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Old 06-30-2019, 10:26 AM   #11
Mini-Skoolie
 
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Originally Posted by Brad_SwiftFur View Post
I can't think of many components in the air system that could both (A) cause a major air loss and (B) only do so intermittently.
Agreed. And may I add that an intermittently manifesting problem will almost always end up tracing back to some manner of foreign contamination which is interfering with otherwise functional components. The additional info provided by the OP makes me suspect the bus has an auto bleeder but debris has collected in the air reservoir and when it purges it prevents the valve from closing fully. I wouldn't think this alone could cause a catastrophic air loss but if the condition exists in one part of the air brake system then there is likely foreign matter throughout the system.
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Old 06-30-2019, 10:56 AM   #12
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Originally Posted by Sehnsucht View Post
Agreed. And may I add that an intermittently manifesting problem will almost always end up tracing back to some manner of foreign contamination which is interfering with otherwise functional components. The additional info provided by the OP makes me suspect the bus has an auto bleeder but debris has collected in the air reservoir and when it purges it prevents the valve from closing fully. I wouldn't think this alone could cause a catastrophic air loss but if the condition exists in one part of the air brake system then there is likely foreign matter throughout the system.

Having driven air brake equipped vehicles for well over 20 years (and worked on a few over the years as well), this has been my experience. The air dryer is the first thing in the system to get air from the compressor, before the air tanks, and as such it's supposed to remove the moisture and oil from the air before it enters the "wet" tank (it doesn't get *All* the moisture, especially once they age a bit). Many have filters/cartridges that are supposed to be replaced periodically (typically once a year in a daily-driver) but frequently it's neglected. Eventually the moisture laden oil makes its way past the filter/cartridge and gums up the auto-valve.
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Old 06-30-2019, 11:14 AM   #13
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Originally Posted by Brad_SwiftFur View Post
Not very helpful. Obviously something is wrong -
Bad brakes are no joke. .To operate a vehicle with known bad brakes is a criminal. Sorry Brad I guess your Mom doesn't have pins in her arm and her car totaled by someone who admitted in court that he knew his brakes were bad. Imagine for a minute a 30K lbs vehichle with bad brakes t boning you. No way should a vehicle with known defective brakes be in operation. Not to mention the liability issues.
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Old 06-30-2019, 11:45 AM   #14
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Bad brakes are no joke. .To operate a vehicle with known bad brakes is a criminal. Sorry Brad I guess your Mom doesn't have pins in her arm and her car totaled by someone who admitted in court that he knew his brakes were bad. Imagine for a minute a 30K lbs vehichle with bad brakes t boning you. No way should a vehicle with known defective brakes be in operation. Not to mention the liability issues.

I'm not disagreeing that defective brakes are Bad News and need fixed. As a professional truck driver, I've had a few over the years that I've put out of service because By Gosh if nothing else, I want to be able to stop safely - and for that matter, I want everyone else to be able to stop safely as well.



For the purpose of this thread, however, is not to determine "something is wrong", which I think is already reasonably well established at the first post. It's to determine what the problem is and to help the OP get a correct diagnosis to actually fix the problem, whether it's by fixing it himself or getting a professional mechanic involved. There's no point in blindly replacing parts in the hopes it will fix the issue.
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Old 06-30-2019, 12:18 PM   #15
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i have the same engine as the OP but mine is an 86 and his in an 89 and it doesnt have an air dryer or anything fancy not even an automatic purge valve.
belt driven compressor and the only purge valve is the manual tank drains.
thats for my bus 3 years older than the meyermobile.
so if it were me having this problem and an auto purge i never had before then i would suspect the manual drain purge valves as pointed out to have trash in them and pulled and replaced. But for meyermobile it sounds like he has an auto purge that has some trash in it or is wore out and might not hear it leaking while driving and it could be the governor is sticking and not quite shutting off at cut out pressure and once it does close it is sticking when its time to open and not regulating like it should so maybe the purge valve is fine?
just some idea,s
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Old 06-30-2019, 02:10 PM   #16
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Thank you Jolly Roger for that insight into this particular model. Without an air dryer sounds even more likely to be debris, either ingested solid particles or years of moisture rotting away the tank interior meaning the debris is actually rust flakes. If this is the case I regret to say the OP has a much larger issue on their hands. I'm not scolding here but reminding that these are not vehicles like your Honda Accord that you can just gas up, change the oil, and go - diesel engines and air brake systems do require a minimal amount of attention and respect or they will let you down at the most inopportune time. It is one of the reasons that warnings like what the OP experienced are important because the responsibility of driving a heavy vehicle such as these is greater than is sometimes emphasized here. We grow comfortable and therefore complacent, expecting the safeties and backup systems to always be there until they fail us. I'm glad the OP didn't experience a catastrophe and I hope the problem isn't as severe as I have theorized, but I also hope this reminds us all not to take for granted the duty we all have to mind our rigs are in top working condition before we hit the road each day. Maybe I and Brad Swiftfur and I know others on this forum who are also truck drivers are burdened with the knowledge and perhaps memories of what happens when drivers don't respect their rigs and the gruesome consequences. I'll step off the soapbox now.
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Old 06-30-2019, 02:29 PM   #17
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Thanks Brad,

I think it's the air Purge that is not closing completely, or is delaying.

There is a leak near the pump. Going to investigate that today and spray like crazy to find that leak! This could be linked to the intermittent governor failure.

I'll send some pics and story on my next update.
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Old 07-06-2019, 03:11 PM   #18
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Originally Posted by Sehnsucht View Post
Did it pass the 4 point air brake safety check during the pre-trip inspection?
No one does that.

And next to checking the slack adjuster for correct play it IS the most critical thing to do.
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Old 07-06-2019, 08:19 PM   #19
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Exactly! Your messing with death. Yours or some other innocent people. Tow it to a truck repair shop. Airbrakes require responsibility. Soapy water spray every connection when it bubbles you’ve found a leak.
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Old 07-06-2019, 09:54 PM   #20
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Originally Posted by Rivetboy View Post
The real truth is you do not know anything about air brakes and now they are in emergency failure mode you pull over and the e brake locks!!Tow that bus and spend some money to have the brakes fixed !!!!!!!!!!!!!!!!!!!!!before tragedy happens as I see it you have had 2 warnings....
WOW. “Emergency failure mode” ??!
I never heard that term before.

You know it sounds like his brakes work just fine. (Sounds like safety features built into modern air brake work as well) His problem is intermittent air supply.
It seems he has a quite large air leak one moment . And no leak (or one much smaller) the next.

That sounds like a prime candidate for sticking dryer valve. At least that is where I start looking.
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