Re: Air Dryer Rapid cycling? Reply #25 – August 11, 2014, 04:12:13 pm Quote from: acousticart – August 11, 2014, 04:03:25 pmMichelle,It is the one mentioned in the links you posted, though it is not internal to the Air Dryer on the DA33100- but rather screwed into the Air Dryer input ½" pipe thread port. Here is a repost of the picture of it taken apart with labels; Thanks Don - just trying to educate myself. I can often remember snippets of posts I've read enough to search for them, and use the forum's assistance to put the bits together so I can understand them and hopefully pay it forward in the future. Quote Selected
Re: Air Dryer Rapid cycling? Reply #26 – August 11, 2014, 05:23:52 pm Update: while waiting for Superior Industrial Friction to call me back when their tech guy returned from the bank, I decided to crawl underneath and just make sure all my air line connections were good. While down there, I noticed that the elbow which has the JIC sitting that goes to the governor via a 'Tee' on the other side of the air dryer was not quite as vertical as it was before. So I tightened it ever so slightly and snugged the governor unloader port line a tiny bit (less than a thirty-second of a turn). Still waiting for a callback, I started it up and watched it build to just over 120 psi heard the purge valve release as it should and then waited for the inevitable sucking sound a few minutes later and the subsequent purge. After about five minutes, it hadn't happened! I raised the coach back up on the air springs which of course dropped the pressure back down to around 90 psi and watched the pressure build back up to 120 psi and heard the purge valve unload the compressor. I ran it for about another eight minutes, and still no cycling. Now maybe the gods on Mount Olympus are laughing at me for thinking that I did something to improve the situation, or perhaps the engine finally warmed up enough to cause the Vaseline coating on the isolating valve's piston to allow it to move freely. At this point, I really don't know. Those black O-rings may not hold up for the long run, but I found A NOS isolator valve on eBay for $25 plus $10 shipping which I will have sent to my son in United States and have him forward it to me here in Canada. Then I should have it covered, if it is indeed the isolating valve that was the issue. Nothing else that I can think of would have been affected by anything I did since this problem started. Tomorrow I will be able to road test it for 30 minutes or so and should know more. If it cycles normally, I will have the confidence to let this go for the time being and just enjoy being a tourist. Thanks again for all the helpful suggestions and for your moral support. I will certainly updates after the road test and let everyone know how it goes. Assuming all is good, I will attempt to write up a summary of the whole experience with as much information as clearly stated as I can. I'm sure somebody on the road sometime in the future will be faced with the same situation and if this thread or others like it can help them like the people of this forum helped me, then it will have been worth it.PS: still no call back from the tech guy at SIF... I will certainly update the thread if they do call me back. Quote Selected
Re: Air Dryer Rapid cycling? Reply #27 – August 11, 2014, 05:32:38 pm Good for you Don!I hope that's the end of it! Quote Selected
Re: Air Dryer Rapid cycling? Reply #28 – August 11, 2014, 06:55:25 pm Don thank you for the technical description along with the sharing what you found out. Quote Selected
Re: Air Dryer Rapid cycling? Reply #29 – August 11, 2014, 07:04:19 pm Don, I think you found your air leak! Hope that was it. Quote Selected
Re: Air Dryer Rapid cycling? Reply #30 – August 11, 2014, 07:09:26 pm Great news. I've been watching on the sidelines, not wanting to clog your bandwidth until you had it licked. Hope to see you back on the road again, and soon. Tom Quote Selected
Re: Air Dryer Rapid cycling? Reply #31 – August 11, 2014, 08:00:37 pm The tech guy from SIF called back, though I missed the call. He did leave a message with a call back number. I will wait until my road test tomorrow as we move from a friends driveway to an over priced campground (they pretty much are all overpriced up here compared to the states ) where we can dump and spend a couple nights with 50AMP and full hook ups. If an issue with the dryer shows up, I will call them back. If not, I will happily be done with them. My experience with them is hard to quantify because there really was no other shop to compare them with so I am happy that I was able to find them. They may have done the job competently, but there were some telltales that concerned me (like the slathered Vaseline and 'O' rings of inappropriate material in the isolation valve material). Anyway, hopefully the 'O' rings last long enough for me to get the new isolation valve I bought from eBay.More on this tomorrow...Don Quote Selected
Re: Air Dryer Rapid cycling? Reply #32 – August 12, 2014, 07:12:09 am Quote from: acousticart – August 11, 2014, 05:23:52 pm.........................I decided to crawl underneath and just make sure all my air line connections were good. While down there, I noticed that the elbow which has the JIC sitting that goes to the governor via a 'Tee' on the other side of the air dryer was not quite as vertical as it was before. So I tightened it ever so slightly and snugged the governor unloader port line a tiny bit (less than a thirty-second of a turn). Still waiting for a callback, I started it up and watched it build to just over 120 psi heard the purge valve release as it should and then waited for the inevitable sucking sound a few minutes later and the subsequent purge. After about five minutes, it hadn't happened!.................................Those black O-rings may not hold up for the long run, but I found A NOS isolator valve on eBay for $25 plus $10 shipping which I will have sent to my son in United States and have him forward it to me here in Canada........................................Don,Based on your description of last evening and your initial posts, I'm pretty sure I know where the problem is. I believe that you are on the right track with the isolation valve.I will try to write it up tonight (busy today, so can't do it right now). It's a little complicated -- more easily discussed than concisely worded.If you want, call me anytime today and I'll talk you through it -- just can't write it up until later.603-seven seven zero-7459Neal Quote Selected
Re: Air Dryer Rapid cycling? Reply #33 – August 12, 2014, 12:09:16 pm Thanks Neal. We are moving to a park today about thirty minutes away and will have a chance to see if it behaves normally now. I would like to give you a call after we get there and and get your thoughts about it as I am eager to learn as much as I can about the air system.DonQuote from: Neal Pillsbury – August 12, 2014, 07:12:09 amDon,Based on your description of last evening and your initial posts, I'm pretty sure I know where the problem is. I believe that you are on the right track with the isolation valve.I will try to write it up tonight (busy today, so can't do it right now). It's a little complicated -- more easily discussed than concisely worded.If you want, call me anytime today and I'll talk you through it -- just can't write it up until later.603-seven seven zero-7459Neal Quote Selected
Re: Air Dryer Rapid cycling? Reply #34 – August 12, 2014, 11:45:46 pm Quote from: acousticart – August 11, 2014, 03:20:23 pm.................Since rebuilt air dryer was installed, the pressure builds normally and at approx. 125PSI indicated on the dash gauges, the Purge valve releases air as per normal. there doesn't appear to be any oily residue from this discharge as I can place my hand below and feel the air escaping and there is nothing to wipe off after the purge. Approx. 3 to 4 minutes after the purge cycle completes I hear something that sounds like a vacuum sucking sound for just a few seconds and 30-45 seconds later it purges again. All without a noticeable drop in indicated air pressure on the dash gauge........................Don, OK.With Cummins engine running; after an air tower blow down (purge), what would create a 3 to 4 minute duration "unloaded" compressor condition, followed by a few seconds of vacuum sucking noise, then a short (30-45 second) compressor loaded condition, terminated by a normal air tower blow down (purge), all with minimal to no change in the front and rear air tank pressures?First, we need to understand how a Holset engine driven air compressor is set up.Compressors are only designed to be "worked" (loaded, compressing the "siphoned off" turbocharged air) 10% to 30% of the time (depending upon designed max. air system use). 70 to 90(+)% of the time they should be running unloaded (which still robs HP, but to a much lesser degree). In general, compressors rob horsepower, they rob turbo-compressed air whenever they are compressing air and they waste a LOT of turbocharged air whenever the air dryer is in active blow down mode. They also waste fuel due to the lowered turbo boost pressure whenever the compressor is loaded and even more turbo boost air is lost while the air dryer is unloading. They are oiled by engine pressurized oil. Clearly, some tricks are needed to make the HP burden on the Cummins engine as low as is reasonably achievable.The most important design trick is using the Holset compressor as a GAS SPRING whenever the compressor is unloaded (isn't needed to be charging the wet tank). In order for this "unloaded condition trick" to work, the compressor intake and discharge valve(s) need to be simultaneously sealed and held tightly shut. The intakes are shut by the D2 Governor unloader output control pressure, and the discharge valve(s) are shut and held shut by the air dryer isolation valve being shut as soon as the Haldex Pure Air Plus starts to blow down (purge). With the intake and discharge compressor valves sealed tightly, the Holset compressor piston causes the Cummins engine to work during the compression stroke, but after top dead center, compressor work is returned to the engine as the compressed air expands (minus friction losses), thus the Cummins gives and gets some work energy as the GAS SPRING cycles -- remember, 70 to 90+% of the time). Now look at the purpose of the Haldex Pure Air Plus isolation valve used with a Holset engine driven air compressor. Without the isolation valve, whenever the air dryer is in the unloaded (purged) condition, there is a direct pathway from the compressor discharge valves to open atmosphere through the dryer purge valve. So the isolation valve has to seal tightly, AND HOLD the compressor's last high pressure stroke, in order to provide backpressure seating on the Holset compressor's discharge valve(s).So, if the isolation valve internals do not seal tightly or the hose fittings on the isolation valve machined block do not seal perfectly AND HOLD 125'ish PSIG air, what happens? Well, with the Cummins engine running; after an air tower blow down (purge), depending upon how long it takes for the Holset compressor's discharge valve(s) backpressure to bleed down through partially defective isolation valve internals or through a tiny amount of isolation valve machined block FITTING leakage, (maybe 3 to 4 minutes after blow down?) then the Holset compressor's discharge valve(s) will start to flutter open. Now the GAS SPRING is gone. With the outlet valves fluttering and the Holset intake valve(s) still tightly shut, there will be a few seconds of vacuum sucking noise as the piston draws oil and air by the piston rings on each piston down stroke. The D2 control pressure will bleed through the isolation block a bit until the D2 Governor shifts and the compression cycle starts again. But the wet tank hasn't bleed down much and the good wet tank outlet check valves don't let the front and rear air tanks bleed back through the wet tank to the defective isolation valve or fitting defect, so there follows a very short (30-45 second?) compressor loaded condition terminated by a normal air tower blow down termination (purge), all with minimal to no change in the front and rear air tank pressure indication.Don, because, in an early post on this, you said that you initially found the Haldex Pure Air Plus purge valve outlet area to have a large amount of oily residue, I wonder if the isolation valve perhaps started this and, even though rebuilt, it may be helping the problem to be inconsistent or to continue. At any rate, the isolation valve rebuild o-rings color seems to be suspect. Compressor outlet temperatures may be 250 F (+). Also, it is critical to soap test all dryer/compressor vicinity air system fittings in both the loaded and unloaded condition (stop the engine with the air dryer loaded and again stop the engine with the air dryer unloaded -- so that you don't confuse the symptoms, if you find any). A tiny Holset compressor outlet fitting leak or a tiny Haldex Pure Air Plus purge inlet air fitting leak would allow your described symptoms because the compressor discharge valve(s) rely upon trapped high pressure air to overcome compressor valve spring pressure to HOLD the discharge valve(s) shut.I think that you are on the right course with a new isolation valve and leak tight fittings.That's my current take,Neal Quote Selected
Re: Air Dryer Rapid cycling? Reply #35 – August 13, 2014, 01:31:33 am Nice write up Neal! It will bear some careful rereading and so I am bookmarking and pasting in a note pad of coach related tech... I want to thank you for taking the time to do it. I don't know if I have it chapter and verse yet, but I believe I understand it much better. The gas spring makes sense to me, but I certainly have a lot more to learn about this complex system and especially how the different systems work together. Our road test today showed that it is behaving better, but I think there is still a small leak. My next move will be to install the new isolation valve when I get my hands on it, barring a turn for the worse. I am certainly happier knowing the air dryer is keeping moisture out of the system than driving in a bypassed condition.DonQuote from: Neal Pillsbury – August 12, 2014, 11:45:46 pmDon, OK.With Cummins engine running; after an air tower blow down (purge), what would create a 3 to 4 minute duration "unloaded" compressor condition, followed by a few seconds of vacuum sucking noise, then a short (30-45 second) compressor loaded condition, terminated by a normal air tower blow down (purge), all with minimal to no change in the front and rear air tank pressures?...I think that you are on the right course with a new isolation valve and leak tight fittings.That's my current take,Neal Quote Selected
Re: Air Dryer Rapid cycling? Reply #36 – August 15, 2014, 02:10:06 pm Don,One more thing you need to check that pertains to the isolation valve set up. You have found the air line that goes from the isolation valve to the wet tank. If you follow it to the wet tank it terminates on top of the wet tank more to the curb side. (you may be able to see it over the top of your right side duels) It should be hooked up to a brass 90 fitting on top of the wet tank. If you remove this fitting you will find that in some cases it is a check valve also. If this is stopped up it won't let the air pass to operate the piston in the isolation valve. (if it partly stops up it will cause a strange squeal under the bed after you stop for the night) This is just more food for thought as you seem to have gotten most of your problems under control.Pamela & Mike Quote Selected
Topic: Air Dryer Rapid cycling?