BIGDOG66 Posted December 29, 2011 Share Posted December 29, 2011 (edited) OK guys new here and now needing a little info. Got a 2000 mack 4 axle road tractor the other day going down the road it started purging every 7 seconds then quit for a few days then started back up. so replaced the governor didn't help so started looking into the air dryer and purge valve pulled it off and tore it down and the filter had come apart in the can cleaned everything up and first rebuilt the purge valve still same so replaced it got a little better but basically the same. only thing left is the unloader I think. litttle more info what it is doing is going down the road or sitting in the shop it will build pressure to 125 psi then purge but instead of closing off it will continue to leak air down until it gets to 110 psi then purge valve closes and starts building pressure again and starts the whole ordeal all over again any help would be appreciated Thanks ScooterPS I talked to a tech rep for the maker of the purge valve, when I disconnect the control line to dryer it stops purging so according to him the dryer is ok what else is there tried 2 governors Edited December 29, 2011 by BIGDOG66 Quote Link to comment https://www.bigmacktrucks.com/topic/22364-air-system-purging-too-much-from-the-dryer/ Share on other sites More sharing options...
MidniteMechanic Posted December 29, 2011 Share Posted December 29, 2011 Sounds like the check valve in the drier is leaking by. It is the fitting that goes to the air tanks. Quote Link to comment https://www.bigmacktrucks.com/topic/22364-air-system-purging-too-much-from-the-dryer/#findComment-95806 Share on other sites More sharing options...
BIGDOG66 Posted December 29, 2011 Author Share Posted December 29, 2011 thanks but that was checked too actually it was the unloader in the compressor got a rebuild kit ordered be in tomarrow Quote Link to comment https://www.bigmacktrucks.com/topic/22364-air-system-purging-too-much-from-the-dryer/#findComment-95921 Share on other sites More sharing options...
Rob Posted December 29, 2011 Share Posted December 29, 2011 thanks but that was checked too actually it was the unloader in the compressor got a rebuild kit ordered be in tomarrowMidland compressor?Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/22364-air-system-purging-too-much-from-the-dryer/#findComment-95923 Share on other sites More sharing options...
BIGDOG66 Posted January 22, 2012 Author Share Posted January 22, 2012 bendix compressor still having issues have replaced the following componants compressordryerpurge valvegovernor has no audible air leaks this even has the Mack techs in Richmond Va scratching their heads, I have replaced every major component and it stll wants to build up to 130 psi then purge until psi drops to 110 or so then the purge valve shuts off and the cycle repeats. one note if I pull the feed line from the governor to purge valve it will stop purging any ideas what going on with this? thanks for any input Quote Link to comment https://www.bigmacktrucks.com/topic/22364-air-system-purging-too-much-from-the-dryer/#findComment-99108 Share on other sites More sharing options...
miro Posted January 22, 2012 Share Posted January 22, 2012 It still sounds like the check valve from the dryer to the tank. 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. Does not sound like you have tried that one yet. Quote Link to comment https://www.bigmacktrucks.com/topic/22364-air-system-purging-too-much-from-the-dryer/#findComment-99128 Share on other sites More sharing options...
BIGDOG66 Posted January 22, 2012 Author Share Posted January 22, 2012 thanks I'll check it out Quote Link to comment https://www.bigmacktrucks.com/topic/22364-air-system-purging-too-much-from-the-dryer/#findComment-99152 Share on other sites More sharing options...
MACKTRUCKS4 Posted January 22, 2012 Share Posted January 22, 2012 Check the air line you pulled and make sure it is not bloked with something from when the filter came apart. Blow air through the line in both directions. Quote Live every day like it's your last, because one of these days, it will be. Link to comment https://www.bigmacktrucks.com/topic/22364-air-system-purging-too-much-from-the-dryer/#findComment-99166 Share on other sites More sharing options...
alwaysmack Posted January 26, 2012 Share Posted January 26, 2012 I had the same problem with the AD9. 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. Mine was gone. Replace this O ring . Problem solved. PS I couldn't find one so I made one. from a rubber washer. Quote Link to comment https://www.bigmacktrucks.com/topic/22364-air-system-purging-too-much-from-the-dryer/#findComment-99740 Share on other sites More sharing options...
ProStarBrakes Posted May 13, 2014 Share Posted May 13, 2014 (edited) I been driving a 2012 Cascadia for about 3 months now, and it leaks air out a thin air line (pressure release valve?) under the motor every 10 to 15 seconds. Wasn't doing it until a few days ago. Company shop says it's normal. They claim to have serviced it with a kit of some sort anyway (doubt it). It got louder, so I called maintenance dept. and they didn't seem to think it was an issue. WTF? I know the damn compressor's got to be overworking itself. It doesn't "woosh" like it's supposed to, it just bleeds out the governor or whatever that line is. Anyway, sounds like the same thing this guy is talking about. I've read some stories online, and haven't really found a real solution. Doesn't seem like the problem ever gets fixed, or maybe it isn't a problem, but rather a condition in with some air dryers decide to work under out of the blue.I know what started it with mine though. I hooked to this trailer the other day, and immediately after, this started going on. So i checked to see if there was a blow out valve (or air release valve) on the air tank under the trailer, and it was, I bleed it for a good couple minutes while it blew water and rust. So that got into the trucks air system for sure, as the tank on it bleeds rust residue now sometimes. I also tried plugging the little air vent line where the thing keeps purging the air out of for a sec and water started draining out the bottom of the air dryer, so i quickly unplugged the line before i fucked it up. Didn't have a clue what I was doing, but there was a thread online that recommended something similar to force the diaphragm to the blow off valve to close or whatever.Just giving my story for the record. Going to have a company shop look at it again when they route me past one again. I don't care what they say, it ain't supposed to be doing that. It's just too loud, and there's got to be a reason why it doesn't "whoosh" like all the other trucks do.The mechanic and the guy at the office both say it's supposed to purge after it gets to 125 psi. Well no fuckin' shit, but why would the compressor constantly be running when the tanks are full, or why would it keep cycling? Edited May 13, 2014 by ProStarBrakes Quote Link to comment https://www.bigmacktrucks.com/topic/22364-air-system-purging-too-much-from-the-dryer/#findComment-245208 Share on other sites More sharing options...
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