Air system leaks

[Doubledoc]

We have had a problem with accessory air system leaking. It was found that a connector (one of six) in the air system for the slide locks was leaking and replaced. Things got better. However, air started to leak again. The 110v ac compressor would come on every 30 minutes (air pressure range 120 psi down to 100psi ). While in storage I turned the 110V ac air compressor off. After a few days, the rear road side air bags had lost air and dropped the coach down at that corner. Starting the engine pumped up everything and all worked ok, except the accessory air which would drop to such a low level overnight that the toilet would not operate and the coach remained level.

Is it possible that the air leak in the air bags is draining the accessory air supply as well? The whole air suspension does not drain down.
I plan to repair suspension air and have the remaining five slide connectors checked or replaced.
Any thoughts ?

[DonB]

Is the M450 accessory air like the M380? The M380 has a separate small tank in the front left that is fed from the main system, or from a 12V pump. That small tank serves the slides, and on mine also the stepwell cover. I don't have an air toilet, but it probably would be the one for that as well.

I don't want to offer possible trouble-shooting ideas without knowing if the systems are the same.

[Doubledoc]

As far as know, the accessory air system has a tank which is fed from 110v ac air comp,12 v dc air comp, or the main engine air system. It supplies air for air horn,door entry safety lock, entry slide cover, toilet and the slide locks, and the Hadley leveling system. The 12v dc comp operates between 60psi and 80 psi, the 110v ac comp operates between 100psi and 120 psi, and the engine air comp operates at 125 psi. The various systems that use air operate at different minimum air pressures.

It sounds like the M450 is similiar to the M380.

[DonB]

Yes, it does sound similar. I had major leak-down problems with my system. I determined the following:

There are two check-valves on the small tank. One is on the input from the main system, and the other is on the input from the 12VDC pump. Both leaked. They are both in elbows. I did not replace them, but rather added an in-line check valve before each of the offending valves. I used http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

I found that *every* one of the threaded nipples into the tank were leaking, with the sealant all dried out. I did not get an indication with an ultrasonic detector, but it was obvious using gas-leak detector solution. I ended up removing the tank to make it easier to get the nipples out and re-goop them up.

I found that several of the push-to-fit connectors on and around the tank and pumps leaked. I replaced all of them.

The worst push-to-fit leak (found by isolation using ball valves on individual lines) was on the pair of valves that operate the entry slide cover. On the M380 those are in a floor-level trace behind the passenger seat. Because you have a slide there I don't know where the valves will be, but they should be easy to hear when operating the slide.

After fixing all of these leaks last fall, running the 110VAC pump once daily results in a 24-hour drop to 50PSI on the accessory system. The main coach drops to zero in just a couple of hours, but the check valves work well. I installed a dash gauge that gives pressure on the tank, and on the coach auxiliary, so I can tell what happens.

I would definitely start with the check valves! I found that they were the big problem again by using a ball valve on that larger line from the coach. A couple of ball valves with push-to-fit connectors and a bit of extra line are great diagnostic tools for this problem.

[Doubledoc]

Thanks, Don. Very useful ideas. We will start with the connectors , check valves and fittings on tank.
Jim

[Doubledoc]

The check vakves were tested and proved to be OK. The problem was found with the elbows which are fixed on one leg and can swivel on the other. They are used because it makes assembly much easier. However the swivel is a weak link and often fails. The tech said there are 20-30 such elbows with a swivel thru out the accessory systems on our coach. He had replaced one before on the slide lock system.

Maybe I will make it a winter project to replace all those elbows. We will wait and see how the fix works out.
Jim

[G_man]

Jim,

I had similar problems on my '99 LXi (before we bought the M450). The culprits were check valves that were bleeding auxiliary tank air back into the main system. Replaced them with "low crack pressure" checks with a nylon looking check. No more problems. BTW, I took apart the old ones and they were a corroded mess inside. McMaster Carr has all the parts, connectors, tubing, check valves, etc.

[Lee Davis]

I have a question about the engine air compressor. It seems to take longer to air up than it used to (about 10 min when it used to ba about 5 min) and now when driving down a level road and not using any brakes (which use air of course) my compressor cycles about every 8-10 minutes to pump the air back up from about 100 psi to about 120 psi. Is that normal or does that mean I am losing air somewhere and it is cycling too often.

Thanks,

Lee

[Crit Bliss]

Air it up and shut it down so you can listen for leaks, see if the gauges fall rapidly

[Bill Pape]

The air pressure gages are on each brake tank only.
You may have a leak anywhere or everywhere, except the brakes. When the governor sees less than about 90, even if there is 100 on the gage, the compressor will recharge all tanks back up to 120.
My guess is you have an air leak.