PURest Air Dryer constantly purging/leaking

[Awesomeness]

I have the newer style "PURest" air dryer, and it just started leaking out the purge exhaust valve. The air compressor is to outrun the leak, and keep the tanks full, when above idle. Does anyone have experience with what causes this and how to repair it?

I tried googling, but didn't find much, besides this: https://moistureboss.com/blog/air-dryer-constantly-purging-a-few-troubleshooting-tips/

Do you think this "PURest® Air Dryer Major Repair Kit (DQ6053)" would fix it? Instruction manual attached.

I have 2 days to fix this.

 

[Ronmar]

What happens when you disconnect the purge airline off of the bottom of the dryer? When the governor reaches pressure and unloads, it sends system/sense pressure down that line to open the dryer purge valve so it can back-flush the coalescing media with air stored inside the dryer housing. If you are getting air out of the purge line constantly, and not just when the governor unloads, then you have a governor issue up at the compressor.

If you remove that line and no air comes out of it until the compressor unloads, but the dryer continues to purge, something is up with the purge valve on the dryer. You should be able to remove the valve assembly and clean and inspect it... Could just have some crap in it...

 

[Awesomeness]

The air is leaking out of the "purge exhaust cover". Where is there a "purge airline" to disconnect?

 

[Ronmar]

There should be 3 lines attached to the dryer. Main airline in from the compressor, dry air out to the wet tank and a third small airline should connect near the purge port/cover. that line runs up to the governor. On the old style units it is a 1/4” line and it connects right up into the bottom of the unit where the purge valve is. On these, the control port appears to be opposite the inlet port, right next to the purge valve cover(toward the rear of the truck when mounted?) seen in this bottom view.

so I would pull that line, start the truck and see if air comes out constantly, or if the purge valve leaks constantly. That will tell you which way you need to go... once disconnected, I would secure that control line to something with line or a zip tie as it might want to start whipping around once air starts coming out of it, especially once the compressor unloads

 

[Awesomeness]

Thanks, I think I understand what you're saying. I'll check it tomorrow morning.

 

[Floridianson]

Forget what model but check valve can cause that. Something about air up the system shut down truck remove the pressure line off compressor or dryer see if air dryer is leaking air from the wet tank back through the air dryer. If it is compressor unloader is staying open because of that back pressure. Just guessing as so far no problems with mine to have to find check valve. Believe you can just clean it.

 

[simp5782]

Pure air plus and purest air units are notorious for sticking the purge valve open after a purge and you simply tap it back in with a hammer and screwdriver.. sometimes it corrects itself other times its a purge rebuild.

 

[Awesomeness]

Pure air plus and purest air units are notorious for sticking the purge valve open after a purge and you simply tap it back in with a hammer and screwdriver.. sometimes it corrects itself other times its a purge rebuild.

Stick a tool/screwdriver straight up in the exhaust port, and tap?

 

[simp5782]

Stick a tool/screwdriver straight up in the exhaust port, and tap?

Yes

 

[Floridianson]

Problem with that is if not cleaned or fixed it will just happen again. Wonder if some Cat compressors just spit out more junk than others. I have not had any problems with mine but I have no hours on it. Sold the truck just waiting for the man to transfer title before I let it out of my yard.

 

[Ronmar]

Or something else in the system broke down and provided crap. Took apart an old style dryer last week that was full of brass shavings from input port down to the filter. The filter/media should however keep that from getting to the purge valve.

If it is a stuck purge valve, Maybe you got a mud dauber trying to nest up in the purge port...

 

[Awesomeness]

Just got done messing with it, Round 1.

• The air dryer leaks out the purge valve lightly, until the compressor sends pressure down the control line, then it dumps and stops leaking.
• Without the control line attached, the purge valve leaks lightly continuously. Never stops.
• I took apart the purge valve, cleaned it, and regreased it. Everything in there looked fine, except this curious bit of (spring?) wire. The ends of the wire are not shiny/fresh, so it's been there a while. I don't see anywhere on the purge valve that this wire could be from, and the springs on the purge valve using a thicker diameter zinc-plated (shiny) wire. Looking up inside the purge piston bore, I don't see anywhere the wire could have come from, nor any passageways large enough to let it pass (because of its curved shape).
• After putting the purge valve back together, there is no change in behavior. It still leaks, lightly.

 

[Ronmar]

Assuming there is some sort of spring that holds the purge valve closed? Is it intact? That metal may have come from a spring coil?

Failing that, the wire may have scratched/damaged a surface or the o-ring that it should seal against. As long as you are sure there is no air leaking down the control line/it is disconnected, there is something up with that valve...

 

[Awesomeness]

Assuming there is some sort of spring that holds the purge valve closed? Is it intact? That metal may have come from a spring coil?

Failing that, the wire may have scratched/damaged a surface or the o-ring that it should seal against. As long as you are sure there is no air leaking down the control line/it is disconnected, there is something up with that valve...

The purge valve does have a spring that holds it closed, but this wire couldn't be from it. The spring wire is thicker diameter, and zinc-plated. I can't see anywhere this could have come from, and it's pretty corroded, so it's been there a long time. I checked all the o-rings on the valve carefully, no nicks or cuts. Also nothing I could see in the mating faces on the valve, where I thought the wire could have gotten lodged.

 

[frank8003]

It is broke. Now get one of those 17 guys in the motor pool to fix it.
They got all the latest TM and an endless supply of parts..................
In our military, They don't do conjecture, They just fix it.
Tactical military vehicles were built and do a jobs and save our lives.

 

[Ronmar]

It is broke. Now get one of those 17 guys in the motor pool to fix it.
They got all the latest TM and an endless supply of parts..................
In our military, They don't do conjecture, They just fix it.
Tactical military vehicles were built and do a jobs and save our lives.

Unless of course they are the knuckleheads(or knuckledragers) who broke it in the first place

 

[Awesomeness]

I replaced the purge valve, using the DQ6053 kit, and now it's fine.

Haldex DQ6053 Air Brake Dryer Valve Kit + Cross Reference | FinditParts

Haldex DQ6053 Air Brake Dryer Repair Kit - Lower Housing Repair Kit, For use with PURest™ Air Brake Dryer ✓ Order now for same-day shipping on eligible purchases from FinditParts.com, America's online marketplace for heavy duty parts.

www.finditparts.com

 

[vvwilkins]

I replaced the purge valve, using the DQ6053 kit, and now it's fine.

Haldex DQ6053 Air Brake Dryer Valve Kit + Cross Reference | FinditParts

Haldex DQ6053 Air Brake Dryer Repair Kit - Lower Housing Repair Kit, For use with PURest™ Air Brake Dryer ✓ Order now for same-day shipping on eligible purchases from FinditParts.com, America's online marketplace for heavy duty parts.

www.finditparts.com

This past weekend I resolved a similar problem; however, replacing just the purge valve was insufficient. Required replacement of the "Turbo-Saver" valve due to debris (and age) keeping it from seating sufficiently. If the Turbo Saver valve does not seat correctly it will let air pressure build up in the purge value which will cause it to unseat and thus leak or cycle prematurely. I used the DQ6020 kit for the Air Dryer rebuild and replaced the Coalesce filter and Dessicant with kit DQ6036. Both kits sourced from Eriks Military Surplus. This thread was very helpful in triage and determining which coarse of action to take. Thanks to all the contributors.

-v

 

[Khann]

I am having the same issue with the air dryer purging about every 30 sec with the old style. I then read through the TM and it said replace the air governor because when I take the control line off I feel air coming through (when line is off no purge) so I Put a new governor on with no change and since i want to upgrade to the newer style like yours. I installed the Haldex PURest air dryer today and I still have the same issue. so after soaking all connections with soapy water everything showed tight but still have the issue.

Could the new Governor be bad because I still feel air coming out of the control line when unhooked?

Other possible issue in my haste to beat the incoming rain I switched the main line form the governor with the wet tank link so basically running air backwards through the dryer I notice this mistake after about 45 sec of no air pressure building on the gauge. do I need to rebuild the purge valve thinking messed something up internally.

any support apricated
sorry to drag up an old post but it appeared to be closest to what I am experiencing

 

[GeneralDisorder]

You really should start a new post - your issue is likely that you are losing pressure in the wet tank and the compressor is cycling on and then purging. A reasonable sized leak will dump enough pressure to load the compressor every 30 seconds or so. It only has to drop below 95 psi to cycle the compressor on and cause a purge. Put a gauge in the wet tank and watch the pressure.