Air Dryer Purging when Engine if Off

[flyboy013]

I was doing some maintenance today and decided to look at the air dryer issue a bit more. What I found was that after the air dryer purges the valve is slow to fully close. A small (compared to the purge) but constant air flow is expelled for an additional 15 seconds. After another 2 minutes (give or take 30 seconds), the air dryer would expel more air for about 15 seconds. It's not a high psi purge, but a constantly flow just like what occurs after the purge. Two minutes later this would occur again, but this time is would only last for about 10 seconds due to the air compressor kicking in. As @Chargerman suggested, it's probably the purge valve.

I've contacted Spartan to see about getting this taken care of under warranty (it expires tomorrow). I already have a service appointment scheduled to get the tone ring on my driver's side tag axle replace due to an ABS fault.

 

[Chargerman]

Considering that you are about to be out of warranty I would make a recording of it happening and make record of the date on it and also mention that you called Spartan about it on this day just in case there is an issue with them covering it although I suspect they will not give you a hard time

Good luck and let us know how you make out.

 

[flyboy013]

Funny thing is that Spartan already replaced the air dryer once ... while we were at the Spartan Academy in September 2018. They did their inspection and determined that it needed to be replaced. To the best of my knowledge, it was working just fine at that time, but I suspect there was some systemic issue.

 

[flyboy013]

I took the coach in for service on Friday. Spartan had agreed to replace the air dryer under warranty and had shipped the replacement part to them. The air dryer has been replaced and all is good.

The other issue that I was there to have taken care of was my ABS fault. I'm still in discussions (to put it nicely) with Spartan as to whether they are paying for a replacement tone ring as I'm told that the one on the vehicle is bent.

 

[NWIP]

Thanks for the follow up always good to hear of problems resolved. I hope you get a good resolution on the ABS fault.

 

[Chuggs]

I read your thread and you were on the right track. I don't know the model you have...but they generally work the same way. To purge, there needs to be air. With the compressor not running or running but unloaded...[ie at cut-out pressure and not bled down to cut-in pressure]. Once the purge has happened at cut-out...it should exhaust all of the air held in the cartridge body and purge tank either external or internal. No more air should be available. If the purge valve leaks air after about 30 seconds...the air could be backing up thru the discharge check valve, most likely, as you eluded to. (inside the port that the line to your wet tank connection is screwed into,,, Port 2.1 on a lot of dryers). The check valve and likely the system hasn't bled down to cut-in pressure yet...thus holding the purge valve open. But...there are other locations that might need attention. Your governors interntal o-rings or the inlet/exhaust seal could be fouled. The air could seep from the turbo cutout valve if it's stuck, exhaust port on governor. So, at some point, you kinda have fo verify where on the system the air is actually escaping. It's helpful to know...does the Purge valve start leaking when your tanks are empty, and the compressor first starts running and you has not reached cut-out pressure? Or does it happen only after cut-out but before cut-in? Etc...

It's a simple but complex little device.

I had one leaking at the purge valve on startup. Purge valve for sure... yeah, no...I took the purge valve out, examined it, and reinstalled it with new lube. Twice to no avail. Still lets air out. I put a new air dryer on the coach, because we didnt have time to kill. Now, at home, I cleaned and lubed the outlet check valve, governor, turbo cutout, purge valve...and tested it on the bench...adjusted governor cutout pressure...all works good on that unit again. You won't believe how gummed up these valves can get over time. Having a heavy duty set of split ring pliers, cleaning materials, lubricant...will generally fix the problem unless you find a bad component...o-ring, piston body or valve seat, spring, etc... but they sell little kits for all of these components. Wabco has blueprints of the different dryers they make. If you can read a pnuematic circuit diagram...it really helps understand the operation and pathways.