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 C2 air dryer purging too often
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buster133
Advanced Member

USA
414 Posts

Posted - 07/26/2013 :  09:12:51 AM  Show Profile  Reply with Quote
I have a 2013 6.7 ISB C2 wheelchair mini bus with hydraulic brakes, air parking brake and air ride suspension giving me issues. The air pressure gauge on this bus stays a little above 125 psi and the air dryer will purge itself about every six to eight seconds. When the bus is running and the parking brake is released, the pressure on the gauge only drops a touch below 125 and then builds right back up and starts purging again. Iíve checked all the lines in the immediate area around the dryer with soapy water and didnít find any leaks, Iíve also replaced the small ľ hose from the front of the compressor to the dryer because it had a slight kink, but that did nothing. Iím not that familiar with these setups because my fleet is 95% hydraulic brakes. The bus isnít losing any air pressure, it just seems like itís producing too much air and doesnít know what to do with it. Is there a new air dryer or governor in my future? The bus has only been in service for less than a year and has 14K on the odo. Any ideas, tips, suggestions? I hate to throw a bunch of new parts at such a new bus if itís something simple I havenít figured out yet.

C.HARDY
Advanced Member

354 Posts

Posted - 07/26/2013 :  10:16:21 AM  Show Profile  Click to see C.HARDY's MSN Messenger address  Reply with Quote
I would say a little trash in there would do the same thing but that bus is awful new to have that problem...

"Hardybusman"
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Bassman
Top Member

USA
512 Posts

Posted - 07/26/2013 :  12:23:20 PM  Show Profile  Reply with Quote
Try listening to when the compressor kicks in and then shutting the bus off and listen for a leak. If the line that runs from the compressor to the govornor (if you have a remote mounted govornor) is leaking, it will give this symptom. At least it does on my Mercedes buses. On the Mercedes, it is usually a leaking plastice 1/4 inch line running from the compressor to the gov. or the quick disconnect fitting on top of the compressor. Yours may be a different set up. Good Luck
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tigger2
Advanced Member

USA
284 Posts

Posted - 07/29/2013 :  04:44:04 AM  Show Profile  Reply with Quote
What make and modle of air drier do you have? Have you drained the air tanks especialy the wet or first tank in line from the compessor. Is the air governer mounting tight? You checked the lines what about the purge valve on the drier after the pop off some units purge the line air on the feed line but hold the governer pressure, is yours leaking it all off?
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ICFrank
Active Member

United States
27 Posts

Posted - 07/30/2013 :  07:27:17 AM  Show Profile  Visit ICFrank's Homepage  Reply with Quote
I agree with Bassman. I had a 2010 IC do the same thing. The line at the air compressor had a small leak. Repaired it and have had no further problems.
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buster133
Advanced Member

USA
414 Posts

Posted - 07/31/2013 :  03:02:11 AM  Show Profile  Reply with Quote
I had already replaced the ľ plastic line in hopes that it would have fixed the problem, but it didnít. This bus has the AD-9 dryer, and it doesnít have a wet tank, just a single primary tank. I didnít have any leaks that I could detect with soapy water and the bus wasnít losing any air, even overnight. Anyways, I picked up a reman bendix dryer and a governor, replaced them both at the same time while it was apart so I don't know if it was one or the other but the bus is functioning as it should, for now. Thanks guys

[URL=http://s7.photobucket.com/user/buster133/media/6f2e0703-1970-4ac9-bb1f-b6b9d7c12297_zps1741e113.jpg.html][/URL]
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Thomasbus24
Administrator

USA
3335 Posts

Posted - 08/01/2013 :  11:38:02 AM  Show Profile  Reply with Quote
Hang on to the AD9 and give it to your Thomas rep next time he is in. No reason you should have to pay for that. I'd put my money the check valve or the purge valve...both can cause that issue. AD9 is still the way to go though...good job to whoever spec'ed that particular item!
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Bus Tech II
Senior Member

108 Posts

Posted - 08/01/2013 :  11:43:15 AM  Show Profile  Visit Bus Tech II's Homepage  Reply with Quote
I have only seen this one time, and after fixing minor leaks, changing governor, the only thing that totally fixed it was replacing the whole dryer assy.
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buster133
Advanced Member

USA
414 Posts

Posted - 10/02/2014 :  08:39:13 AM  Show Profile  Reply with Quote
Now I have the same problem on the sister bus. So far Iíve replaced the ľĒ line from the compressor to the air dryer, replaced the AD-9 with a rebuilt and replaced the governor. The problems went away for about two weeks, and then constant purging problem returned, went away for half a day and now is back purging itself just about every ten seconds while the bus is running. Iíve checked all the lines I can see underneath with soapy water, and when the bus is off there is no detectable leaking sounds and no loss of pressure over night.

This bus also requires a parked regen about once a week because itís only used in town and does a lot of idling when loading and unloading wheelchairs, not sure if that relates or not. Anyone have any ideas? Canít afford to tie it up @ the dealer since itís my only 3 W/C bus!

[URL=http://s7.photobucket.com/user/buster133/media/6f2e0703-1970-4ac9-bb1f-b6b9d7c12297_zps1741e113.jpg.html][/URL]
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willism
Senior Member

United States
142 Posts

Posted - 10/02/2014 :  08:55:51 AM  Show Profile  Visit willism's Homepage  Reply with Quote
Our air ride w/c ic's do the same thing the air ride is raised all the way up cause of the poor clearance on the tires and its top heavy with the w/c.... they leak all the time.
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beserkur
New Member

9 Posts

Posted - 10/02/2014 :  8:32:53 PM  Show Profile  Visit beserkur's Homepage  Reply with Quote
Sounds like a faulty purge valve-I've done road service for 20 years and it's my experience that an air dryer that constantly purges has defective purge valve-I have also rebuilt several in the past when the kits were affordable and worth it to rebuild-also a really clogged/blocked cartridge will have the same effect,but you say it's only a year old so I doubt it's blocked.
BTW the cartridge should be replaced every two years,max(although I suspect it will be cheaper to replace the complete dryer)
Keep your governor-it is still good.
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beserkur
New Member

9 Posts

Posted - 10/02/2014 :  8:35:58 PM  Show Profile  Visit beserkur's Homepage  Reply with Quote
quote:
Originally posted by buster133

Now I have the same problem on the sister bus. So far Iíve replaced the ľĒ line from the compressor to the air dryer, replaced the AD-9 with a rebuilt and replaced the governor. The problems went away for about two weeks, and then constant purging problem returned, went away for half a day and now is back purging itself just about every ten seconds while the bus is running. Iíve checked all the lines I can see underneath with soapy water, and when the bus is off there is no detectable leaking sounds and no loss of pressure over night.

This bus also requires a parked regen about once a week because itís only used in town and does a lot of idling when loading and unloading wheelchairs, not sure if that relates or not. Anyone have any ideas? Canít afford to tie it up @ the dealer since itís my only 3 W/C bus!




It's a rebuilt Dryer? Replace the purge valve-it can be faulty and happens alot. cheap to try and I'm sure it's the culprit.
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beserkur
New Member

9 Posts

Posted - 10/02/2014 :  8:38:20 PM  Show Profile  Visit beserkur's Homepage  Reply with Quote
quote:
Originally posted by beserkur

quote:
Originally posted by buster133

Now I have the same problem on the sister bus. So far Iíve replaced the ľĒ line from the compressor to the air dryer, replaced the AD-9 with a rebuilt and replaced the governor. The problems went away for about two weeks, and then constant purging problem returned, went away for half a day and now is back purging itself just about every ten seconds while the bus is running. Iíve checked all the lines I can see underneath with soapy water, and when the bus is off there is no detectable leaking sounds and no loss of pressure over night.

This bus also requires a parked regen about once a week because itís only used in town and does a lot of idling when loading and unloading wheelchairs, not sure if that relates or not. Anyone have any ideas? Canít afford to tie it up @ the dealer since itís my only 3 W/C bus!




It's a rebuilt Dryer? Replace the purge valve-it can be faulty and happens alot. cheap to try and I'm sure it's the culprit.
your regen problem is not related in any way.

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buster133
Advanced Member

USA
414 Posts

Posted - 10/03/2014 :  10:21:13 AM  Show Profile  Reply with Quote
Replaced the purge valve today and the problem still exists.

[URL=http://s7.photobucket.com/user/buster133/media/6f2e0703-1970-4ac9-bb1f-b6b9d7c12297_zps1741e113.jpg.html][/URL]
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beserkur
New Member

9 Posts

Posted - 10/03/2014 :  9:16:49 PM  Show Profile  Visit beserkur's Homepage  Reply with Quote
[quote]Originally posted by buster133

Replaced the purge valve today and the problem still exists.
[/quote
Ok...Inspect the check valve on the dryer,It is the fitting that goes to the air tanks.
If it does not close off, air keeps leaking back from the tank out the unloader, until pressure drops then the unloader kicks back in.
Also on the side of the dryer there is a half inch plug, take it out. Inside you will see a plastic X shaped pin, take it out. There is a spring attached to it. on the other end should be a small O ring.check it for wear etc..
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beserkur
New Member

9 Posts

Posted - 10/03/2014 :  9:21:12 PM  Show Profile  Visit beserkur's Homepage  Reply with Quote
Found this on Bendix site....
Dryer is constantly "cycling" or purging. Dryer purges frequently (every 4 minutes or less while vehicle is idling)
Excessive system leakage IMPORTANT: Note whether air pressure loss is shown on dash gauge(s). Pressure loss shown on gauges is caused by service brake system or component leakage. Pressure loss NOT SHOWN on gauges is caused by supply system or component leakage.
Leaking purge valve housing assembly and/or O-rings in air dryer end cover.
Holsetģ "E" type compressor - When installing a Bendix Drop-In air dryer in a system equipped with a Holset E or QE compressor, remove the Holset ECON valve along with its feedback and governor control line.
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