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AD-9 Air Dryer noise… chicken or egg?
I know the old gal has a major air leak, but I’m curious about the quiet whining she does as I walk past her main wheels. Sometimes she gets more excited and moans with a lot of feeling after resting a short while. Her even louder groans are embarrassing when they attract the attention of my neighbors. She’s about as vocal when she’s warming up as when she’s cooling down. I know I’ll never understand women, but I’m anxious to know if this lady of mine is unique or do all you guys stand around whistling and looking up at the sky as she’s passing air? Does all this ruckus come normally in feeding a distant leak or is it a sure indication the leak is within the dryer itself? I’m not all that experienced, so any insights you can pass on to this old bachelor will be greatly appreciated.
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17 Replies
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Long time no see– shouldn’t be feeding back thru dryer. maybe tags bleeding off? notice any drop there? or bad check valve—– If it is comming back thru dryer it’s time for refurb. Take care my friend. Bob
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Hi Bob! I’ll try to stop by on my way south in a couple weeks. I hadn’t thought about backfeeding, but it could be happening because I failed to install a new check valve when I replaced the compressor and regulator. Yes, the tag air dumps when the aux pressure drops. Have you heard a lot of noises from your air dryer?
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no I run a wabco with a built in ck Valve but yours should have same feature— that prevents back feed. My bus not finished yet—- lost last year do to back surgery.. On down hill side now. come on by!! Bob
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Ron, Since it is hard to answer tough questions like you just posed, I’ll throw out something to consider. Could it be air flowing through a protection valve (and should not be)?
When is the last time you verified the check and protection valves were functioning properly?
When I air my coach up with shop air as I get to the protection valve opening pressure I hear a groaning sound until the pressure has been exceeded and the valve is fully open. But not at any other time.
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Excellent point, Jon. I haven’t ever checked them. Airing my coach up from shop air produces a similar sound, but it doesn’t stop, so I think we’re onto something. ‘Exactly the info I was looking for. Thanks!
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A snall I think 5/16 line on dryer activates check vale internal to dryer to prevent feed back on mine. Short term check squirt some air tool oir in the supply before you hook up your shop air and see if that clears the dry or debree problem…sometimes shop air is a little harsh for that forst stop/check valve and a little extra lube will take care of it…The oil will drop out in the wet tank…..
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Ron,
Sometimes mine will honk and moan the entire time I have shop air to it. All the ones I’ve had made strange noises with shop air to the rear fill for brake air.
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Where do you put shop air into the bus? Rick
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Rear engine access door, stbd side, this one fills all tanks. The one in the steering bay is for aux air only.
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When you guys air your bus up with shop air, what regulated pressure do you use, or does it matter?
Do you leave it aired up all the time, or just to check systems?
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I use 125 PSI which is the same as my compressor on the Detroit is set.I also have a refigerated dryer to make sure that I am not adding moisture to the system,I never find any water in any of the air tanks.
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I have a 175 PSI shop air compressor, but the dryer will spit at 120 or thereabouts. I monitor the air going into the coach and if I am going to do something else I limit the tank pressure to 120 to 130 PSI just so I don’t mess something up.
I think my shop air cuts on at around 100 PSI so I let it build to 120 to 130 and then turn it off. If I am willing to stand there I will let it get to a very high pressure in the shop air tank, but if I am doing something else I limit it since I really don’t have a gauge at the rear where I fill it. In the rear I have a quick connect fitting so I don’t have to hold a tire chuck on the fill port.
If I am only airing up the aux system up front, I do have the gauge there and I just watch the gauge. I have to be there anyway because I left the schrader valve there for filling so I am using a tire chuck.
The only reason I air things up on the coach is if I am working on something and want the coach or systems pressurized. If I don’t want to start the bus to raise it up to put on the stands is why I would do that as an example. Otherwise I just let the air in the coach alone and don’t worry about it. My brakes have air in them at something over 100 PSI and the last time I ran it was the beginning of the month. The slide seal is still at 10 PSI and the generator air bags are still at 14 PSI. the aux system shows zero. Surprisingly I was monkeying in the engine area today and the belts are still tight. I put a check valve in right after I got the coach and I am certain that is why they are still tight.
I HATE farting with the air systems and specifically chasing leaks. I would rather eat bees.
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I only use shop air if I’m working on it Jerry. This Liberty will maintain aux air forever, but the brake tanks bleed down in just a couple days. Just the opposite of other buses I have had’ usually the aux bleeds down and the brakes hold up.
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Yea Tom, Mine is just the opposite. Brakes hold a couple of days, but all of a sudden, my aux air leaks down within 30 minutes, if compressor isn’t running.
I’ve sprayed around in the drivers compartment, and have replaced many fittings and valves in there, I don’t detect any leaks there, nor in the engine bay.
I have noticed just this week, that my right front was leaning a little when I went out to the shop today. I have not had any leaning until today. I started it up, let everything build up, and after 8 hours, it’s still up.
I definitely have a bad aux leak somewhere. I don’t hear anything, and have sprayed everyting I can get to. I even bought a Stethascope (cheap $27 one).
Also, I have noticed that the 2 air bags on the rear of my Generator leak down quickly along with the aux system. But the other two front bags stay pumped up?? I have sprayed both regulators on the Gen bags. no leaks there.
Leak chasing continues……..
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Jerry,
The most effective way to isolate leaks is to develop a basic understanding of your coach pneumatic system. Keep in mind that with the key off your suspension systems are isolated from the balance of the aux air at the 5 port Norgren valves. That means that leaking aux pressure is unrelated to the leans. Fixing either one will not cure the other.
I am not familiar with how Vantare sets up their portion, including the aux compressor, but for a leak in the aix system as you describe I almost believe it can be heard. 30 minutes is a very short period of time for an air loss with a starting pressure of 120 PSI. The first place I would look would be for a failed aux compressor check valve, then at the air regulator(s) in the rear for belt tensioning, and most definitely at the generator air bag circuit. That also should have a check valve and if it leaks down that makes it highly suspect.
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