air dryer leaking, now another problem, (solved finally)

[David Anderson]

I needed to bring this back up to the top.  See post number 5.

David


I am on a trip and my AD-2 air dryer is getting to about 110 lbs then leaking out the purge valve.  I can put my hand under it and hold the pressure and when it gets to about 115 it makes a purge attempt then continues to leak out the exhaust.  The compressor and unloader are new and everything worked ok on the last trip.  This is a new problem.  I'm parked in Glenrose TX for two weeks and would like ideas on what to look at.  The eagle manual doesn't give any details on the purge valve other than a cut away view.  I'm due for a cartridge replacement, but I don't know if that will solve the leaking problem.  Where are there a close truck parts outlet near Glenrose?  I'll be away from the computer for a few days, so my response will be slow.

David

[luvrbus]

David, any good size NAPA store can get AD-2 repair kits for you over night that is where I buy mine



good luck

[DaveG]

Yep, rebuilt it (bottom only...unless it has been awhile then change the cartridge too). The kit and cartridge both have instructions in their boxes, so look it over and if it is too much for you find a truck repair shop that can do it for you. Probably only a couple of hours, maybe an hour depending on location, etc.

[buswarrior]

Like they said, a new bottom on it and you are done!

Good opportunity to check the heater wire for power.

happy coaching!
buswarrior

[David Anderson]

Well I'm finally back home.  I went ahead and bought a whole new dryer.  I had to get it at Truck Ag and Auto in Stephenville 254-965-6080.  They didn't have the kit and were out of AD-9 dryers.  I bought a Meritor Wabco 1200 series dryer.  It is a lot smaller than the AD-2.  I've got enough room in there to install hydrolic levelers, now.  I had to buy a couple of plumbing fittings to rig this to get home.  I'll get the right parts next week now that I'm back.

I was in a real pickle on time because of the job I was on.  I guess I could have chanced an order and waited to get the parts, but I would have had to drive back to Stephenville to get them.  That AD-2 was 25 years old.  I guess the bus deserved a new one after that long.

Thanks for your help, Clifford.

David

[David Anderson]

I finally got the proper fittings on this and did away with the plumbing fittings.  I ran a test and the dryer purges at 120 but cuts back in at 118psi.  It should cut in at about 95.  The governor was replaced with the compressor back in December.  I now wonder if I have a bad governor?.  

I pulled the output line on the dryer to make sure the new check valve at the wet tank was properly installed.  It worked correctly.  I then pulled the governor line (line 110 in the picture) and as the bus compressor approached 120psi the governor line pressurized the line to Port C on the air dryer as depicted in the picture below.  I stuck it into the dryer connector (port C) and the dryer purged.  Then after a few seconds the governor line (110) air flow stopped and the compressor began to load the dryer again.  I repeated a few times with the same results. 

In the picture I assume line 9 from the Wet tank pressurizes the reservoir port on the D2.  It should have pressure at all times equal to the pressure in the wet tank but must achieve 120psi to engage the valve D2 to send air down line 110.  I also assume it maintains enough spring pressure on the D2 to keep the compressor unloaded until about 95psi (cut in)

What am I doing wrong here?  You think I have a bad D2 valve out of the box??

David

[Dreamscape]

David,

Check out these, much better than I can explain.

http://www.bendixvrc.com/itemDisplay.asp?documentID=4842

http://ww2.justanswer.com/uploads/Budnshe/2009-08-21_042015_a1302050wm.pdf

http://www.tpub.com/content/waterstorage/TM-5-3820-256-24-4/css/TM-5-3820-256-24-4_140.htm

Paul

[David Anderson]

Wow, what a day.  I spent the whole day trying to find out why I had this problem.  I had the governor bench checked.  It was good.  I called Meritor.  They said it was an unloader problem.  I called Bendix.  They said I had a leak.  I disconnected lines on the dryer, plugged lines where they told me, checked for leaks.  Finally the tech at Bendix said put a pressure gauge on the reservoir port and see if it drops a bunch on a purge.  I revved the bus up with fast idle and watched the gauge.  Poof, it dropped 30psi immediately after the purge.  Ok where is the leak?.  I turned off the fast idle and let it purge and no drop.  

Darn, the leak was in the fast idle valve.  Well I can't hear that leaking with the engine running, and didn't think to turn it on with the engine off, duh.  A whole day searching this gremlin.  I buttoned everything up and called it a day,  5:15pm.  Man, this was frustrating, but the system is fine sans the fast idle.

I'm glad this problem is over with.

David