[BusNit]

No joy on airing it up from the rear. Would CoachNet send a mobile guy over? I've been trying to figure out how this air system is plumbed and what/where whatever is keeping the air from reaching the front brake tank.

[Richard]

Air flows from the engine compressor to the Wet Tank. We know that is working because your supply pressure comes up. The air then flows to the brake tanks via the PPV. You have replaced it so you know where it is.

A small guy like me can crawl between the tags and access under the coach area.

I am very curious about something. When you tried the reboot of the air system by letting all the pressure out, did you pump the brakes and bring the secondary tank to zero? If so, did it rebuild to 120?

To the best of my knowledge there is only one PPV. So if the secondary tank built back to 120 after releasing then the PPV is working. There may be a check valve between the PPV and the brake tank. That is a big maybe.

How are your brake tanks drained? Auto, toggle pull, valved to exterior.? When you hook the coach to shop air, can you hear air escaping?

You have used the word the primary tanks builds lazily? Can you clarify? I was under the impression that it wouldn’t build any pressure. But if it builds any pressure, it is not likely the PPV. If it builds pressure, does it lose the pressure when you stop the engine?

Sorry for all the questions, I am trying to noodle out the diagnostic in public.

[BusNit]

I did pump the pedal to eliminate all air. I went under the coach yesterday to ensure for the 6th time I had the lines correct. (Front tanks) There are only two 1/2" lines that could possibly be crossed but I "crossed" them to test with the same result. I put them back afterwards. The remaining lines have a specific port based on size of tubing. Front two tanks have manual air drains that I relocated to exterior. Rear tank has auto drain. I do know the aux tank gets air and the brake tank does not. The work lazy was my sarcastic comment on the coach not wanting to be moved and thus not airing up. Both single (front) are brake needle and aux gauge needle hold air for a couple days at least.

After all air was dumped one half of air brake system (White needle did build air as did the aux tank to 120.

Last night I had an epiphany and this morning I got a text from Glen as if to confirm my epiphany. I will plumb in a Milton air hose chuck, a valve for secondary safety which will go to the exterior next to front tank drains. This air chuck will allow me to fill via external compressor the brake tank that is not getting air and hopefully at the very least allow me to move the coach forwards.

With that done I am speculating that somewhere at the back a check valve either failed or a small animal got up there and misadvertantly stepped on the lever valves next to the PPV thereby cutting off air flow. (Fat chance but it is something worth looking at) We do have paw prints all over the property from foxes, coyotes, rabbits, cats and stray chickens.

My goal is to pull the coach up and rebuild the back half components. I hope this works.


Lesson learned?... Build a full length pit on the next one. Also this all did work fine (Air brakes worked and pressure on rear built up) after everything went back together last month.

Final thoughts. I am fairly small too but I have the steel tubing welded between tag and drive axles for a secondary mud flap which hinders access.

By the way, Thank you for responding as any ideas really help!!

[Richard]

Brilliant idea on plumbing in an air chuck to the external drain. Brilliant !!!!!!

Btw, as a quick sanity check, all you have to do is connect the drains from the two tanks and open the valves. If you used tubing for the drains, one double ended push on connector and you will know.

And if it doesn’t air up, you have traced the problem to the tank itself.

I can’t keep up with all you do. Did you refurb those two tanks? And if you did, did you happen to treat the inside with anything? And is the inlet on the bottom? I know, I know, it’s far fetched. Unicorns not even zebras.

[BusNit]

I could cap off with a push on plug the 1/4” drain and open both valves but I’m thinking if this happens on the road a service port to the tanks might make quick work.

Both tanks have been cleaned and powder coated. Interior has been sloshed with rust inhibitor coating. (Red material that they use on steel building purlins)

All this did work fine but I let the coach sit un-aired for weeks after I tested it all. There are new check valves on both front air tanks as well as protection valve. (All Bendix brand) all inlets are top side. Drains at bottom and new service port will go on unused 3/8” side tank port.

[BusNit]

Success!  I added a Milton air chuck as a service port to the brake tank up front. Since the only access I had was to the front air tank (Side plugged port), this only made sense. The chuck is in the front a/c compartment along with the two front air tank drains. I also put in a valve as added measure to ensure brake air stays where it needs to be. My little compressor filled it up fairly quickly along with the onboard compressor. Around 90psi on the service gauge, the aux began to fill so I know that check valve is good and possibly the one up front that I already replaced. I haven't started the coach and will do so tomorrow. What I did do is release the brakes and she took a stroll back a few inches before I engaged the parking brakes again. At least I know that part is good. She was happy to roll back that 4" but not as happy as I. The  compact external compressor brought up the pressure to 130 and the onboard compressor went up to 100 where it cuts off. At least there is another service port direct to the brake system if it ever needs to be. Also glad to know the small Milwaukee compressor was able to do its magic. It was more of a test bed since I really didn't feel like unreeling 120' of air hose from the garage to the bus.