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Internal??? air leak ft suspension
OK, I’m a little lost; checked the articles, etc; but I figure one or more of you gurus can help.
With suspension locked, air is lost from the front system. Every other leak I’ve ever fixed has been relatively easy to find. In this case, it sounds like I’m losing air from a leak on the rear strg compt wall but I have been unsuccessful in finding any leak with spray bottle and stethescope unless maybe it’s behind rear partition wall.
I have noticed the sound of air moving through the valves/lines in the past pressurizing the system. I wonder if what I’m hearing is actually air moving through the system from the air bags to the aux system through a failed valve or solenoid and not leaking externally (except through several minor aux system leaks, of course). ?????????????
1999 XLV X-6872, liberty #440 -
26 Replies
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Joel,
If your front is going down my guess is it is associated with the air bags, a fitting, an air line or the valves associated with the front. I think yours allows air to escape the 3 port valve on the steer compartment bulkhead when lowering the front. If the leak is internal to the valves plug where the air escapes after you have confirmed which port it is. If the front stays up the leak is associated with air leaking internally through the Norgrens that are to lock air in.. But the Norgrens can also leak to atmosphere past the end O rings and escape out either end of the valve. That usually shows up with soapy water on the valve.
I don’t believe any air loss in the rear of the bus will be associated with the front settling down.
I think with your IFS you might have the two three port Norgrens over the front axle so it could be those valves also but they don’t exhaust front air bag air. They just direct the flow of air.
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No way air could be leaking back into the aux system?
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How old are your airbags? When I replaced mine a few years ago they were all dated 1999 and I was really glad to get them replaced. I don’t think any were leaking but they were starting to show their age. I looked at a 2001 XLII last summer and it’s airbags were likely original as they looked very similar to the ones I pulled off mine. If you have already changed them out then check this off your list.
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Joel, it might be possible, but the easiest way to determine that is to keep the aux system pressure higher than the approximately 100 PSI it takes to raise the front to the driving height. To do that you need two Norgrens to have the same internal leaks, the control and air supply valves.
If it is leaking back, it will also leak into the air bags.
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We were having an intermittent issue with the front brake air gauge falling below 60 psi while in storage or even in just one night at an RV park. Or, it would hold 138 psi for weeks.
We found out that the front aux. compressor behind the bumper had a bad ‘air compressor quick connect’. The compressor was coming on about every 17 min. and running for about 30-45 seconds. It was nice that I could turn off that compressor from the Crestron pad.
With the engine running, a constant flow of air was coming out of that ‘quick connect’. Replacing the quick connect cured the issue. I found it surprising that the aux. compressor was tied in to the front air brakes as that compressor supplies air to house items (dump valves, air doors, etc.). I had it fixed at Signature Coach Works in Beaumont, CA, on my way to service in Mira Loma for a chassis lube and fog light lens replacement (rock hit).
Prevost Mira Loma told me that if there was a black hose running to that compressor that it was tied into the front brakes (it has that black hose). Prevost Miro Loma checked the whole air brake system just to be sure and found everything tight and in perfect working order.
Signature Coach Works diagnosed the problem, replaced the ‘quick connect’ and checked the system in 30 min. Excellent service and very fair pricing!
Mark
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Failure of an almost brand new “quick disconnect” air coupler. Interesting. Did you examine it to try to figure out why it failed and where it failed?
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Dick,
I think it failed because it started when we were in frigid temps. Maybe there was a little moisture in there that caused the problem.
Mark
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How frigid? Do you think it “froze” and that broke it?
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Dick,
Eight degrees. Yes, I think that the cold temps had something to do with it as when the compressor tried to come on it made a terrible noise. Once we were in normal temps, no more noise. The progression of the running cycle increased as the weeks when by.
Mark
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Mark,
138 psi, was that a typing error, I hope?
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I always put a ball valve before the the quick coupler so that never happens I can shut it off and open it when I need to use it, I am talking about the quick coupler to use for airing up tires or using a blow gun for dirt in steering bay, if that’s what you are talking about , or maybe you meant a air line quick coupler for air lines
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Tom,
The needle is just below the 140 psi mark on the gauge…. so, I said 138.
Peter,
Yes, the quick connect for an air line that you might use to air up the tires.
Mark
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If your maintaining 138 psi, I would suggest you have a governor problem, 125 is the highest air pressure you should have for brake and aux air.
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Tom,
I will be in the coach today and I’ll check for the exact number.
If my number is correct, Prevost service didn’t say anything about it as I specifically had them check the system for the air loss.
Mark
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Your dryer has an internal governor and is not adjustable, if it’s bad, it has to be replaced. The old style like I have has an external governor at the compressor and is adjustable.
Give Prevost a call, I think 138 is concerning…
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