OK, my next project is changing out my Pure Air Plus.
My main question is it best to take it out first and go to like NAPA and have them get me a refurb, or just order it and then take the core back to them?
If I take it out first I guess I should zip tie baggies of the hoses?
Thanks
When we replaced the drier in our 36, we purchased the remanufactured drier from NAPA on a Saturday. (Many times they offer discounts for different products at different times of the week.) When the part came in we picked it up and payed a Core Charge. That charge was returned to us when we brought the old one back to NAPA.
Have you recruited a friend to help? it's a big heavy unit and it is sometimes difficult to get to. Two makes it a lot easier than doing it alone. Just sayin.
Good luck.
Thanks Scott, that is not to bad then, lets one get all the needed items off the old one that are needed ^.^d
Order it first and take the core back,when we did ours I ordered the 2 kits but wanted to do it once just to see how it went together,
the rebuild does seem like a better option.
Thanks John
That is a very important point! Sometimes the rebuilt units do not include all the necessary fittings. Also, having both units sitting side by side on your bench insures that you get the fittings aimed in the correct direction. There is little, if any, slack in the hoses so it's critical that the fittings all point the right direction.
Your dryer
may have a external "Isolation Valve" attached to it. If so, the rebuilt unit will not include this valve. It is good practice to replace this valve when the dryer is replaced. You can order the part online from several sources - shop around for best price. See below:
Haldex Isolation Valve (http://beamalarm.com/Documents/haldex_isolation_valve.html)
KN23500 by HALDEX - VALVE CHECK (https://www.finditparts.com/products/368725/haldex-kn23500?srcid=CHL01SCL004-Nall-Dall-Gusa-Snbr-Mbrd-K_dynamic&gclid=EAIaIQobChMI_8DAtdeA3QIVBZ7ACh3dqggjEAAYASAAEgK24fD_BwE)
Thanks Chuck, this is my isolation valve right?
(https://photos.smugmug.com/Foretravel/Forums-post-1/i-VVKDkP6/0/46bd456a/L/20180203_145628-L.jpg)
NAPA gives you 30 days to get the core back to them for a refund.
That is the isolation valve. One other point to consider... the fittings can be very difficult to break loose, so you may be well served to break them loose while the dryer is still mounted on the coach. The JIC fittings on the air lines will readily come apart, but the fittings that is actually screwed into the dryer are pipe thread and will likely be very hard to take out while the dryer is loose on the bench in front of you.
Don
Thanks Don, I will take my big crescent wrench and a bit of pipe ^.^d
I went to NAPA and talked to then and he said they list 6 different ones and they have different fitting sizes :o
guess I will clean the old one up and use a paint pen to mark the directons of the fittings and NAPA said he would pull the fittings to measure the sizes.
The air dryer reman Haldex # DA33100X
Loosen the fittings before removal as they can be really tight and the bracket holds it well.
Bill Willett just gave you the number that you need to order. It is the correct one. Get it bring it home and than change the fittings from the old to the new and then take the core back. It is much easier that way.
I ordered it the afternoon and it should be here tues, I called Haldex and they gave me the number for the idolater for it and I ordered that too. so next Wed I will go put that in. ^.^d
I just might get it done so old phart phred can come see it in 3-1/2 weeks "LOL"
Well I got my dryer and I am getting ready to install it and a couple of questions have come up.
How can I be sure all the air has been bleed out? I have put my stands in and opened the petcock on the rear tank and dumped the air from the suspension but the gauges still show 85 psi.
then for this part with the wire do I remove the one from the old dryer and use it or do I cut the wires and solder this one in?
Thanks
(https://photos.smugmug.com/Foretravel/Forums-post-1/i-Fv4WzKV/0/1de8e7b9/M/20180828_080350-M.jpg)
(https://photos.smugmug.com/Foretravel/Forums-post-1/i-GkGfRqL/0/6345bdbb/M/20180828_080613-M.jpg)
Cut and solder, or butt splice..... I did mine by myself back in January, not to bad. Like everyone else said break the fittings before you loosen it from the frame. If I remember right it's an inch and an eighth wrench that you need for the big connections. I had to use the fittings off my old one, they weren't too hard to break they were tight but they did come loose just noticed the position that they're in before you break them loose that's how they need to be when they go back so the hoses will hook up properly. If you bleed the air down by opening the wet tank there shouldn't be pressure on that side and there may be a little bit but not much between the compressor in the dryer on the other side. I don't remember any surprises when I did mine. Did you pump the brakes to see if the air pressure went down from 85. If I'm not mistaken the air pressure is read from the two air tanks at the front of the coach after the wet tank and I believe there is a check valve between the wet tank and those two front air tanks. I'm sure there someone that can correct me if I'm wrong. If you were closer I would offer my help. Good luck.
Cut and solder, or butt splice and heat shrink.
Crack/ Loosen the hoses a half turn slowly,let out the pressure .
Wear safety glasses. maybe that shoud be the first line??
Yes solder/shrink/grease, or use the old wire if it looks good.
The Front and Rear Brake Tanks still showing 85 psig is good. That shows that your Front and Rear Brake Tank check valves are seating and preventing air pressure from returning to the wet tank. But the Front and Rear tanks need to be vented (drained) periodically also. It is not mandatory, but this is a good time to drain them and discover if there is any moisture or powder that has found its way into the brake tanks.
If I were doing it, the existing on-board plug (for the heater) should be identical and, if in good repair, I would reuse it without concern. I would put a dab of dielectric grease on the male part of the connections. Then I would save the new plug as a spare part. If the plug is not identical, then I would need to figure out the wiring and splice in the new.
HTH,
Neal
Thanks guys, I will cut and solder with heat shrink.
I am a bit leery of bleeding the front tanks yet until I see how the stands I cut fit, the front will probably be down in the morning. I was having a hard time getting the stands on the rear as the rear was losing air pretty fast. I would get one in place and have to go back in and raise it and then run back and stick the next one in.
Is the rear tank just to catch water and then the air moves to the front tanks or do the rear brakes get their air from the rear tank?
The rear tank, which is properly called "The Wet Tank" to avoid confusion, is supposed to catch/retain any moisture that gets past the dryer.
The rear brakes get their air from "The Rear Tank", which is one of the 2 tanks at the
front of the coach.
The front brakes get their air from "The Front Tank", which is the other tank at the
front of the coach.
How tall are your safety stands? They should be 12" tall for easy insertion, with about 1/2" of clearance to spare.
When you are trying to insert your safety stands, is the engine running? If so, when you release the "RAISE" button, the coach will immediately try to return to ride height.
Using the "RAISE" button, you should be able to raise your coach all the way up to the top of the mechanical stops with the engine running. Then, before you release the "RAISE" button, shut off the engine. That way, the coach
should remain in the fully raised position while you take your time carefully inserting the safety stands.
If the coach will
not remain fully raised using the above procedure, then you have some bad leaks either in the air bags or in the air lines going to them. Our coach has a number of small leaks somewhere (?) in the air system, but it will stay in the fully raised position for
weeks before it finally starts to settle down onto the safety stands.
If operating correctly, your air bags should retain whatever pressure is in them, even if you completely drain all the pressure out of all 3 air tanks. There are check valves in the 6-pack manifold blocks that should prevent air from flowing backwards out of the air bags.
Thanks Chuck, I understand now, so the gauges on the dash are reading the two front tanks then
Thanks Chuck that is what I was doing wrong, I was leaving it running and try to run around the coach when I measured it so I cut the rear ones at 9" and the fronts at 10".
I think this time around I can get by with the 9" in the rear and it might even be better for me and my short arms "LOL" I can remake them latter as I still have (2) 11' and a 6 ' pieces left over from a previous project, they are the same size as the width of the frame rails and heavy wall. It only took me about a hour to cut and deburr all 8 last night.
I will probably have to rebuild the 6 packs after November and the bags will deflate in about 24 hours.
Yes. Verify that the check valves have not failed:
Open the drain by the left rear wheel and remove all air from the wet tank.
Close the valve.
Half hour or so later, re-open the drain valve. If any air comes out, one or both check valves have failed.
Thanks Brett, I drained the rear tank yesterday and closed the valve, I just checked it and not even a small puff came out.
I took off the mud flap and I have plenty of room to work. I got the little horses loosened but the 2 big ones are soaking in power blaster, they dont even want to budge, I will give them another shot before I leave and then come back in the morning. :) I have already soaked my shirt :'(
Steve, you may give those a bit of heat ( just slightly warm)with a small touch or heat gun the spray them. Also a little TAP with a hammer in the CCW direction may also help.
Thanks Beane, I will bring my heat gun tomorrow, I need it any way for the heat shrink
Don't be discouraged - just keep working on them and they will eventually let loose. It took my longest wrench, augmented by a 2' cheater pipe and my total body weight (160# soaking wet), to break them the first time. I think mine were installed by a 500 pound gorilla on steroids!
When you finally get around to reinstalling the fittings on the new dryer, do yourself a favor and put a dab of "anti-seize" on the threads. You'll be glad you did on the next R&R.
Permatex Anti Seize Lubricant 0.1 oz. - Ace Hardware (https://www.acehardware.com/departments/automotive-rv-and-marine/fluids-and-lubrication/anti-seize-lubricants/87644?x429=true&cid=CAPLA:G:Shopping_-_Catch_All&k_clickid=6e2445b4-207a-4044-a716-b49cbaebdd42&gclid=EAIaIQobChMI_9mm3L2S3QIVBrnACh0nbQ96EAQYBSABEgIgRvD_BwE)
Thanks Chuck, I have some good silver antisieze dope.
Well I have the new one ready to put back in but it will be Sunday or Monday mornings but where do these to?
Thanks
(https://photos.smugmug.com/Foretravel/Forums-post-1/i-3JVpMFn/0/59273030/L/20180831_191920-L.jpg)
Hi Steve,
I hope your air dryer replacement goes smoothly. We put on two newly rebuilt units and both had the wrong psi safety popoff valve installed. Not knowing how/if your coach differs from ours. Psi of rebuilt unit was 175. Psi should have been 205 or 210. I believe there is info on Beamalarm regarding this. Sorry I don't have a link for you but sure someone here will speak up on that.
We now have our old unit reinstalled. Only serviced the filters. I believe the Pure Air is obsolete, hence only rebuilt units are available. I would like to go with a different air dryer manufacturer in the future.
Thanks Mike J, are you taking about the pressure in the tanks? mine was about 110 -115 psi on the old one.
Our "defective" rebuilt ones had wrong popoff/safety release valve on them. Shop doing work didn't catch it. Apprently Cummins knows this issue exists on rebuilt units but didn't tell us until we asked. I recall some talk here or on Bealalarm about it. FT uses a higher psi than usual. Not sure about NAPA ones.
This isn't the psi in the tanks. It is only the air dryer safety popoff. Once system reaches max pressure. Cutoff at 130psi
I think there might some confusion about the terminology here. The purge valve on the air dryer is part of the normal cycle of the compressor being unloaded when the D2 governor reaches its set point, it causes the purge valve to open which is what you hear when the set PSI is reached. The pop off valve on the wet tank (normally 150 PSI) shouldn't release unless there is some problem with the governor or purge valve. It is there to keep the tanks and other parts of the air system from rupturing and to protect the compressor. At any rate, it is the D2 governor that that maintains the air system at the appropriate safe pressure to operate the air brakes, suspension, etc. Some people like to set the governors a little higher, say between 110 psi and 130 psi (usual range of 20 psi between cut off and cut in). The ones I have bought from Freightliner or Napa have been preset at 105 to 125 psi.
At least, that is my experience and understanding of the system (and I am always seeking to learn more about how these complex systems interact).
Don
Thanks Don for clarifying, some of the systems get confusing
Hi Don. From your description it seems that the D2 valve came installed with the rebuilt air dryers we had installed? Our air purging problems under acceleration ceased once we reinstalled the OEM dryer that came with our coach. Both rebuilt units we had tried purged air at a lower psi that what should have been. When engine rpm ramped up and compressor speed increased during acceleration the dryer would purge continuously for 10-20 seconds. I too am in search of a better understanding of these systems.
Iv'e had a tech use the term "load and unloader" valve on the air compressor. Is this the D2? If so why would replacing new dryer rebuilt units with our old OEM fix the low psi purging? Must be something internal bad on our two rebuilt units? I just want Steve to get correct dryer for his coach and not a bad unit or one that wasn't built to FT psi specs. Maybe my experience is we just got unlucky twice...
Did you follow reply number 5 and get an isolation valve,sounds like that may be what your talking about.The D-2 valve is located
near the engine air compressor and no where near the air drier and the air drier does not come with a D-2 valve.If the "tech" is at
the coach when he asks about the unloader ask him what he's talking about,no way any of us can tell.
I know the techs who worked on our coach wouldn't have installed anything related to air dryer that was incomplete. Word I got was the pressure relief valve on the dryer wasn't rated for the higher psi that FT required. Cummins guy tipped us off that this so called "pressure relief" valve is often not correct on rebuilt units. Wish I had more info than that. Is there a pressure relief dedicated to/and installed in the air dryer? Is the isolation valve what they are misnaming? Something was definitely amiss that was independent of air compressor. Could this explain why our two new/rebuilt dryers kept exhausting air when they shouldn't.
This from service tech email: "Michael, The rattling noise may be the compressor loading and unloading. I know that on Cummins the compressor makes a bit of noise when it is loaded up. It is normal to a point. If it starts sounding like a loud engine knocking noise that would concern me. That would tell me the compressor is not feeling well. The unloader valve may need serviced, That would be something I would have a certified Cummins Repair shop do. They get carbon build up and sometimes causes them to make noise and stick."
His description doesn't sound like a D2 valve to me.
Yes I did get the Isolation valve, the two square rubber pieces with adehivse back came with the dryer and I am not sure where they go. I will get it installed in the morning I think.
the other item in question is what should be popping off at 205 to 210 PSI that Mike J was talking about. I am not sure where mine will be until I get it installed
Steve, Nothing should ever get to 210 psi. Our gauges read 130-128 when air dryer purges. The higher amount you are referencing is what I was told the mystery air dryer "safety valve" is supposed to be set for. But honestly I can't justify you worrying about this. If your air dryer is correct in all respects for what your coach uses than you will be good to go. It seems we had unusual problems with our rebuilt units, or a bad supply chain.
Besides that the air diagrams can be different among coach builds. Air dryers seem to be common units but determining what went wrong for us has been a headache. Really don't want to muddy the waters for you.
Steve as others have said, the D2 air governor is attached to the air compressor. It controls the total maximum air pressure that can be in the system, it's what cuts the compressor off. 120-130 PSI is what they are set at, doesn't have any thing to do with the air dryer. There is a safety valve in the air system I think on the dryer that will pop off if the governor should fail. In short the dryer should never see any more than 120-130 psi.
The D2 valve is not installed on the air dryer, but is connected to it via the isolation valve on the coaches equipped with a Holset compressor. However, the isolation valve is not installed on (as far as I am aware) coaches after 1999 when they changed from using the Holset compressor which required the isolation valve mounted on the air dryer to the Wabco which does not. There are some good videos on Youtube that attempt to explain the operation of the D2 governor and its relationship to the dryer, wet tank (or reservoir), and compressor. Here is one with a cut away view of the D2;
https://youtu.be/9Vb32PL1PVU
There are others ranging for very basic explanations to more advanced trouble shooting steps for the air brake systems. As always with these videos on Youtube (or any information on the internet for that matter) consider the source and cross check where possible before arriving at your own understanding. It won't be long before you have the basics. ^.^d
Don
Mike,
The dryer has a relief valve screwed in the bottom of the unit.
There is a pressure relief valve screwed in the wet tank also.
The isolation valve don't bleed air out to atmosphere.
Pamela & Mike
Right! I forgot about that one, part of the general service kit,
150 175 PSI. Still, it isn't part of the normal loading/unloading cycle. Normally, they should never go unless there is something really wrong.
Don
Edit to correct the Pressure relief PSI setting.
In the 1st paragraph quoted above, Mike J is wondering about the pressure relief valve
which is screwed into the bottom plate on the Pure Air + dryer. I have also been confused since he first brought up this point. I think I have finally found a old thread that clarifies this question. It seems, when FOT installs a DQ6026 rebuild kit in this dryer, they do
not utilize the KN31527 (175 psi) pressure relief valve which is included with the kit. Instead, they install a KN31529 (200 psi) relief valve. It is this fact that leads to the confusing information he was getting from the techs at OMC.
Why Foretravel makes this change in relief valves is beyond me. I cannot imagine any situation where a 200 psi safety valve would be preferable to a 175 psi safety valve, especially since the air system should never (even in the event of D2 failure) exceed 150 psi (rating of the pressure relief valve in the
wet tank). The full thread is the first link below:
Haldex Pure Air Plus Relief Valve (http://www.foreforums.com/index.php?topic=28654.0)
KN31527 - Pressure Relief Valve - Haldex product (https://www.haldex.com/en/na/valves-9c82abc0/pressure-relief-valves/pressure-relief-valves/kn31527/)
KN31529 - Pressure Relief Valve - Haldex product (https://www.haldex.com/en/na/valves-9c82abc0/pressure-relief-valves/pressure-relief-valves/kn31529/)
In the second paragraph quoted above, the tech is using the term "unloader valve" but did not adequately explain what he was talking about. He is
not talking about the D2 governor. The unloader valve is a
internal part of the air compressor. It is located in the top of the compressor cylinder head. It is the mechanism that
reacts to the pressure signal from the D2, and directs the compressor to start and stop compressing air. It can get dirty, become noisy, and if not serviced, eventually (after many thousands of miles)
might cause the compressor to malfunction.
Hope this helps clear up some of the confusion.
Thanks Chuck, great info. ^.^d
The funny (sad) thing is, even after participating in that discussion 2 years ago, I have no idea at what psi the pressure relief valve on my AD-9 air dryer would open. I have changed our dryer twice since we got our coach, and never bothered to look at the valve. Now that this discussion has made me curious, I cannot (so far) find this info anywhere online! My dryer relief valve might be rated to open at 1000 psi for all I know. :o
I'm still looking...
Steve,
Nobody ever answered your question about the 2 black sticky pads. Probably because nobody knows what they're for.
My guess is they are some kind of anti noise or vibration material, meant to fit into the air dryer mounting bracket somewhere...? If there were no instructions with the dryer, and you didn't see anything like that when you removed your old dryer, then I (personally) would not worry about them. I stick mysterious little parts like that away in a drawer, and eventually (sometimes decades later) come up with a use for them.
Whenever taking my advice, remember: I am not really a mechanic, but I do portray one on this Forum. 8)
Thanks Chuck, I never found any reference to them in the short instructions that came with the dryer and it is all in now except I have to go get a eye fitting for the ground wire.
I did figure out another handy item besides a dead blow hammer is a ratchet strap ^.^d
Done, and no appearance of any leaks
Thanks everyone for your help ^.^d
now to go home and take shower so I will quit dripping on everything in the coach :dance:
Chuck,
I'm not sure why FT changes the Pure Air Plus relief valve from the standard 175 psig to the 200 psig, but I'd bet that there is a good reason. I also don't know whether that applies to all models of engines, or just those engines with Holset compressors and turbo saver valve assemblies installed.
However, I do know that the Pure Air Plus mounted relief valve has nothing to do with the coach air system(s) downstream of the air dryer. That's what the wet and brake tank reliefs are for. Instead, the Pure Air Plus Dryer relief valve is there to protect the Holset compressor and the the air dryer itself:
- If oil is blown by the compressor and saturates the desiccant and coalescing filters, then the compressor output will keep climbing until something relieves (better the relief valve set at 200 psig than the Holset).
- The same for ice in the Pure Air Plus Dryer and purge valve. An ice block could cause a lot of internal compressor and/or dryer damage - hence the need for the protective relief valve in the dryer base.
- The same for certain D2/Air Dryer failure modes that could close the air dryer isolation valve but not shift the purge valve.
With regard to your second paragraph above, the Holset compressor operates in a "gas spring" mode when it is "unloaded", to reduce horsepower burden.
Air Dryer Rapid cycling? (http://www.foreforums.com/index.php?topic=22077.msg166882#msg166882)
The "unload" pressure signal from the D2 causes the compressor intake and discharge valves to shut and each cycle of the piston, the trapped air is first compressed and then expanded (to first require work from the engine and then return energy to the engine). In Mike J's case, if the compressor is not properly operating in "gas spring mode", it might be the source of a changed or unusual "noise/rattle/clatter". But only experienced ears on the sound can detect that and Mike said that he was going to have an experienced service center give a listen.
HTH,
Neal
There
may be a "good" reason, but it certainly is not a "well publicized" reason. If this is a Foretravel policy, then it should be made very clear to owners of the affected coaches. A
BIG BOLD warning in the Owner's Manual would be nice. We'll have to ask Mike J (or other owners with the same dryer) to comb through their books and see if any such notification exists.
Still, it is hard for me to think of any logical reason for this change. Under all the scenarios that you postulate, what could possibly be the benefit of employing a
safety relief valve with a
higher opening pressure? Someone at FOT must know the reason, but who?
May be because that's what they could get at the time,or because the relief valve can be 10% either way,who knows,would put a call into James T.
Here's a better idea,if any of the men halves of the ladies driving school are out there,you will have a bunch of classes,ask away about this and anything else you can think of.
Chuck,
I don't know the exact answer to your question, but based upon Mike J's experience where his OEM Pure Air Plus Dryer with a 200 psig relief valve worked fine without inappropriate actuation, but (2) remanufactured units with 175 psig relief valves (contrary to FT specification) would inappropriately actuate whenever engine RPM was increased, my best guess would be that there are "stacked" air flow resistances (pressure drops) and engineering tolerances that drive the need for the higher (200 psig) relief valve part.
Logically, there are a lot of pressure drops between the Holset compressor outlet and the wet tank (150 psig protected) where the D2 governor control valve senses its pressure. But, apparently, at the particular point that the Holset Compressor relief protection valve is located on the PAP Dryer, within that series string of pressure drops, 175 psig isn't quite high enough (a 175 psig relief valve will lift inappropriately), at least on some coaches. But a 200 psig valve "beats" the stacked pressure drops and tolerances and does NOT inappropriately lift, while still affording protection to the compressor and dryer under blocked conditions that the D2 governor cannot see or remedy.
While it would be interesting to know, I wouldn't expect FT to explain that level of engineering detail, or provide bold cautions in an owner's manual on the use of a 175 psig vs. 200 psig relief valve on a subcomponent. If they were expected to do that, then I can think of hundreds of other engineering decisions and design basis minutiae that would be equally interesting to know.
It is more curious to me that others have not experienced this before. I know that when I have done my Air Dryer change outs, whether complete remanufactured units or kits, I either blindly followed directions or just replaced parts with like parts and it never occurred to me to question the engineering. So, either through luck or lack of curiosity, I never happened to find myself in Mike J's sequence.
HTH,
Neal
Thanks, Neal, for your concise, logical analysis of this unusual occurrence. I have to agree with everything you said. Your conclusions certainly fit the facts reported by Mike J.
What troubles me is exactly what you say in the line quoted above. Why hasn't this ever been reported before? It would be interesting to know how many Pure Air Plus dryers are replaced/rebuilt at the factory, versus the number done by owners and/or other service shops. The factory, we are told, installs a 200 psi safety valve. Clueless owners and other shops more than likely will utilize the 175 psi valve included with the DQ6026 rebuild kit and (I assume) with complete rebuilt dryers. One would presume that this problem would be fairly common. And yet, my search of the Forum archives found no other mention of a similar dryer malfunction. I did find one interesting thread on the Pure Air Plus dryer. It illustrates the lack of knowledge (among Forum members) about dryer service requirements , but nowhere is there any mention of the safety relief valve issue:
Pure Air Plus Air Dryer - An Ounce of Prevention... (http://www.foreforums.com/index.php?topic=7700.0)
I looked at the data sheet for the Pure Air Plus dryer. It indicates in a couple places that the 175 PSI valve (KN31527) is "correct" for this dryer. Does this imply that the the conditions requiring substitution of the 200 psi valve are unique to (some) Foretravel coaches?
Pure Air Plus Air Dryer Troubleshooting Guide (https://wiki.foreforums.com/doku.php?id=technical:air_system:air_dryer:troubleshooting_air_dryer)
All in all, quite a nice little mystery that bears additional investigation. Hopefully all Forum members with the Pure Air Plus dryer are now aware of the fact that the safety valve should be checked for proper pressure rating when rebuilding or replacing their dryer.
What if we were to discover that most of the Pure Air Plus dryers currently fitted to our member's coaches have 175 psi safety valves installed? Then it
might follow that Mike J's problem had nothing to do with the dryer safety valve...
Is it possible that some use higher level D2 units (130 psi rather than 120), and this increases the likelihood of safety relief activation?
I would think not, because any excess pressure situation induced by the D2 setting is
downstream of the dryer anti back flow check valve, and would be relieved by the 150 psi safety valve in the wet tank.
I wonder if it has anything to do with the difference in the engines from my 97 C8.3 and Mike J's 02 400 ISL ? and maybe different compressors?
There was a reference somewhere about the isolation valve disappearing at a certain year or build number. That is probably when the compressor brand was changed. Just a guess though.
Think were getting away from the answer,the relief valve is there to protect the air drier body,the other vessels in the system do
have their own relief valves.
My reply was for the fact that the compressors changed when the isolation valve was eliminated and that is when the issues on the pressure relief valve seem to be showing up. Holset to Wabco.
Craneman,
You may be referring to BJ Holden's (Corndog)'s summary of the long pursuit and eventual discovery of a solution to the internal/external isolation valves mystery. In that time frame, if an owner did not use the proper air dryer/isolation valve combination for one's engine, it would cause an oily mess. It was not easy to discover/understand what was causing the problem and what combination was needed:
Haldex air dryer isolation valve (http://www.foreforums.com/index.php?topic=17590.msg118355#msg118355)
As I understand it, Cummin's change from Holset to Wabco engine driven compressors plus the standardization of Bendix as well as Midland Air Dryer isolation valve designs (now universal and internal) has pretty much eliminated that issue.
I agree with you, Chuck.
I didn't want to cause Mike J any alarm and his current solution may well be a final solution, as long as he always uses a 200 psig safety on his PAP Tower. I don't see an URGENT need, but IMHO, Mike needs to have a well qualified "ear" give a listen to his compressor's "noise/rattle/clatter". Is it new owner acclimation or is there something else there that may relate to the 175 psig relief lifting? I know that the compressors on both of our coaches have struck me as overly noisy on certain occasions, but eventually I acclimated to the sound of the compressors. And just changing the D2 governor, always changes the routine sounds up a bit, as well as, the sounds change appreciably from cold iron to operating temperatures.
But, I'm still concerned that Mike may still have a unique situation that was/is driving his 175 psig relief valve lifting, because I can't believe that some undefined large population of air dryers has been "accidently" maintained with the FT specified 200 psig relief valve over this long a period of time. There have been too many opportunities for this to happen before. But stranger things have occurred , I suppose.
HTH,
Neal
Haven't done it on mine and mine runs good but I have a book on my engine that instructs about pulling and cleaning a metal
line from the air compressor that may "carbon up" in some cases,will find the book and try and find more info.
Neal,
Your description/details fit my situation perfectly. The rebuilt air dryer Haldex units had 175 psi "safety" limits. The original appears to be 200psi. (as described to me by shop tech).
The clatter noise. Good news here too, I think. There was an air leak as Chuck and others suspected. 6 months ago an air line was added from the rear brake supply to rear of coach to serve the M&G air modification done to our tow vehicle. A shop in our hometown of Medford Oregon did the work and they routed the line straight back to the receiver hitch. Bad decision. The line made enough occasional contact with the drive line to wear a hole. The air compressor was making all the air it could and was purging off at the air dryer every 2-3 minutes. Every time compressor (unloader?) would reach 130 as measured at rear tank, (not wet tank) the noise would get louder, like marbles in a tin can. Once air purge occurred the compressor would be quiet again. Escaping air was initially hard to find because once the parking brake is set a lot of air is already out of line where leak was. By time we got to Moscow Idaho it was big enough to hear standing next to coach even after brake was set.
Fixed the air line and rerouted it up and over the rear axle and zip tied to existing brake air lines. Now everything moves in sync with the suspension. The clattering noise diminished immediately and the time between air purges at dryer stretched way out. (I haven't timed it yet). We have driven over 400 miles since repair and clattering noise is completely gone now. Went to Cummins shop in Spokane recommended by OMC and they agreed about the "unloader valve, carbon build up etc. on the compressor". Head tech listened very closely to engine. Tested it three times by dumping air thru the brakes with engine off then running engine until air dryer purged. Sounds normal to him and I agree. Sweet diesel rumble and compressor noise no different than when we got coach last year.
Of course none of this answers why FT would have 200psi on our air dryer instead of 175 that everyone else is happy with. Is the change over between compressor manufacturers for the Cummins ISL a clue?? The Cummins shop in Eugene Oregon that OMC consulted knew about the problem.
So glad forum members have dug into this. I'm happy we seem okay again but not totally satisfied with my understanding of the "why it now works". I hope this thread continues for a few more postings. It also sounds like Steve has had no problems with his replacement. That's good news!