Skip to main content ↑ ↓
Topic: Aux Air Leak 2001 (Read 567 times) previous topic - next topic

Aux Air Leak 2001

On a recent trip, the coach sat level for one month, slowly lowering but maintaining level.  Following its algorithm of letting air out. The L and R tanks went from 125 psi to zero over the month. The slide air valve was closed.  The aux compressor was  turned on only when that system pressure got to 70 psi and then it would pressurize the slide bladder tank to 90 psi and shut off. But when I did this it did not raise the coach as the coach was level enough. 

So the question became,  if the aux was not needed to level, and it was not used for the slide (bladder), what caused the aux pressure to drop over two days from 90 to 70?  Was it a leak in the aux air tank?  Seems a possibility. Maybe that check valve.

I had already followed the schematic, determined before the trip that the aux was adding air to the L and R tanks.  Identified the faulty check valves, replaced them and all was good.  So that not the problem, maybe.  If you wish to look at this in more detail, follow line 57, it goes to a fitting that splits the air off into other supply lines to the front and rear manifolds and can also add air into the L and R tanks if the valves fail (leak).  Note:  they leak much less if there is a larger pressure differential (very low on L or R tank versus the supply from aux.)

I had monitored that the aux pressure would go from 90 to 80 psi in 12 hours.  After a month, this changed to 4 hours.  So the leakage was increasing.

The solution:  In the aux regulator there is a T connection.  MOT could not detect a leak the usual way but they have a means to listen for leaks.  That T was leaking.  It is a plastic affair, better if brass.  They changed it out, leak stopped.  Also, using the audible detection instrument, then found a couple of other slow leaks that were hard to find with bubbles.  Photo of T below, a dime for perspective.

The main thing I learned here.....did not know of that T.  Did not know of the device to listen for leaks, very helpful.  The system works really well, stays level for a month even though the entire coach lowers, seems to not use air to raise a corner to level up.

Mike
2001 U320 4010 Build 5878 (Gus)
Wrangle Unlimited Toad
Nacogdoches

Re: Aux Air Leak 2001

Reply #1 –
Was at our local Fastenal store,they had similar fittings in stainless.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Aux Air Leak 2001

Reply #2 –
MOT did a fantastic job of finding and fixing MANY leaks in my air system. The best part is it now remains level as it eventually loses air.
 
Trent
Trent and Jean Eyler
2000  U295  4003  WTFE  ISC  350
Build#5603 MC#17385

Re: Aux Air Leak 2001

Reply #3 –

My coach's air leaks down in a day or 2 but not having a slide I'm not too concerned about it.  Yet.  Maybe this winter I'll look around for leaks.  In my previous Newell which had a much more complicated air system I had an Inficon Whisper ultrasonic leak detector.
Inficon 711-202-G1 Whisper Ultrasonic Leak Detector: Ultrasonic Measure:...

These work amazingly well for finding air leaks, large and small.  Or you can use kids bubbles, cheap and work well also if you can get to the tubing or fitting. 
Also the push-connect air fittings will usually leak over time.  I always replaced them with DOT compression fittings.  But don't use a stainless fitting unless it has a brass ferrule.  The stainless ferrule in a Parker or Swagelok type fitting can cut the plastic tubing.

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.
Forest & Cindy Olivier
1987 log cabin
2011 Roadtrek C210P
no longer 1999 36' U320 build #5522
2013 Rzr 570 & 2018 Ranger XP1000
2006 Lexus GX470
2011 Tahoe LT 4x4
Previous 1998 45' 2 slide Newell, 1993 39' Newell

Re: Aux Air Leak 2001

Reply #4 –
Thanks Forest...
Good to kmow about stainless and brass
Good to know about that detector, before this i had no idea of such
As for bubbles, been using that a good while but even MOT not find some with bubble...hard to get to places, very slow leaks not easily seen they say
With or withoit slide not my test, i want everything to be as should.  I know it will not stay perfect, but boy, sitting level for a month, though oversll going lower, without using the aux to raise some...that is pretty good!

Thanks, hope you two well, and that beautiful coach happy too.
Mike
2001 U320 4010 Build 5878 (Gus)
Wrangle Unlimited Toad
Nacogdoches

Re: Aux Air Leak 2001

Reply #5 –
Folivier, I was going to ask MOT where they got that device and this morning I awoke to find your post.  I'm in Las Vegas at a meeting and with a couple of clicks on your link it will be at my office before I get home.  What a world we live in.

Thanks for that.
Rick & Rhonda
2003 U320 4220  Build #6199
Was
91 36' GV 300 Caterpillar, 92 40' U280 300 Cummins, 97 36' U295 300 Cummins, 2002
U320 450 Cummins
(Guess we're hooked)

The selected media item is not currently available.