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Topic: Air leak (Read 1189 times) previous topic - next topic

Air leak

Sorry, another air leak post. In about 8 hours both gauges simultaneously go to zero. The check valves appear to work properly as  they don't change pressure when wet tank is drained. I have sprayed everything with no obvious leaks. Anyone have any ideas. Thanks
Kim McCoy
1997 270 34'

Re: Air leak

Reply #1 –
Have you checked the stairwell cover air ram? and how about the air regulators.
Mike & Donna Mariana + Angel & Rusty
2003 U295 3620
Build# 6118
2021 Jeep Wrangler 392

Re: Air leak

Reply #2 –
Yes
Kim McCoy
1997 270 34'

Re: Air leak

Reply #3 –
Quote from: zmpm01 –
Have you checked the stairwell cover air ram? and how about the air regulators.

If the protection valves are working correctly they would only let the air pressure get down to around 65 psi on the front and rear air tanks, so leak(s) are somewhere else. I am assuming that when he says both air gauges he is talking about the gauge for the front and rear tanks.

Did you check the drain valves and the fittings?
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Air leak

Reply #4 –
Yep, I guess I was thinking maybe something that would cause both tanks to loose air. The gauges move the same amount to zero.
Kim McCoy
1997 270 34'

Re: Air leak

Reply #5 –
Quote from: golfnut –
The check valves appear to work properly as  they don't change pressure when wet tank is drained.
If the check valves are sealing properly, the leak must not be upstream of those valves.

As turbojack states, if the leak was downstream from the protection valves, then your pressure gauges would stop going down (or at least pause for some time) around the 65 psi level.  Since they are not doing that, it would seem the leak is upstream from the protection valves.

This narrows the possible source of air loss down to a fairly restricted space - somewhere between the check valves and the protection valves.  Look at your air system diagram and see which air lines tie into the tanks between those valves.  Where do those air lines go?  Could the tanks themselves be leaking?  Having rust holes appear in both tanks simultaneously would be...unusual.  The condensate drain valves?  You said you checked them.

Good luck.
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: Air leak

Reply #6 –
Thanks, no luck yet. Fun Fun. NOT
Kim McCoy
1997 270 34'

Re: Air leak

Reply #7 –
Seems to me something in the braking system or if throttle is air operated. Since you have eliminated air leaks at fittings, then possibly a brake module. Have you checked brake pedal  or throttle controller in the coach.

Do you have the drawings of air system? Maybe if you posted someone may come up with an idea.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Air leak

Reply #8 –
Did you check parking brake valve and fittings?
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Air leak

Reply #9 –
You have a couple of air pressure switches that are in the piping that is fed off the line going to the brake treadle valve and park brake. These switches are known to leak at the crimp ring.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Air leak

Reply #10 –
Thanks everyone, taking a break. When I get under coach again I will take some pics. I did check parking break switch no leak detected. I didn't check other areas concerning brakes, I did check treadle valve.
Kim McCoy
1997 270 34'

Re: Air leak

Reply #11 –
Sounds like a big enough leak that you might be able to hear.
Get the air up, turn your hearing aids all the way up 😊 and go around inside and out and listen.
You might get lucky.
Hope you do.
John Duld
1995 U320C SE 40'

Re: Air leak

Reply #12 –
Could gauges be part of the problem

Re: Air leak

Reply #13 –
Speaking of air leaks, where do people buy DOT certified brake line fittings? I'm getting Sticker Shock looking at what's offered online!
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel

Re: Air leak

Reply #14 –
Fleetpride.  Go online and open an account.  They will give a discount over regular web prices
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Air leak

Reply #15 –
You may have a few check valves. Dryer exit for one and one at each tank inlet. If both tanks lose the same values. I would look near the dryer check valve for starters.  Simple way to test.  Let the air fall to 2-40# and unscrew the cartridge a little.  There should not be pressure in the dryer after it purges.  Be careful of course.
 Trace the lines and see what shares pressure ?
  My parking brake leaks pretty quickly in about 5 hrs to zero ish .
 My brake treadle valve leaks a little while running , and while parked  . 

Re: Air leak

Reply #16 –
A big bubble, the front protection valve. It is leaking out the little hole. Not sure it is enough to amount to anything.
Kim McCoy
1997 270 34'

Re: Air leak

Reply #17 –
If you haven't already, try pumping the brake pedal with coach running. 
Dan - Full timing since 2009
2003 U320 40' Tag 2 slide

Re: Air leak

Reply #18 –
With the air coming out that little hole indicates that the diaphragm has/is failing. Said another way the diaphragm has a hole in it which mean the protection valve need replacing so it will function properly.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Air leak

Reply #19 –
Would this be a proper replacement?
Kim McCoy
1997 270 34'

Re: Air leak

Reply #20 –
Dan, why are you suggesting pumping brakes? Thanks
Kim McCoy
1997 270 34'

Re: Air leak

Reply #21 –
Quote from: golfnut –
Would this be a proper replacement?

Does it cross-reference?

Part Number Collection

Reservoir Pressure Protection Valve - 1/4" NPT, 65 PSI
Haldex: 90555396
Midland: N15759DG
Meritor Wabco: 9348990060
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Air leak

Reply #22 –
Am I to assume the right tank uses same valve? Looking at that tank, it has been replaced with this valve.
Kim McCoy
1997 270 34'

Re: Air leak

Reply #23 –
Quote from: golfnut –
Am I to assume the right tank uses same valve?

Yes

Those valves should be rated to close at about 60-65 lbs.  the one listed in reply 19 it closes at 45 which leaves you little pressure to get off the road before the spring brake will set.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Air leak

Reply #24 –
Quote from: golfnut –
Dan, why are you suggesting pumping brakes? Thanks

Happened to me one time on a Bluebird coach when I was still a novice RVer.

Had camp hosted for 5 months.  When ready to depart could not build air pressure. Checked around, heard leak by treadle under front of coach.  Hit the brakes a couple of times and it resolved itself. Never happened againn.
Dan - Full timing since 2009
2003 U320 40' Tag 2 slide