Viewing 15 posts - 1 through 15 (of 20 total)
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    • #2572
      MyPrevost
      Keymaster

      What is the typical aux air pressure for most coaches when parked? For instance, with the engine off and the coach stationary, what are the on and off pressures for the air compressor?

      Mine triggers around ~80 psi and turns off at ~100 psi.

      Hector

      #2574
      MyPrevost
      Keymaster

      Hector,

      My setup is similar—my aux air system kicks on at around 60 psi and off at about 90 psi. Primarily, we use the aux air for things like operating the bed lift and occasionally airing up bicycle tires.

      #2575
      MyPrevost
      Keymaster

      Hector,

      60/100 for toilet only.

      #2576
      MyPrevost
      Keymaster

      I’ve adjusted mine to turn on at 40 psi and off at 80 psi. With these lower pressures, the pump doesn’t have to work as hard, and everything still operates properly: doors, bed lift, door lock, floor slide (though it’s not needed, it still functions), generator air bags, and the dump valve.

       

      #2577
      MyPrevost
      Keymaster

      Hey guys,

      I’m not sure how to start a new topic, so I hope this old thread works. For those noticing I’ve been posting more frequently lately, it’s because I have some free time to tinker each day.

      Here’s my issue: When I turn the ignition key to the “on” position, I hear a distinct hissing sound coming from the right side drive axle area. The sound stops when I turn the key to the “off” position. The engine runs fine, and there’s no escaping air when the key is off. However, when the ignition is on and the hissing starts, activating the Country Coach-installed leveling device high on the front ceiling immediately stops the hissing. It seems that the leveling device shuts off the escaping air, but when the air escapes, the on-board air compressor’s pressure drops.

      The coach doesn’t have any leaking air bags, and the selector switch on the left panel is in the correct position. What could be causing this hissing sound when I turn the key on? Is there a leveling device in that area? I’d prefer not to crawl under the coach, even though I have bus blocks. I’m concerned that varying air pressure and weight could be problematic.

      Any thoughts?

      Thanks,
      Pres

      #2578
      MyPrevost
      Keymaster

      Reagan,

      Congrats on the free time!

      When the key is off, the air bags are isolated from the rest of the bus’s air system. When you turn the key on, the air bags are managed by the ride height valves. With the key on, the HWH leveling system activates and takes control, putting the Prevost system into “drive” mode. This suggests that the hissing might be coming from the ride height valve. If that’s the case, let the coach reach its ride height and see if the hissing stops.

      You should be able to feel the air coming from the valve in front of the drive tires if that’s where the leak is. The valve looks like this, with the hose pointing straight down connected to the exhaust port, where the leak would occur if it’s an internal piston and o-ring issue. You should be able to check this safely without needing to get under the bus.

      #2579
      MyPrevost
      Keymaster

      Gil,

      That sounds like a solid plan! I’ll check it out tomorrow. It’s reassuring to know what I’m looking for since I changed these out on the ’87 Newell I rebuilt back in 2004.

      Thanks a lot for your help. By the way, where are you guys located? We’re in Houston and had some unusually cold weather last night, which delayed our tee times this morning.

      Best, Reagan

      #2580
      MyPrevost
      Keymaster

      Houston, and Texas in general, does seem to have gotten colder the past couple of years.

      I’m on Florida’s Nature Coast, about 75 miles north of Tampa. We’ve had some good weather so far, but there were a few mornings recently where it hit 40 degrees. The good thing here is if it gets too cold, we can always drive south. Unless you’re planning to cross the border, there’s not much further south you can go!

      #2581
      MyPrevost
      Keymaster

      Gil,

      I checked the coach and noticed it was leaning to the left for the first time ever. I started the engine and let it run for 5 minutes, then turned it off—no noticeable leak. When I turned the key on, the hissing started. I inspected both ride adjustment valves, but neither seemed to be leaking. The air leak is quite pronounced, coming from somewhere between the two sets of air bags (port and starboard), closer to the port side, where the coach was leaning.

      It’s like there’s an open valve, causing a significant amount of air to escape. Tomorrow, I’m taking the coach to a truck shop with a long pit, so I’ll be able to see exactly where the air is coming from. It’s so pronounced that it should be quite evident.

      If you have any additional thoughts or tips for my search, I’d appreciate them. For now, I’ll have to wait until tomorrow to get a better look. I don’t think the air bags themselves are causing the problem, even though the air pressure eventually decreased on one side for the first time.

      By the way, you can travel 200 miles south from here and still be in Texas! I was talking to some folks from Tampa today and have a connection there; we meet in Sarasota sometimes. If we meet up, I’ll bring the coach and we might get together.

      I’ll keep you updated on the leak mystery. Thanks again for your help!

      Best, Pres

      #2582
      MyPrevost
      Keymaster

      Took the coach to a shop and put it on a rack. In front of the over-the-road evaporator coil of the Country Coach installation, which hangs down between the drive axle tires, there is a support beam going across the coach. Attached to the wall forward of the beam and opposite the evaporator coil is a valve with three or four hoses connected to it. Two of these hoses go out the bottom and curl upward through a “gathering” of other hoses and electrical wires. One of these hoses has a hole in it.

      I assume these hoses lead to the air compressor at the front of the coach but am not certain. Above the valve and out of reach, the two hoses from the valve are clamped together by a plastic tie-down that has worked a hole into the hose. The air escaping is prolific with the key turned on but stops if I engage the CC leveling system. Once the engine is off, no air escapes.

      I plan to call CC representatives who might provide guidance on whether these hoses go to the compressor. My immediate goal is to determine if these hoses can be replaced and if new hoses can be pulled through the existing portals.

      The picture on the left shows the hose with the hole coming off the bottom of the valve and extending upward. The picture on the right shows the actual hole in the hose. The area is difficult to access, even while standing and reaching up. I’m considering if these hoses might be accessible by removing panels in the water heater area.

      Thanks to everyone for following along.

      Pres

      #2583
      MyPrevost
      Keymaster

      Your line that’s leaking is the one coming from the side of the ride height valve in that rear corner, as shown in the photo Gil posted. Not to or from the front. There should be two valves there side by side. The leaking line is the one attached to the corresponding rear corner.

      With the correct supports in place, the tires do not need to be removed. It’s less than an hour’s work and about $20 in plastic 3/8 line and fittings. The fitting at the ride height valve end is 1/4 pipe to 3/8 compression. The fitting at the valve is 3/8 pipe to 3/8 compression.

      The other line coming in from the bottom of that Norgren spool valve is coming from the Norgren air manifold under the driver’s area. It produces or lets out air when you hit the up and down button at the driver’s seat or when in auto level. The top line is going to the air bag.

      The two smaller black 1/4 in lines on the ends are the signal lines. One is energized when in driving mode, the other when you are in level mode, or when the CC auto level is turned on.

      When you turn the key off, neither signal is present. If the valve is completely air-tight, you can pull every line out of that valve except the top one going to the air bag, and that valve should maintain pressure to that particular corner of the suspension. That’s actually the way to bench test those Norgrens right on the bus.

      #2584
      MyPrevost
      Keymaster

      Joe is pretty much the king of Prevost air systems, so there’s little doubt in questioning what he says.

      The Prevost air system is often considered the most complex subsystem on the bus. This complexity primarily stems from the lack of a clear, comprehensive description of its logic and controls. Although there’s a drawing available from Prevost, it’s still challenging to fully understand. For instance, the XL model’s drawings don’t include information about check valves, which complicates understanding the system’s logic. Even self-proclaimed experts can get tripped up, despite their experience with replacing every Norgren air control valve on their coaches.

      I spent time with a Prevost Service Manager who is highly knowledgeable. Together, we examined both the air system drawing and the illustrated parts breakdown. We found that while the illustrations had discrepancies—such as air lines running from different places—the system functionality remained consistent. The logic was clear: both drawings achieved the same goals despite the differences.

      From the drawings and your description, it appears that the two Norgren valves you’re referring to are Level Low control valves. These 5-port valves control the air flow to the suspension based on whether the Level Low or the ride height control valves are engaged. The air lines go to the air bags and to the 5-port electric/air solenoid manifold located under the driver’s area. CC uses the HWH controller for automatic leveling when parked, which takes over from the manual Level Low control switches. I can confirm that the blue air line is specific to the suspension system, but without further details or seeing the setup, I can’t specify which line goes to which port.

      #2585
      MyPrevost
      Keymaster

      Thanks for all the great guidance. I’m going to try handling this myself for now, but I’ve got a mechanic on standby just in case. The explanation has been a huge relief.

      I really appreciate the help and will keep you posted on how it turns out.

      I owe you all some Cajun Chicken Spaghetti or at least some true Texas BBQ. On a lighter note, I saw an article in the Wall Street Journal yesterday about BBQ in Austin, Texas. The author mentioned that when he picked up the brisket, it “literally fell off the bone.”

      Q: What’s wrong with that statement? A: Brisket is a combination of two muscles and doesn’t have a bone!

      I wonder if the folks in NYC will catch that one?

      Pres

      #2586
      MyPrevost
      Keymaster

      We did have some excellent diagrams and schematics on here that Hector had developed. I don’t know why they are still not in the Articles section. I think they were deleted because the link was no longer active. Hopefully, we can get Hector to re-post the information. He is also very knowledgeable about the air system.

       

      #2587
      MyPrevost
      Keymaster

      I found the hoses and the ride height adjustment valves they are connected to. It’s difficult to determine which hoses go where because of the harness, until they can be disassembled from the harness and traced.

      I’ve decided that this is beyond my risk tolerance and don’t want to be under the coach without professional assistance and supervision. Therefore, we’ve opted to fully support the coach with appropriate supports and two 20-ton jacks. We will then remove the driver’s side dual tires to gain complete access to the offending hoses. From there, we should be able to identify the actual hoses with the holes and determine which ride height valves they service. I see that this is a necessary job, but being under the coach is concerning. I’ll leave this to the professionals.

      Thanks again to everyone….

      Pres

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