Does anyone recognize this Air Valve? Located on air tank

[Mike Shumack]

In the hunt for air leaks, I found this valve, located on the air tank, leaking.

Does anyone know what brand it is (who made it)?

I'm assuming it is a "safety protection" valve. Maybe an adjustable valve? It has "04" stamped on the top.

But I've never seen one like this.

Why the knurled knob? It does not appear to do anything when turned.

[David T. Richelderfer]

I found this after using "adjustable brass air pressure release vent valves" as the search argument in Google.  It's close but not identical.

https://www.google.com/shopping/product/1362377906036398819?rlz=1C1QJDA_enUS634US634&biw=1920&bih=937&sxsrf=ACYBGNTyICrKXLT--LOLxlmQV_842qe2ww:1577454683136&q=types+of+adjustable+brass+air+pressure+release+vent+valves&oq=types+of+adjustable+brass+air+pressure+release+vent+valves&prds=epd:11494842605918698069,paur:ClkAsKraX4LtriywnpDwIhFWU5j4KGViYwVioExWyIGirlwdhrJdtnd66hUszD7__tKBG-VIatTaPI1aZjnfd8reQwBFM0vrttIi3vQ2siDIsAFJj0DP4nrKERIZAFPVH71Sq0T4r4lrlCta6CjGd8x_E1jxlw,prmr:1&sa=X&ved=0ahUKEwiMnZve_NXmAhUWJTQIHcliB_sQ8wII9AM

[Mike Shumack]

That looks close.
I would think it is adjustable since it has the knurled knob. But it doesn't seem to do anything. I suppose if you get one that is adjustable you would need to set the relief pressure on your work bench with air pressure connected and a gauge, else you would not know what the setting was by just turning the knob.

I tried to remove the screw at the end (for inspection and cleaning) but it broke off of course.

I'm just going to replace it with a Bendix ST3 safety valve with 150 psi relief setting. My air system should not be getting over 150 so that should suffice. They also make a 175 psi relief.

[Chuck Jackson]

It looks like the knob is attached to the spring, Rather than turn it, can you pull it?

[Mike Shumack]

I already broke it.
I could not pull it. The spring is stiff. I tried to take it apart.

On the bottom you can see the spring and a hex head retaining bolt. I tried to unscrew the hex and the bolt broke.
It looks like the bolt they used to retain the spring was about the thickness of a human hair.
I think the knob was there to turn the valve every so often to clear the seat. The top of the fitting has a concave seat and the knob part has a rubber seat.

[Mike Shumack]

Does anyone know if the "dual air tanks" used by the Patriot and Marquis (the SMC Magnum D-series chassis) have an "internal check valve". These tanks (both in photo) are dual, you can see the weld seam to the right of center). Some dual tanks used an internal one-way check and some just plumb the air lines external.
I'm not sure what style SMC-Beaver used. My primary and secondary air systems are bleeding down together. I'm trying to locate a Shuttle/check valve.

A chassis air system diagram would be very useful.

[Lee Welbanks]

Mike, I have the same little valve in one of my front air tanks, it doesn't leak so I haven't messed with it. I almost looks like a bleed valve like the put on compressor tanks, I'll check it out and let ya know when I get back to putting the HWH manifold back together.

[Mike Shumack]

My chassis has three air tanks. I'm trying to figure out where the "primary" and "secondary" air systems tie together.

Usually "trucks" have a shuttle valve which provides air to some item from both air systems (like a tee fitting) but if one system loses pressure, the shuttle valve slides over and blocks that port while continuing to supply air from the side with the higher pressure. So one system/side can be out of air and the other side would still hold air. But if the shuttle valve sticks, it can let both sides drain out together. i think that is what is going on wit my coach - as both air sides are draining equally fast.

An Air System schematic for a SMC Magnum D-series (blue Diamond) chassis would be very helpful, bit I don't think such schematic exists. I have some for the Roadmaster chassis.

This is a photo of the two stacked tanks, and the rear tank. I believe I know where all the lines going to the rear go. Now I need to trace the lines going forward.

[Lee Welbanks]

Mike, It would be really sweet if they would supply a "as built" drawing or book with these coaches, I have all of the original paperwork and books that came with my 06 PT even the complete electrical book, but even it is not a as built. I've found a bunch of electrical things that are different from the book. And other items that are not even in the book.
I would pretty much bet money that there are not two coaches built alike.

[LaMonte Monnell]

Lee, I think every coach is different to some degree. All depending on which technician or helper was running wires,hoses, or cables etc. on a particular day.
All the years I spent rebuilding aircraft we pretty much did it all"by the book" except for a few small changes here and there.

[Mike Shumack]

I have determined that both the "stacked air tanks" have internal check valves that separate the wet and dry sides. I'm going to try to remove them and clean (I doubt there are any replacement available).

[Lee Welbanks]

LaMonte, I would just love to get the guys that installed the HWH leveling manifolds up in the chassic with all of the valve connections in a plastic bag zip tied to whatever was handy.

Mike, Why do you think you need to clean the air tanks, do you get a lot of water out of the drains? I have never gotten any water out of any of my drains and also working on all of the air leveling manifolds have I ever noticed any moisture. Dry as a bone.

[Mike Shumack]

I tested the internal check valve in the tank (aired up tanks, drained Wet side, then removed the feed hose to wet side and some air was seeping out). so I know the internal check valve is leaking a little. However that is an internal leak, and need to focus on external leaks, so I think I will skip the removal/cleaning of those check valves and move on with my leak finding.
At least I know more now about this air system. I have traced all the large 5/8" air lines and checked them for leaks.

I did find two leaks in the rear. One is the line into the Relay valve, and the other is at the solenoid for the Tag Axle dump/lift.
I don't think I will do anything about the Tag solenoid ( I think the only fix for that leak is to replace it - and it looks to be expensive).

[Stan Simpson]

I am just amazed at the pictures you post here, Mike. Not just this group but others. How the heck do you get to this stuff? Just amazing!

[Lee Welbanks]

Mike, I assume you have the same HWH leveling system as my 06 PT, the solenoids have two O rings that seal them to the manifold, one inner and a outer, I've found a few of mine leaking but most are just fuzzer leaks. The O rings are easy to change out, just remove the electric solenoid form the valve and unscrew the unit. The O rings are not standard type they are really skinny and you can get them at most Ace or True valve hardware stores. Once I found the size I ordered buna N pieces. If you have Nason pressure switches they are probably leaking. They can be taken apart and cleaned and re-assembled, they leak form the inner diaphragm, tighten up with a 1/2" socket. Mine are set to 20 psi open, they are normally closed. Apply 20 psi+ air pressure to the valve then screw in the solenoid until the switch opens.
The air switches is where I've found most of my air leaks along with a few of the push to connect fittings. Right now I am replacing both front right side air bags that were leaking.