An Air Leak Question

I need help from the brain trust. My aux pump would go about 24 hours between cycles. I installed the shutoff valves in the converter manifold to my converter installed air devices such as pocket doors, bed lift, seat, generator air bags, drain valves, air horn etc. No change after installing the valves, but recently, as in the last month I am losing aux air. With those closed I am leaking down from 80 to about 40 overnight.

With those open I have virtually the same leakdown rate so I started looking for other leaks. The bus auxiliary air system has the air door lock, the front shutters, the belt tensioners, and of course the suspension.

I have ruled out the air shutter cylinder, the air door lock cylinder, and the aux air tank petcocks. I used the ultrasonic leak detector and soap on them and couldn't hear or see anything. No bubbles, no noise.

That leaves the belt tensioners, belt tensioner valve and regulator, and the solenoid valves in the suspension system. It also leaves the aux air into the norgren valves and I have not yet soaped or listened to those. They are on my list, but I lack confidence anything there is leaking. Those types of leaks tend to show up on the ultrasonic leak detector and I have waved it around all the valves and their respective fittings.

I have checked the compressor and all fittings from the compressor to the converter protection valve. If I have a check valve in that line I cannot see it.

What am I missing? Has anyone found leaks in the aux system that were not where they would be obvious? I know Mango had a leaky regulator on the passenger side near his transmission, but if I have one I cannot see it. and I cannot hear anything with my leak detector or stethoscope.

BTW, with all the valves I installed on the manifold the converter installed I soaped the hell out of it and that is not leaking. Also, If I turn off those valves, and then 24 hours later turn them back on one or two will give a slight hiss when opened to indicate the device they control does have some leakdown, but I cannot see a measurable difference in the air loss with the valves open or closed. Based on the sound of air moving through the valve I suspect they might leak a few bubbles but they are not bleeding off air.

In anticipation of anyone suggesting air bags or other parts of the suspension system there are two reasons I am not looking there. First, the bus will sit without leaning for a long time, and if it went to 40 PSI it would sure be leaning, but second, that air is trapped by the 5 port Norgrens and is isolated from aux system air.

How about a leak at the Aux air gauge in the dash?

Step slide air cylinder. Check both the shaft end and the air line connection. I think yours is easier to check than mine was. At least I hope it is. When my cylinder went south, it started out as a slow almost impossible to find leak and over time got so bad I had to turn the air off to the slide until I had time to replace it.

Check the various air needs of the drivers seat.
Concentrate on the lumbar support.

JIM

Jon, At Titusville we found a leak in Pete Petree's Belt Tensioner Valve above the doors. Easy to fix, hard to find.

We are all honored you have asked us for help !

Paul, My gauge is on the end of the mainfold. No leak there.

Ted, My step slide is in the converter side of things and I can turn off air to that. No change. Air still leaks even with the valve to it turned off so that is ruled out.

Jim C., Diver's seat, see response to Ted.

Jim K. I have gone over that with the sonic leak detector and stethoscope, but I do have to get out the bubble machine and see if that shows any thing. A one and a two.........

When I start considering how many fittings and components I have to check it makes me want to let it leak. I'm just glad it isn't in the pocket doors, which by the way are the only items on the regulated air supply line and this morning when the air in the aux system was down to 40 PSI, the pocket door air system was still holding at 60 PSI where it was the night before.

Check the flange for the diaphragm of the limit switch that controls the aux. compressor.

Check the norgren air filter water drain pet cock.

Did the drain valves, but not the diaphragm. If the diaphragm were leaking I suspect my compressor on and off points would change, they haven't, but I will look anyway.

I need Hector's bubbler.

Jon, maybe it would be easier to find the leak at higher pressure.

Induce shop air into the system at a higher pressure.

JIM

what about isolating the compressor with a ball valve, air up and turn off the valve and see if you loose air?
GregM

I like that idea Greg, I too was thinking the compressor might be leaking.

JIM

A1: When I owned a Liberty I had to tighten the fittings coming out of the compressor once a year. Even had to replace the fitting once. The leak would become quite severe at times. This is done thru the access panel forward of the front axle.

There is a regulator towards the rear of the coach from the house batteries and forward of the battery equalizers. Damn near impossible to see and almost that bad to get too. You can see it or feel it by going in with your hand from the rear over the chassis batteries. Never did know what it regulated but the line in would leak.

I have a brand new replacement for it if you need it

Thanks Roger, I think I just found my leak.

JIM

Jon:

I have been chasing aux air leaks now for 6 months. A couple of things that I have found which may or may not apply:

I found aux air fittings in places I would not have expected (e.g. plumbing bay). It looks like a couple of splices put in by a previous owner. Yep, one was leaking.

Also. I have found that some leaks change based on last use. for example: drive all day, only use air slide, aux air leaks down to 40 in about 4 hours after docking. Last trip, drive all day, cycle all house aux air systems at docking, aux air holding 60 in 24 hours. Narrowed this down to bed lift. So, drive all day, dock, cycle bed lift, aux air holds 60 in 24 hours.

I know that's not a fix, but I feel like it was a valid observation and has proven helpful. I am no longer threatening to shoot aux comp or aquairium pump as I refer to it.

Also, I found if I raised the preasure in a circuit about 10 lbs, it made leaks a little easier to find.

I'm with Jim K. The belt tensioner valve stumped me for a while. What I found was that the since the hole at the bottom of the valve is so large, it wouldn't soap up. Actually, Jim Shoen found this for me. I had soaped up all the usual suspects but couldn't find any bubbles. But when Jim put his finger over the hole, he felt pressure build up. I NEVER would have figured that one out. Maybe not your problem Jon, but for others, this was a tricky place to find a leak.

Good luck.

Adam

Adam I had that leak. I put in a new valve and it leaked the same. It was the tension cylinder that was bad that ended up being the culprit. In a pinch you can stop that leak and still maintain belt tension by turning that valve slightly till the leak stops.

The flange for the diaphragm for the regulator for that is also a good place to look for bubbles.

As soon as I can get under the bus I will get back at the leak chasing.

I aired up the system to 130 PSI hoping I would create some noise at the leak.

I am seriously considering the use of freon and a sniffer that someone previously suggested. With any luck if I can rig up the required fitting at least I should be able to get in the area of the leak(s).

Now I know why Roger traded.

BTW Roger......the first place I looked was behind the compressor cover plate because I remembered you had problems there.

A few more to check:

The air sewer dump valves. There are also connections up above the holding tank on mine where airlines are joined.

The aux compressor head, not just the lines.

I just surrendered and the aux pump runs about twice in a 24 hr period when the bus is not in use.

Except for dumping we don't even need aux air because we don't close the pocket doors or do anything else that needs air. It is just the idea that I have a leak(s) and want to find it.

If my bus ever gets wet it is going to look like a bubble machine with all the dried soap everywhere. At least it smells nice.

Hi Jon,
It would be hard for you to put more soapy water on your fittings than I have.
Yesterday I isolated the two small bellows that tension the belts on the engine and filled them with R-22. Waited an hour and check them with the sniffer. No leak found yet.
Are R-22 molecules any larger than air molecules?
Jim

Is air a molecule or a composite of elements?

I'm going to use 134 once I create a tee in the steer compartment and put a 134 valve connection along with the schrader air fitting. That puts air to the entire aux system (or freon) and I will start searching again. I don't think that anyone that has not gone through the search process can ever appreciate all the potential sources for leaks and the various subtle ways a leak can be present and still undetectible.

One thing I know for certain. I would never turn my bus over to a mechanic and ask him to find a leak. I would end up sending his kids through college and him and his wife on a trip to Hawaii and my bus would still leak.

Having a air leak free bus is a journey not a destination. Enjoy the trip.

How well I know. I worked every night for over two weeks on the floor of a cold barn getting bus #1 leak free and that included the entire suspension system. For a long time it was, but as you might guess over time the compressor ran more and more and it leaned sooner and sooner.

If I was in the Prouds I would have my people take care of my bus. We must all be nuts.

"Is air a molecule or a composite of elements?"

Mixture, not a molecule. Air composition can vary with location. Composite? Doesn't meet the definition (of many) I'm aware of. Good question, though.

I am just sitting here contemplating my taxes.

Yeah, and I am sitting here writing out bills. Guess what is getting done more? Bills or horseplay on POG?

:cool:Just think, If you owe taxes and don't pay them- you will be qualified to hold a cabinet position in the new administration. All that is necessary to make things work is say "I'm sorry".

If you for sure owe taxes and pay them : You are a Great American.

Jon,

You could add some dye to the 134, pressurize the system then go on a sightseeing tour. The product is out there and available, believe, as I recall, the leak will turn red.

I had a similar issue, turned out to be a failed one way check valve leaving the compressor...junk, how I don't know, go into the check and it produced and agonizinly slow leak...really slow.

Quote:

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Originally Posted by rfoster

:cool:Just think, If you owe taxes and don't pay them- you will be qualified to hold a cabinet position in the new administration. All that is necessary to make things work is say "I'm sorry".

If you for sure owe taxes and pay them : You are a Great American.

---

I'm sorry.

I agree with the dye, but part of the problem is that a relatively small percentage of the fittings or devices permit visibility all around the part.

At least with bubbles or a sniffer i get some visual clue, but with refrigerant as you are undoubtedly aware often times there are visual clues such as an oil stain, but like the one typically found behind the OTR compressor it is behind the clutch and not visible.

I need something that makes it really visible such as blowing bubbles or a freon sniffer to at least get me in the general area. Or I need someone to do this search mission for me. I'll supervise.

Jon,

A guy in Houston that I have been talking to about using R-22 says that there is a reason he uses 22 instead of 134. Something about one has a ? make up and the other has a ? makeup. I have not got into using refrigerant yet I have just been looking into it for a year or so. I just remember him saying that 134 doesn't work nearly as good or if at all.

I do know 134 is hard to detect. I haven't even begun to get the stuff to add the fitting for refrigerant so I will be checking to see what is going to be most effective. I also have some R12 replacement that is not freon but is propane based (I should have said hydrocarbon based). If the sniffer will pick that up I may use that. I think that will leave the system at 70 PSI at normal ambient temps. I have more homework to do.

If I do use the R12 replacement it has that distinctive propane odor and if that gets me in the area of the leak just by using my nose I am much further ahead than I am now.

There is a portable UV lamp made by Interdynamics (probably others too) that can be used to spot A/C leaks - it runs around $50 and can be bought almost anywhere.