in 1 hr they still charge for 1.5 hr kind of a bonus for a better machanic. Thats how they are able to give a estimate. If it takes 2 hr they still only charge by the book 1.5 hr.
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