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Big air leak

While driving the coach home today, I noticed that the air tanks were having a hard time topping off to 120 psi at low idle; high idle, ok.  While driving tanks were good and cycling.  When I got home, and shut down, I noticed both tanks lost air quickly.  Outside air temp is 0 f.  Any ideas as to where this leak could be?  All new airbags.  Wasn't doing this with above freezing temps.
Thanks, Mike
Mike Brady
'97 U320 SE. #5137
'13 Honda Fit
Willow Springs, MO

Re: Big air leak

Reply #1 –
my tanks only go to about 92-93 psi.. is this not good? travel light comes on about 85-88 approx..

Re: Big air leak

Reply #2 –
Hey Mike,
Just a guess, possibly the air dryer is partially stuck in the purge position. There are a number of areas that could have a problem at that temperature. Time to start checking connections.

Bob
The selected media item is not currently available.Bob & Faith Rozek
1997 U320 40'
Xtreme Remodel
2010 Scion XD

Re: Big air leak

Reply #3 –
Quote from: Robert T Rozek –
Hey Mike,
Just a guess, possibly the air dryer is partially stuck in the purge position. There are a number of areas that could have a problem at that temperature. Time to start checking connections.

Bob

But, a leak at the dryer would not drain tanks unless the check valves are bad.

That big a leak should be audible.  Fully build PSI, shut it off and go out and listen carefully.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Big air leak

Reply #4 –
Quote from: Yetch –
I noticed both tanks lost air quickly.
Agree with Brett - most likely problem is downstream of your brake air tanks.  One likely suspect is the pressure regulator that controls pressure to the front 6-pack manifold.  Not sure where it is located on your coach, but probably in the vicinity of the front and rear brake air tanks.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Big air leak

Reply #5 –
Quote from: DavidS –
my tanks only go to about 92-93 psi.. is this not good? travel light comes on about 85-88 approx..
Yes, that is a problem.  Your system air pressure should cycle between a low of about 90 psi (engine air compressor cut-in) and a high of about 120 psi (engine air compressor cut-out).  If you do not see pressures in this range, then I would suspect a faulty D2 governor.  It's a $20 part - if it malfunctions can cause BIG problems.  Search this Forum for "D2 governor" for LOTS of info.

Air Governor [ForeForums Foretravel Motorcoach Wiki]
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Big air leak

Reply #6 –
DavidS, you air pressure should go to at least 120 PSI. That's the cutout for most air governors that control the air compressor. Also what Chuck said.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Big air leak

Reply #7 –
Water frozen somewhere in the air system ?
Can you get it inside (heated building) overnight?
If that cures it dran the airtanks and press on.
John Duld
1995 U320C SE 40'
 

Re: Big air leak

Reply #8 –
If it ice you will need to service the air dryer. First you need to fine out what is leaking.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport