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Air system overhaul
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As I hit the books in an attempt to understand the system better, I may be getting a little smarter. The sounds I’m getting from the AD-9 dryer have convinced me that one or more of the five valves in it are leaking. On my first rebuild years ago, I only replaced two. With leakage at that end of the system and my seat and door cylinder leakage at the aux end, all it would take is check valve leakage at the secondary tank to bring the entire system down (I may be wrong again, but at this point, I’m assuming that the primary tank check valve is the delivery port check valve in the air dryer). That theory may be somewhat weak in that most of the time all three gauges come down together when I would expect them to drop at different rates. On the other hand, there are times when the secondary tank stays at full pressure for several hours after the other two have dropped to zero. Pinpointing multiple simultaneous malfunctions is like balancing three balls on each other, but with luck, I will prevail.
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The air dryer only feeds the wet tank so if it is leaking back through an internal valve in the dryer your primary and secondary tanks should be unaffected.
What you might be facing is multiple issues simultaneously doing the unexpected. If the PO never maintained the air system it is possible the protection and check valves didn’t work, but that did not mean you would lose air.
Only when something else started to leak did the fact the protection and check valves not work become apparent. It is not unusual for a valve to seat properly and seal sometimes while leaking other times which is all part of the great conspiracy to drive you crazy.
Just as a general comment, those who defer maintenance on any issue sometimes run into a failure of a system or a problem with a system that does not make sense and often it ends up being a combination of loosely related problems that collectively produce the puzzling type problems. That is why I often suggest when a suspension starts acting goofy such as not coming to ride height, or losing the ability to go up or down if the system is old it is usually far cheaper in terms of time to just replace it all. Things like protection valves, check valves, relay valves, parking brake valves etc are pretty cheap and for not a lot of money and a bunch of good fittings you create a trouble free system and never do learn why is was messing up.
I think Peter follows that philosophy. Me too.
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Oops! You’re right, Jon… wrong tank! I’m not all that smart yet, but I’m getting tired of studying. I’m ready to start bending wrenches and replacing stuff. It’s time to put the books away and go get dirty. Even though I enjoy those “aha” moments, I agree that since everything needs to be replaced anyhow, the sequence doesn’t really matter. And although this computer helps me avoid stupid moves, the leaks aren’t going to stop while I’m spending hours typing. Thanks for your help. I’ll check back in later…
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The longer you procrastinate on the computer, the longer your hands will stay clean.
who said that?
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Easy for you to say, Jim. 🙂 My fingernails are dirty, but it feels good. I learned the wet tank check valve is indeed in the air dryer even though the Prevost parts manual exploded view doesn’t show it (but it is listed). The primary tank valve is at the forward end of that tank. Hands on discovery sure beats book learnin’. I found no evidence of problems with the air dryer valves, but they’re coming out anyhow. Stay tuned for more…
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Ron, just curious how you`re supporting your bus when you get under it ? Ramps, jacks ,etc?
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Ron has support stands.
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